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Reference Manual’s Chapter on Expert Witness Testimony Admissibility – Part 4

March 5th, 2026

In the district court, Judge George O’Toole conducted a pre-trial hearing over four days, and heard testimony from Smith and Cranor, as well as from defense expert witnesses. Judge O’Toole’s published opinion carefully and accurately stated the facts, the applicable law, and presented a well-reasoned judgment as to why Smith’s opinion was not admissible under Rule 702. Without admissible opinions on general causation to support Milward’s case, Judge O’Toole granted summary judgment to the defendants.

Milward appealed the judgment. A panel of judges in the First Circuit heard argument, and reversed in an opinion that is riddled with serious errors.[1] In reviewing the district court’s application of Rule 702, the panel, in an opinion written by Chief Judge Lynch, credulously accepted most of Smith’s and Cranor’s arguments that an ill-defined WOE approach is acceptable method of guiding scientific judgment. Cranor equated WOE, as used by Smith, to the approach that Sir Austin Bradford Hill described, in 1965, for identifying causal associations from epidemiologic data.[2] Chief Judge Lynch’s opinion tracked accurately Cranor’s and Milward’s lawyers’ misrepresentations about Sir Austin’s paper:

“Dr. Smith’s opinion was based on a ‘‘weight of the evidence’’ methodology in which he followed the guidelines articulated by world-renowned epidemiologist Sir Arthur [sic] Bradford Hill in his seminal methodological article on inferences of causality. See Arthur [sic] Bradford Hill, The Environment and Disease: Association or Causation?, 58 Proc. Royal Soc’y Med. 295 (1965).

Hill’s article explains that one should not conclude that an observed association between a disease and a feature of the environment (e.g., a chemical) is causal without first considering a variety of ‘viewpoints’ on the issue.”[3]

The quoted language from the First Circuit opinion, which twice refers to “Arthur Bradford Hill,” rather than Austin Bradford Hill, may suggest that neither Chief Judge Lynch nor his judicial colleagues and their law clerks read the classic paper. An even stronger indicator that the appellate court did not actually read this paper is evidenced in the court’s equating WOE to Bradford Hill viewpoints, without consideration of the necessary predicate for those nine viewpoints. In his short paper, Sir Austin clearly spelled out that there was a foundation needed before parsing the nine viewpoints:

“Disregarding then any such problem in semantics we have this situation. Our observations reveal an association between two variables, perfectly clear-cut and beyond what we would care to attribute to the play of chance. What aspects of that association should we especially consider before deciding that the most likely interpretation of it is causation?”[4]

Whatever Sir Arthur had to say about the matter, Sir Austin defined the starting point of causal analysis as an association free of invalidating bias and random error. The Milward decision ignored this all important predicate for assessing the various considerations that might allow for a valid association to be considered a causal association.[5] The resulting abridgement was a failure of scientific due process that distorted the Bradford Hill paper.

The First Circuit amplified its error when it asserted that from the nine considerations “no one type of evidence must be present before causality may be inferred.”[6] Although Sir Austin said something similar, one of the considerations he noted was “temporality,” in which the putative cause must come before the effect.  Most scientists would consider this consideration to be essential, unless they were observing events that were moving faster than the speed of light. The other eight considerations are more dependent upon context of the exposures and outcomes of interest, but surely strength and consistency of the clear-cut association across multiple studies is an extremely important consideration.

The First Circuit proceeds from misreading Sir Austin’s paper to misunderstanding another paper invoked by Cranor and by Milward’s lawyers. Carelessly tracking Cranor, the appellate court suggested that there was no “hierarchy of evidence”:

“For example, when a group from the National Cancer Institute was asked to rank the different types of evidence, it concluded that ‘‘[t]here should be no such hierarchy.’’ Michele Carbon [sic] et al., Modern Criteria to Establish Human Cancer Etiology, 64 Cancer Res. 5518, 5522 (2004); see also Sheldon Krimsky, The Weight of Scientific Evidence in Policy and Law, 95 Am. J. Pub. Health S129, S130 (2005).”[7]

This quoted language from the Milward opinion shows how slavishly and credulously the court adopted and regurgitated plaintiff’s argument. Sheldon Krimky was actively involved with SKAPP, and his article was presented at the SKAPP-funded Coronado Conference, discussed earlier in this series. Krimsky actually acknowledged that although “the term [WOE] is applied quite liberally in the regulatory literature, the methodology behind it is rarely explicated.”

As for the article by Carbon [sic], this publication never rejected a hierarchy of evidence. The court’s language, quoted above, follows immediately after the court’s discussion of Sir Austin’s nine types of corroborating evidence that would support the causal interpretation of an association. As such, the court seems to imply, incorrectly, that there was no hierarchy of these considerations.[8]

The court’s language also suggests that the quoted language came from the National Cancer Institute (NCI), but its provenance is quite different. The cited article’s lead author, Michele Carbone (not Carbon), was reporting on a workshop hosted by the NCI at an NCI building; it was not an official NCI event or publication. The NCI did sponsor or conduct the meeting, and Carbone’s paper was not an official statement of the NCI. Carbone’s paper was styled “Meeting Report,” and published as a paid advertisement in Cancer Research, not in the Journal of the National Cancer Institute as a scholarly article.

The discipline of epidemiology was not strongly represented at the meeting; most of the chairpersons and scientists in attendance were pathologists, cell biologists, virologists, and toxicologists. The authors of the meeting report reflect the interests and focus of the scientists in attendance. The lead author, Michele Carbone, a pathologist at the University of Hawaii, was an enthusiastic proponent of Simian Virus 40 as a cause of mesothelioma, a hypothesis that has not fared terribly well in the crucible of epidemiologic science.

The cited article did report some suggestions for modifying Bradford Hill’s criteria in the light of modern molecular biology, as well as a sense of the group that there was no “hierarchy” in which epidemiology was at the top of disciplines.  The group definitely did not address the established concept that some types of epidemiologic studies are analytically more powerful to support inferences of causality than others — the hierarchy of epidemiologic evidence. The group also did not address or reject a ranking of importance of Bradford Hill’s nine viewpoints. There was nothing remarkable about the tumor biologists’ statement that in some cases causality can be determined by careful identification of genetic inheritance or molecular biological pathways. There was no evidence of this sort in the Milward case, and the citation by Cranor and Milward’s lawyers was nothing more than hand waving.

Carbone’s meeting report summarizes informal discussion sessions at the 2003 meeting.  Those in attendance broke out into two groups, one chaired by Brook Mossman, a pathologist, and the other group chaired by Dr. Harald zur Hausen, a virologist. The meeting report included a narrative of how the two groups responded to twelve questions. Drawing from plaintiff’s (and Cranor’s) argument, the court’s citation to this meeting report is based upon one sentence in Carbone’s report, about one of twelve questions:

“6. What is the hierarchy of state-of-the-art approaches needed for confirmation criteria, and which bioassays are critical for decisions: epidemiology, animal testing, cell culture, genomics, and so forth?

There should be no such hierarchy. Epidemiology, animal, tissue culture and molecular pathology should be seen as integrating evidences in the determination of human carcinogenicity.”[9]

Considering the fuller context of the meeting, there is nothing particularly surprising about this statement.  The full question and answer in the meeting report does not even remotely support the weight given to it by the court. There was quite a bit of disagreement among meeting participants over criteria for different kinds of carcinogens, as seen the report on another question:

“2. Should the criteria be the same for different agents (viruses, chemicals, physical agents, promoting agents versus initiating DNA-damaging agents)?

There were different opinions. Group 1 debated this issue and concluded that the current listing of criteria should remain the same because we lack sufficient evidence to develop a separate classification. Group 2 strongly supported the view that it is useful to separate the biological or infectious agents from chemical and physical carcinogens due to their frequently entirely different mode of action.”[10]

Carbone and the other authors of the meeting report noted the importance to epidemiology for general causation, while acknowledging its limitations for determining specific causation:

“Concerning the respective roles of epidemiology and molecular pathology, it was noted that epidemiology allows the determination of the overall effect of a given carcinogen in the human population (e.g., hepatitis B virus and hepatocellular carcinoma) but cannot prove causality in the individual tumor patient.”[11]

Clearly, the report was not disavowing the necessity for epidemiology to confirm carcinogenicity in humans. Specific causation of Mr. Milward’s APML was irrelevant to his first appeal to the First Circuit. Carbone’s report emphasized the need to integrate epidemiologic findings with molecular biology; it did not suggest that epidemiology was not necessary or urge that epidemiology be ignored or disregarded:

“A general consensus was often reached on several topics such as the need to integrate molecular pathology and epidemiology for a more accurate and rapid identification of human carcinogens.”[12]

                 * * * * *

“Ideally, before labeling an agent as a human carcinogen, it is important to have epidemiological, experimental animals, and mechanistic evidence (molecular pathology).”[13]

The court’s implication that there was “no hierarchy of evidence” is unsupported by the meeting report. The suggestion that WOE allows some loosey-goosey, ad hoc, unstructured assessment of diverse lines of evidence is rejected in the meeting report with a careful admonition about the lack of validity of some animal models and mechanistic research:

“Moreover, carcinogens and anticarcinogens can have different effects in different situations. As shown by the example of addition of β-carotene in the diet, β- carotene has chemopreventive effects in many experimental systems, yet it appears to have increased the incidence of lung cancer in heavy smokers. Animal experiments can be very useful in predicting the carcinogenicity of a given chemical. However, there are significant differences in susceptibility among species and within organs in the same species, and differences in the metabolic pathway of a given chemical among human and animals could lead to error.”[14]

Inference to the Best Explanation

The First Circuit asserted that “no serious argument can be made that the weight of the evidence approach is inherently unreliable.”[15] As discussed above, this assertion is demonstrably false. In his testimony at the Rule 702 pre-trial hearing, Cranor classified WOE as based upon “inference to the best explanation,” and the First Circuit obsequiously accepted this claim. In articulating and accepting Cranor’s reduction of scientific method to IBE, the appellate court seemed unaware that IBE as an epistemic theory has been roundly criticized. In a very general sense, IBE draws on Charles Pierce’s description of abduction as a mode of reasoning, although many writers have been eager to distinguish abduction from IBE. Bas van Fraassen criticized IBE as lacking merit as a mode of argument in a way germane to Cranor’s presentation of the notion, and the First Circuit’s uncritical acceptance:

“As long as the pattern of Inference to the Best Explanation—henceforth, IBE—is left vague, it seems to fit much rational activity. But when we scrutinize its credentials, we find it seriously wanting.”[16]

The IBE approach raises thorny problems of knowing how to discern the best explanation, or how to tell whether an explanation is simply the best of a bad lot. Other philosophers of science have questioned why explanatoriness should matter as opposed to predictive ability and resistance to falsification upon severe or robust testing.

In the hands of Smith and Cranor, these philosophical quandries become largely beside the point. For Smith and Cranor IBE becomes telling just so stories, which transform “but for” causation into “could be” causation. Drawing directly from Cranor, the Circuit Court explained that an inference to the best explanation involves six general steps for scientists:

“(1) identify an association between an exposure and a disease,

(2) consider a range of plausible explanations for the association,

(3) rank the rival explanations according to their plausibility,

(4) seek additional evidence to separate the more plausible from the less plausible explanations,

(5) consider all of the relevant available evidence, and

(6) integrate the evidence  using professional judgment to come to a conclusion about the best explanation.”[17]

Of course assessing causation requires judgment, but Cranor and Smith radically abridge the process of judging by eliminating:

  • the robust testing of, and attempts to falsify, hypotheses,
  • the weighting of study designs,
  • the pre-specification of kinds of studies to be included or excluded, the assignment of weights to different kinds and qualities of studies, and
  • the pre-specification of criteria of study validity, experimental design, consistency, and exposure-response.

The vague, contentless IBE and WOE, in the hands of Smith, operates just as van Fraassen anticipated. With Cranor’s “philosophizing,” IBE creates a permission structure to reach any desired conclusion. Indeed, Cranor’s approach makes no allowance for when careful scientists withhold judgment because the evidence is inadequate to the task. Furthermore, Cranor’s approach and the Milward decision would cheerily approve cherry picking of studies and data within studies, post hoc weighing of evidence, and even fabricating and rejiggering of evidence, all of which was on display in Smith’s for-litigation opinion.

The First Circuit uttered its mantra of approval of Smith’s scientific delicts in language that became the target of the revision of Rule 702 in 2023:

“the alleged flaws identified by the [district] court go to the weight of Dr. Smith’s opinion, not its admissibility. There is an important difference between what is unreliable support and what a trier of fact may conclude is insufficient support for an expert’s conclusion.”[18]

Earlier in its opinion, the appellate court quoted from the version of Rule 702 in effect when it heard the appeal:

“if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.”[19]

Sufficiency, reliability, and validity were all preliminary questions to be decided by the court as part of its gatekeeping responsibility.  The appellate court simply ignored the law in its decision to green light Smith’s testimony.

                    (to be continued)

[1] Milward v. Acuity Specialty Products Group, Inc., 639 F.3d 11 (1st Cir. 2011), cert. denied sub nom., U.S. Steel Corp. v. Milward, 565 U.S. 1111 (2012).

[2] Austin Bradford Hill, The Environment and Disease: Association or Causation?, 58 PROC. ROYAL SOC’Y MED. 295 (1965).

[3] Milward, 639 F.3d at 17.

[4] Id. at 295.

[5] See Frank C. Woodside, III & Allison G. Davis, The Bradford Hill Criteria: The Forgotten Predicate, 35 THOMAS JEFFERSON L. REV. 103 (2013).

[6] Milward, 639 F.3d at 17.

[7] Id. (internal citations omitted).

[8] The Reference Manual chapter on medical testimony carefully discusses the hierarchy of evidence as it factors into the assessment of medical causation. John B. Wong, Lawrence O. Gostin & Oscar A. Cabrera, Reference Guide on Medical Testimony, in National Academies of Sciences, Engineering and Medicine & Federal Judicial Center, REFERENCE MANUAL ON SCIENTIFIC EVIDENCE 687, 723 -24 (2011); John B. Wong, Lawrence O. Gostin, & Oscar A. Cabrera, Reference Guide on Medical Testimony, in National Academies of Sciences, Engineering and Medicine & Federal Judicial Center, REFERENCE MANUAL ON SCIENTIFIC EVIDENCE 1105, 1150-52 (4th ed. 2025). Interestingly, the chapter on epidemiology in the third edition of the Reference Manual cited to the Carbone workshop with apparent approval, but the same chapter in the fourth edition has dropped the reference. Compare Michael D. Green, D. Michal Freedman & Leon Gordis, Reference Guide on Epidemiology, in National Academies of Sciences, Engineering and Medicine & Federal Judicial Center, REFERENCE MANUAL ON SCIENTIFIC EVIDENCE 549, 564 n.48 (3rd ed. 2011) with Steve C. Gold, Michael D. Green, Jonathan Chevrier, & Brenda Eskenazi, Reference Guide on Epidemiology, in National Academies of Sciences, Engineering and Medicine & Federal Judicial Center, REFERENCE MANUAL ON SCIENTIFIC EVIDENCE 897 (4th ed. 2025).

[9] Carbone at 5522.

[10] Carbone at 5521.

[11] Carbone at 5518 (emphasis added).

[12] Carbone at 5518.

[13] Carbone at 5519.

[14] Carbone at 5521.

[15] Milward, 639 F.3d at 18-19.

[16] Bas van Fraassen, LAWS AND SYMMETRY 131 (1989).

[17] Milward, 639 F.3d at 18.

[18] Milward, 639 F.3d at 22.

[19] Milward, 639 F.3d at 14.

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The First Daubert Motion

February 20th, 2026

As every school child knows, or at least every law student in the United States knows, Daubert was a Bendectin case. The plaintiff claimed that his mother’s use of Bendectin, a prescription anti-nausea medication, during pregnancy caused him to be born with a major limb reduction defect.

Filed in 1984, the Daubert case was pending, in summer 1989, before Judge Earl Ben Gilliam, in the Southern District of California. A trial date was approaching, and a deadline for motions for summary judgment. The first Daubert motion was filed in August 1989, in Daubert v. Merrell Dow Pharmaceuticals, Inc.[1] It was a motion for summary judgment, not a motion specifically to exclude plaintiffs’ expert witness’s proffered testimony.

By the time of the first Daubert motion, the plaintiff was relying upon the anticipated testimony of John Davis Palmer, M.D. For the time, John Davis Palmer was not an unlikely expert witness. Although Palmer practiced internal medicine, he had a doctorate in pharmacology. Palmer, however, had no experience studying Bendectin, and no real expertise in epidemiology. He had never designed or published an epidemiologic study, and he had never done any kind of research on Bendectin. The standard for qualifying an expert witness, even in federal court, has always been very low, and thus not an effective way to police the quality of scientific evidence.

Palmer was a rather late substitute for expert witnesses previously listed by the plaintiff. Alan Kimball Done, a pediatrician, had been the main warhorse of the Bendectin plaintiffs, but he was withdrawn by plaintiff’s counsel after he was found to have committed perjury about his academic credentials in another Bendectin case.[2]

Plaintiff also needed to drop another expert witness, William Griffith McBride, who had been a star in plaintiff’s counsel’s stable. McBride helped show the teratogenicity of thalidomide in the early 1960s,[3] and his work in the Bendectin litigation gave these dodgy cases some patina of respectability. In 1988, however, McBride was accused of fraud, for which he would eventually lose his medical license.[4] McBride also chose, rather improvidently, to sue journalists, journals, and Merrell Dow executives, for reporting his rather extensive fees, only to lose that litigation.[5] When plaintiff’s counsel withdrew McBride, plaintiff was left with only Dr. Palmer to serve as plaintiff’s sole expert witness on both general and specific causation.

At the time that the first Daubert motion was filed, manufacturer Merrell Dow had voluntarily withdrawn Bendectin from the market, without any suggestion from the FDA that this action was necessary or in the public interest. The manufacturer had also enjoyed considerable success in court. The company had tried a case that consolidated the general causation claims of over 800 plaintiffs, to a defense jury verdict, in 1985, before Chief Judge Carl Rubin, of the Southern District of Ohio.[6] Despite some isolated trial losses, the company was vindicated in three federal circuits at the time its lawyers filed the “Daubert” motion.[7] The First, Fifth, and District of Columbia Circuits of the United States Court of Appeals, had all held that the plaintiffs’ case was legally insufficient to sustain a verdict against the defendant, or that the expert testimony involved was inadmissible.

In the Daubert case, Merrell Dow Pharmaceuticals was represented by the law firm Dickson, Carlson & Campillo. The important task of drafting the motion for summary judgment landed on the desk of a first year associate, Pamela Yates, who is now a partner at Arnold & Porter. Given that Merrell Dow had succeeded in other appellate courts, the task may have seemed straight forward, but the legal theories were actually all over the map.

The first Daubert motion was not styled as a motion to exclude expert witness opinion testimony, but rather as a motion for summary judgment, pursuant to Federal Rule of Civil Procedure 56, on the issue of causation. Merrell Dow’s supporting brief did not clearly invoke the distinction between general and specific causation, which distinction was not widely drawn until later in the 1990s. The supporting brief implicitly addressed both general and specific causation.

At the time that the first Daubert motion was made, there was no clear consensus of precedent that identified the source of support for a trial court’s ruling peremptorily on a weak evidentiary display on the causation issue. The evidence supporting the defense expert witnesses’ opinion that Bendectin had not been shown to cause birth defects generally and limb reduction defects specifically was strong. For all major congenital defects, there had been no change in overall incidence for the years in which Bendectin was marketed. Such an ecological argument usually has no validity, but in the case of Bendectin, for several years, roughly half of all pregnant women used the medication. When the medication was abruptly withdrawn,[8] not because of the science but because of the cost of the litigation, the rate of birth defects remained unaffected. The great majority of birth defects have no known cause, and there was no scientific consensus that Bendectin caused birth defects; indeed by 1989, the nearly universal consensus was that Bendectin did not cause birth defects.[9]

There were also many analytical epidemiologic studies, which both individually or in combination failed to support a conclusion of causation.

In the face of the defense’s affirmative evidence, the plaintiff relied upon a potpourri of evidence:

1) chemical structure activity analysis;

2) in vitro (test tube) studies;

3 ) in vivo studies (animal teratology) studies; and

4) reanalysis of epidemiology studies.

Plaintiff’s lead counsel Barry Nace[10] had concocted this potpourri approach, which he called “mosaic theory,” and which might more aptly be called the tsemish or the shmegegge theory.[11] Whatever Nace called it, he fed it to his expert witness to argue that:

“Like the pieces of a mosaic, the individual studies showed little or nothing when viewed separately from one another, but they combined to produce a whole that was greater than the sum of its parts: a foundation for Dr. Done’s opinion that Bendectin caused appellant’s birth defects.”[12]

Although philosopher Harry Frankfurt had not yet written his seminal treatise on the subject, most courts saw that this was bullshit, which tends to result “whenever a person’s obligations or opportunities to speak about some topic exceed his knowledge of the facts that are relevant to that topic.”[13]

In addition to favorable opinions from the First, Fifth, and District of Columbia Circuits, Merrell Dow had a favorable Zeitgeist working in its favor. The plaintiff-friendly influential judge, Judge Jack Weinstein, had rolled up his sleeves and taken a hard look at the plaintiffs’ scientific evidence in the Agent Orange litigation. Judge Weinstein found that evidence wanting in an important opinion in 1985.[14] Although the alleged causal agent in Agent Orange was not Bendectin, Judge Weinstein recognized that epidemiological studies were, in a similar medico-legal context, “the only useful studies having any bearing on causation.[15] Judge Weinstein relied heavily upon Federal Rule of Evidence Rule 703, which governed what inadmissible studies expert witnesses could rely upon, to whittle down the reliance list of plaintiffs’ expert witnesses before declaring their opinions too fragile to support a reasonable jury’s verdict in favor of plaintiffs.

More generally, discerning members of the legal system were reaching the end of their tolerance for the common law laissez-faire approach to expert witness evidence. In 1986, the Department of Justice issued a report that explicitly called for meaningful judicial gatekeeping of expert witnesses.[16] And in that same year, 1986, Judge Patrick Higginbotham wrote an influential opinion, in which he warned that expert witness opinion testimony was out of control, with expert witnesses becoming mouth pieces for the lawyers and advocates of policy beyond their proper role. Judge Higginbotham observed that trial judges (with support from appellate court judges) had a duty to address the problem by policing the soundness of opinions proffered in litigation, and to reject the system’s reliance upon expert witnesses simply because they “say[] it is so:”[17]

“we recognize the temptation to answer objections to receipt of expert testimony with the short hand remark that the jury will give it ‘the weight it deserves’. This nigh reflective explanation may be sound in some cases, but in others it can mask a failure by the trial judge to come to grips with an important trial decision. Trial judges must be sensitive to the qualifications of persons claiming to be experts … . Our message to our able trial colleagues: It is time to take hold of expert testimony in federal trials.”[18]

Although Merrell Dow had a substantial tailwind behind its motion for summary judgment, there was no one clear theory upon which it could rely. Some of the Bendectin appellate court opinions were based upon the insufficiency of the plaintiffs’ expert witness evidence, on the basis of the entire record after trial. The evidence in Daubert was virtually the same if not more restricted than what was of record in some of those appellate court cases. The ecological evidence was clear.

Some of the judgments relied upon by Merrell Dow were based upon the Frye test, and some were based upon Rule 703, which addresses what kinds of otherwise inadmissible evidence expert witnesses may rely upon in formulating their opinions. Finally, some courts, such as Fifth Circuit in In Re Air Crash Disaster at New Orleans, were beginning to see Rule 702 as the source of their authority to control wayward expert witness opinion testimony.

Merrell Dow advanced multiple lines of analyses to show that plaintiffs cannot establish causation based upon the then current scientific record. The first Daubert motion had no clear line of authority, and so, understandably, it cast a wide net on all available potential legal rules and doctrines to oppose the plantiff’s potpourri Bendectin causation theory. The motion harnessed precedents based upon sufficiency of the plaintiffs’ proffered expert witness, Federal Rules 702 and 703, as well as the 1923 Frye case.[19]

The cases that invoked Frye doctrine presented several interpretative problems. Frye was a criminal case that prohibited expert witnesses from testifying about their interpretations of the output of a mechanical device. The Frye case’s insistence upon general acceptance, when imported into a causation dispute in a tort case, was ambiguous as to what exactly had to be generally accepted: the specific causal claim, or the method used to reach the causal claim, or the method used as applied to the facts of the case. Furthermore, Frye’s requirement of general acceptance was not explicitly incorporated into either Rule 702 or 703, when promulgated in 1975.[20]

Merrell Dow had ample evidence that there was no general acceptance of the plaintiff’s causal claim, but its counsel also showed that by applying generally accepted methodology, scientists could not reach the plaintiff’s causal conclusion, and no scientist outside of the litigation had done so. In particular, there was general acceptance of the propositions that non-human in vivo and in vitro teratology experiments have little if any predictive ability for human outcomes. Because randomized controlled trials were never an option for testing human teratogenicity, observational epidemiology was required, and the available studies were largely exonerative. Only by post-publication data dredging and manipulation was plaintiffs’ expert witness Palmer (following what Shann Swan had done in previous cases) able to raise questions about possible associations. Plaintiff’s expert witness Palmer could not show that these manipulations were a generally accepted method for interpreting or re-analyzing published studies.

In its last point, the first Daubert motion also maintained that the standard for medical causation required that the relevant relative risk exceed two.[21] As noted, the brief did not distinguish general from specific causation, a distinction that had not entered the legal lexicon fully in 1989. The brief’s citation to swine-flu cases, however, clarifies the nature of Merrell Dow’s argument. In the swine-flu litigation, the United States government assumed liability for adverse effects of a vaccine for swine flu. The government recognized that within a certain time window after vaccination, patients had more than a doubled risk of Guillain-Barré syndrome (GBS), an autoimmune neurological condition. The government refused compensation for claimants outside that window. Merrell Dow relied heavily upon one swine flu case, Cook v. United States, which articulated and applied the principle:

“Wherever the relative risk to vaccinated persons is greater than two times the risk to unvaccinated persons, there is a greater than 50% chance that a given GBS case among vaccinees of that latency period is attributable to vaccination, thus sustaining plaintiff’s burden of proof on causation.”[22]

In other words, the government had conceded that the swine-flu vaccine could cause GBS in some temporal situations, but not others. The magnitude of the causal association had been quantified in relative risk terms by epidemiologic studies. Only for those claimants vaccinated in time windows with relative risks greater than two could courts conclude that GBS was, more likely than not, caused by vaccination.

Unlike the federal government in the swine-flu GBS litigation, Merrell Dow was not, however, conceding general causation for any exposure scenarios. The first Daubert motion can only be read to deny general causation, but to explain further that even if the court were to assume, arguendo, that Bendectin causes limb reduction deficits based upon Palmer’s schmegegge and Swan’s re-jiggered risk ratios, that there would still be no proper inference that Bendectin more likely than not caused Jason Daubert’s birth defects.

In response to these arguments, the plaintiff’s counsel argued their mosaic, potpourri, schmegegge theories. Although plaintiffs were down to Dr. Palmer, they filed transcripts and affidavits from a host of other expert witnesses, from previous Bendectin cases.

As for the legal rules of decision, Barry Nace, on behalf of plaintiffs, argued that Rule 703 had “absorbed” the Frye rule. Having been shown to be qualified under the minimal standard of Rule 702, these expert witnesses then satisfied Rule 703 by relying upon “scientific evidence” of the sort that experts in their field rely upon, even if other scientists would not rely upon such evidence in support of a conclusion. Otherwise those expert witnesses were unrestrained by the law, and they were free to assess their relied upon facts and data as sufficient to show that Bendectin probably causes birth defects and that Bendectin caused Jason Daubert’s birth defects. Nace argued that as long as expert witnesses, properly qualified, offered relevant opinions, based upon “things of science,” they could opine that the earth was flat, and it was for the jury to sort out whether to believe them.

Judge Earl Gilliam found Nace’s position untenable, and granted summary judgment later in 1989.[23] Interestingly Judge Gilliam’s opinion in the district court never cited Federal Rule of Evidence 702. Instead, the opinion pointed to Rule 703, as restricting evidence, even if “science,” unless the proponent showed that the underlying principle had gained general acceptance in the relevant field.[24] Opinions not based upon facts or data “of a type reasonably relied upon by experts in the particular field” would be confusing, misleading, and unhelpful, and thus inadmissible. The reference to helpfulness might perhaps be taken as an implicit invocation of Rule 702.

Judge Gilliam had the benefit of the Circuit decisions in Brock, Richardson, and Lynch, with their various holdings of insufficiency or inadmissibility of plaintiffs’ expert witness evidence. In particular, Judge Gilliam cited Brock for the proposition that trial courts must “critically evaluate the reasoning process by which the experts connect data to their conclusions in order for courts to consistently and rationally resolve the disputes before them.”[25] Following Judge Weinstein on Agent Orange, and the previous federal decisions on Bendectin, Judge Gilliam observed that causation in the Bendectin cases could be established, under the circumstances of plaintiffs’ evidentiary display, only through reliance upon epidemiologic evidence. Dr. Done’s schmeggege, concocted as it was by Barry Nace, would not get plaintiffs to a jury.

Judge Gilliam went further to point out that some of plaintiffs’ proffer did not even purport to claim causation. Shanna Swan’s prior testimony asserted that Bendectin was “associated” with limb reduction. Jay Glasser, a specialist in biostatistics, epidemiology and biometry had opined that “Bendectin is within a reasonable degree of epidemiological certainty associated with congenital disorders, including limb defects.” Dr. Johannes Thiersch, a specialist in pathology and pharmacology, proclaimed that “structure analysis” was “of great interest.”[26] In other words, there was a good deal of true, true, but immaterial opinion in what Mr. Nace had thrown over the transom, in opposition to the motion for summary judgment.

Nace appealed, and the Daubert case was argued to the Ninth Circuit in 1991. In a short opinion by Judge Kozinski, the appellate court affirmed the judgment below.[27] The affirmance did not mention Rule 702; rather it relied upon the decisions of other Circuits, in which the plaintiffs’ evidentiary display had been found insufficient to sustain a reasonable jury verdict.

Judge Kozinski’s opinion tilted towards Rule 703 and the Frye standard in citing to cases that stated, based upon Frye, that expert witnesses must use generally accepted techniques from the scientific community. As a legal determination, the determination of general acceptance vel non was a legal determination reviewable de novo. For its de novo decision on general acceptance, the Ninth Circuit relied upon the cases coming from the First, Fifth, and District of Columbia Circuits,[28] and of course, the record below.

By 1991, another Circuit, the Third, had weighed in on the same evidentiary display, when it reversed summary judgment for Merrell Dow, and remanded for reconsideration under the Third Circuit’s approach to Rule 702. Judge Kozinski declared that the Third Circuit’s approach was not followed in the Ninth Circuit, and proceeded to ignore the DeLuca case.[29]

Judge Kozinski treated the insufficiency and the invalidity of the Nace/Done schmeggege theory as legal precedent, and thus the court’s opinion gave very little attention by way of expository description or explanation of the problems with the four factors (in vitro, in vivo, structure analysis, and re-analysis of epidemiologic studies). As Judge Kozinski put the matter:

 “For the convincing reasons articulated by our sister circuits, we agree with the district court that the available animal and chemical studies, together with plaintiffs’ expert reanalysis of epidemiological studies, provide insufficient foundation to allow admission of expert testimony to the effect that Bendectin caused plaintiffs’ injuries.”[30]

And thus, summary judgment was proper in Daubert. Judge Kozinksi, like Judge Gilliam in the district court, never reached the specific causation argument that involved risk ratios less than two.

Some of the Circuit court cases relied upon by Judge Kozinski delved into the invalidity of these methods for determining the causes of human birth defects. The Lynch decision explored in some detail the Shanna Swan made-for-litigation rejiggering of a study based upon data from the Metropolitan Atlanta Congenital Defects Program, which included a challenge to whether it could be reasonably relied upon (Rule 703), as well as its pretense to support a scientific conclusion (Rule 702).[31] Later commentators would skirt the validity issue by asserting that re-analysis, in the abstract, is not impermissible or invalid, without addressing the specific issues discussed in the reported decisions. Other commentators have misrepresented Swan’s re-analysis as a meta-analysis, which it was not.

Some commentators have complained that the defense in Daubert made too much of the lack of statistical significance. Their complaint, in the abstract, might have some salience. In some contexts, an isolated and elevated risk ratio greater or less than one may well have important information, even if the p-value is a bit above 0.05. The lack of statistical significance at the conventional five percent, however, conveys important information about the finding’s imprecision, especially when there was a large dataset to evaluate. In 1994, a meta-analysis was published that found a summary estimate of all birth defects in the available epidemiologic studies to be an odds ratio of 0.95 (95% C.I., 0.88-1.04), and the summary estimate for limb reduction defects to be an odds ratio 1.12 (95% C.I., 0.83-1.48).[32]

[1] Defendant’s Memorandum of Points and Authorities in Support of Its Motion for Summary Judgment on the Issue of Causation, Daubert v. Merrell Dow Pharms., Inc., Case No. 84-2013-G(I) (S.D. Cal. Aug. 2, 1989). The motion was made in a companion case before Judge Gilliam as well, Schuller v. Merrell Dow Pharms., Inc., Case No. 84-2929-G(I). The first Daubert motion may not have been the first one drafted. The linked brief is the first one as filed.

[2] See Oxendine v. Merrell Dow Pharms., Inc., 563 A.2d 330 (D.C. Ct. App. 1989).

[3] William Griffith McBride, Thalidomide and Congenital Abnormalities, 278 LANCET 1358 (1961).

[4] William Griffith McBride, McBride criticizes inquiry, 336 NATURE 614 (1988); Norman Swan, Disciplinary tribunal for McBride, 299 BRIT. MED. J. 1360 (1989); G. F. Humphrey, Scientific fraud: the McBride case, 32 MED. SCI. LAW 199 (1992); Mark Lawson, McBride found guilty of fraud, 361 NATURE 673 (1993); Leigh Dayton, Thalidomide hero found guilty of scientific fraud, NEW SCI. (Feb.27, 1993); William McBride: alerted the world to the dangers of thalidomide in fetal development, 362 BRIT. MED. J. k3415 (2018).

[5] McBride v. Merrell Dow & Pharms., Inc., 800 F.2d 1208 (D.C. Ct. App. 1986). McBride ultimately failed against all his litigation targets.

[6] See In Re Richardson-Merrell. Inc. Bendectin Prods. Liab. Litig., 624 F.Supp. 1212 (S.D. Ohio 1985); aff’d sub nom. In re Bendectin Litig., 857 F.2d 290 (6th Cir. 1988); cert. denied, 488 US 1006 (1989).

[7] Brock v. Merrell Dow Pharmaceuticals Inc., 874 F.2d 307 (5th Cir. 1989); Richardson y. Richardson-Merrell, 857 F.2d 823 (D.C. Cir. 1988); Lynch v. Merrell-National Labs., 830 F.2d 1190 (1st Cir. 1987) (affirming grant of summary judgment).

[8] US Food & Drug Admin., Determination That Bendectin Was Not Withdrawn from Sale for Reasons of Safety or Effectiveness, 64 FED. REG. 43190–1 (1999).

[9] Brief at 3-4.

[10] Barry Nace was one of the lead plaintiffs’ counsel in the Bendectin litigation, and he represented the Daubert family. Nace was also formerly President of the lawsuit industry’s principal lobbying organization, the American Trial Lawyers Association (now the AAJ). See also In re Barry J. Nace, A Member of the Bar of the District of Columbia Court of Appeals (Bar Registration No. 130724), No. 13–BG–1439, Slip op. (Sept. 4, 2014), available at <https://www.dccourts.gov/sites/default/files/pdf-opinions/13-BG-1439.pdf>, last visited on Feb. 8, 2026.

[11] See Michael D. Green, Pessimism about Milward, 3 WAKE FOREST J. L & POL’Y 41, 63 (2013) (paraphrasing Nace as describing the mosaic theory as “[d]amn brilliant, and I was the one who thought of it and fed it to Alan [Done].”).

[12] Id. at 61 (2013) (citing Oxendine v. Merrell Dow Pharm., Inc., 506 A.2d 1100, 1110 (D.C. 1986).

[13] Harry Frankfurt, ON BULLSHIT 63 (2005).

[14] In re “Agent Orange” Prod. Liab. Litig., 611 F. Supp. 1223 (E.D.N.Y. 1985), aff’d, 818 F.2d 187 (2d Cir. 1987), cert. denied, 487 U.S. 1234 (1988).

[15] Id. at p. 1231.

[16] United States Dep’t of Justice, Tort Policy Working Group, Report of the Tort Policy Working Group on the causes, extent and policy implications of the current crisis in insurance availability and affordability at 35 (Report No. 027-000-01251-5) (Wash. DC 1986), available at https://archive.org/details/micro_IA41152903_0369.

[17] In Re Air Crash Disaster at New Orleans, 795 F.2d 1230, 1233-34 (5th Cir. 1986).

[18] Id. at 1233-34.

[19] The Brief, at 2, cited United States v. Kilgus, 571 F.2d 508, 510 (9th Cir. 1987) (citing Frye).

[20] An Act to Establish Rules of Evidence for Certain Courts and Proceedings. Pub. L. 93–595, 88 Stat. 1926 (1975).

[21] Brief at 17.

[22] 545 F.Supp. 306, 308 (N.D. Cal. 1982). See generally Richard E. Neustadt & Harvey V. Fineberg, THE SWINE FLU AFFAIR: DECISION-MAKING ON A SLIPPERY DISEASE (Nat’l Acad. Sci. 1978).

[23] Daubert v. Merrell Dow Pharms., Inc., 727 F.Supp. 570 (S.D. Cal. 1989).

[24] Id. at 571, citing United States v. Kilgus, 571 F.2d 508, 510 (9th Cir.1978).

[25] Id. at 572 (citing Brock, 874 F.2d at 310).

[26] Id. at 574. The use of “association” was at best ambiguous, because it begged the question whether it as an association that was “clear cut” (reasonably free from bias and confounding), and beyond that which we would care to attribute to chance.

[27] Daubert v. Merrell Dow Pharms., Inc., 951 F.2d 1128 (9th Cir. 1991).

[28] Brock v. Merrell Dow Pharms., Inc., 874 F.2d 307, modified, 884 F.2d 166 (5th Cir.1989), cert. denied, 494 U.S. 1046 (1990); Richardson v. Richardson–Merrell, Inc., 857 F.2d 823 (D.C.Cir.1988), cert. denied, 493 U.S. 882 (1989); Lynch v. Merrell–National Labs., 830 F.2d 1190 (1st Cir.1987).

[29] DeLuca v. Merrell Dow Pharmaceuticals, Inc., 131 F.R.D. 71 (D.N.J.) (granting summary judgment), rev’d and remanded, 911 F.2d 941 (3d Cir.1990). On remand, the district court entered summary judgment on the alternative reasoning of Rule 702, as interpreted by the Third Circuit. DeLuca v. Merrell Dow Pharms., Inc., 791 F.Supp. 1042, 1048 (D.N.J. 1992) (re-entering summary judgment after considering Rule 702), aff’d, 6 F.3d 778 (3d Cir.1993) (per curiam), cert. denied, 510 U.S. 1044 (1994).

[30] Daubert v. Merrell Dow Pharms., Inc., 951 F.2d 1128, 1131 (9th Cir. 1991).

[31] Lynch v. Merrell–National Labs., 830 F.2d 1190, 1194-95 (1st Cir.1987).

[32] Paul M. McKeigue, Steven H. Lamm, Shai Linn & Jeffrey S. Kutcher, Bendectin and Birth Defects: I. A Meta-Analysis of the Epidemiologic Studies, 50 TERATOLOGY 27 (1994). This meta-analysis made no correction for multiple comparisons in examining many different types of birth defects.

Posted in Causation, Expert Witnesses, Frye, Meta-analysis, Peer Review, Rule 702, Rule 703, Scientific Evidence | No Comments »

Prada – Fashionable, But Unreliable Review on Acetaminophen and Autism

September 30th, 2025

Back in the first week of this month, I posted about a paper (Prada 2025),[1]  which featured a so-called navigation-guide systematic review of the scientific evidence on the issue whether pregnant women’s ingestion of acetaminophen causes their children to develop autism.[2] The focus of my post was on some dodgy aspects of the Prada review, such as its anemic disclosures of interest, and its squirrely claim to have been “NIH funded.”

Since posting, the Prada review has been very much in the news. Last week, President Trump held a news conference, where we learned that he cannot pronounce acetaminophen and that he has a strongly held opinion that acetaminophen causes autism.[3] Trump was surrounded by officials in his administration, including plaintiffs’ lawyer Robert Kennedy, Jr., and three physicians, Drs. Oz, Makary, and Bhattacharya, who looked on in apparent approval. Once upon a time, a risk communication such as this one about acetaminophen, would have come out from a non-political FDA employee, such as Janet Woodcock, who was head of Drug Safety, and for many years the Director of Center for Drug Evaluation and Research. Over her tenure, Dr. Woodcock weighed in on many pharmaceutical safety issues. Those of us who have been involved in litigation of those safety issues remember that Dr. Woodcock chose her language very carefully. She did not just give opinions; she marshalled facts.

Admittedly, Trump’s autism press conference was not as deranged as his 2020 press conference at which he suggested that injecting sodium hypochlorite (bleach) into patients would cure Covid-19 infections. Still, most of the world was left with the impression that Trump was replacing (DOGE-ing) scientific research and replacing it with irrational speculation. Trump’s press conference on acetaminophen and vaccines was widely met with skepticism and disbelief. Medical ethicist Dr. Arthur Caplan, who is not given to hyperbole, called the conference “the saddest display of a lack of evidence, rumors, recycling old myths, lousy advice, outright lies, and dangerous advice I have ever witnessed by anyone in authority.”[4]

When the administration physicians communicated with the public, they said something very different from Trump’s presentation. In her press release, Press Secretary Karoline Leavitt used the meaningless locution, “suggested link,” and cited the Prada review, which eschewed causal conclusions:[5]

“Andrea Baccarelli, M.D., Ph.D., Dean of the Faculty, Harvard T.H. Chan School of Public Health: “Colleagues and I recently conducted a rigorous review, funded by a grant from the National Institutes of Health (NIH), of the potential risks of acetaminophen use during pregnancy… We found evidence of an association between exposure to acetaminophen during pregnancy and increased incidence of neurodevelopmental disorders in children.

Harvard University: Using acetaminophen during pregnancy may increase children’s autism and ADHD risk.”

Of course, saying that something “may increase risk” is not even close to saying that something causes the outcome in question. And Baccarelli’s description of his paper, Prada review, as funded by the National Institutes of Health is misleading at best.[6]

Leavitt went on to declare that “[t]he Trump Administration does not believe popping more pills is always the answer for better health.” Unless of course, it is Propecia for Mr. Trump, testosterone for Mr. Kennedy, or ketamine for Mr. Musk.

FDA Commissioner Martin A. Makary issued a Notice, the same day, in which he declared:

“In recent years, evidence has accumulated suggesting that the use of acetaminophen by pregnant women may be associated with an increased risk of neurological conditions such as autism and ADHD in children.

* * *

To be clear, while an association between acetaminophen and autism has been described in many studies, a causal relationship has not been established and there are contrary studies in the scientific literature.”[7]

So the FDA is clearly not declaring that acetaminophen causes autism.

Dr. Mehmet Oz, former surgeon and television talking head, who stood mute by Trump’s side at the infamous press conference, found his voice later in the week, when he acknowledged that pregnant women of course should take acetaminophen when physicians direct them to do so.

In Europe, where pharmaceutical regulation is typically more precautionary than in the United States, both the European Medicines Agency and the U.K.’s Medicines and Healthcare Products Regulatory Agency announced that using acetaminophen during pregnancy was safe with no showing that it causes autism in offspring.[8] Steffen Thirstrup, the EMA’s Chief Medical Officer, announced a day after the Trump bungle, that:

“Paracetamol [acetaminophen] remains an important option to treat pain or fever in pregnant women. Our advice is based on a rigorous assessment of the available scientific data and we have found no evidence that taking paracetamol during pregnancy causes autism in children.”

Most medical organizations were appalled at the administration’s sloppy messaging. The day after the press conference, the American College of Medical Toxicology (ACMT) issued a statement in response, to affirm the safety of acetaminophen in pregnancy.[9] The ACMT noted that its position was in agreement with the American College of Obstetrics and Gynecologists, the Society for Maternal-Fetal Medicine, the American Academy of Pediatrics, and the Society for Developmental and Behavioral Pediatrics.

The acetaminophen kerfuffle seems always to come back to the Prada “navigation guide” systematic review and its authors, including the Harvard Dean, Andrea Baccarelli, who was the well-paid member of the plaintiffs’ expert witness team in acetaminophen litigation.[10] Why did Dr. Andrea Baccarelli in the Prada review use this curious, arcane, and infrequently used method of review? Why did Baccarelli and his co-authors publish this review in Environmental Health, which is dedicated to publishing “manuscripts on important aspects of environmental and occupational medicine,” which places maternal ingestion of a licensed pharmaceutical outside its stated competence? Why did Baccarelli offer a litigation opinion that acetaminophen causes autism, but retreat to “association” when writing for the scientific community? And why did Baccarelli and his co-authors not disclose that Baccarelli had submitted essentially the same navigation guide systematic review as his proffered expert witness testimony, and that a federal court had rejected his opinion as not “the product of reliable principles and methods,” and not “a reliable application of the principles and methods to the facts of the case”[11]? Perhaps the answers are obvious to most observers, but candid disclosures certainly would have provided important context, and saved some people the embarrassment of relying upon the Prada review.

In digging deeper into the history of the navigation guide method itself, the earliest citation I could find to such systematic reviews was in 2009, in a conference paper that discussed this approach as a proposal.[12] The authors that made up the Navigating the Scientific Evidence to Improve Prevention Workshop Organizing Committee were not particularly well known or distinguished in the field of research synthesis. Still, there must be other reasons that “navigation guide” reviews are not more prevalent if the Organizing Committee had been truly on to something important.

The Committee never identified a rationale for a new systematic review approach. When the Organizing Committee outlined its approach in 2009, there were well over three decades of experience with systematic reviews,[13] with well-regarded full-length textbook treatment by experts in the field.[14]

In addition to the lack of experience among its authors and the preemption of the subject by comprehensive treatments elsewhere, there were three additional curious take aways from a cursory reading of the Organizing Committee’s 2009 manuscript. First, Committee emphasized the alleged need for a review methodology for environmental exposures. This emphasis was never accompanied by a showing that well-described methodologies long in use were somehow inadequate or inappropriate for environmental exposures.

Second, the authors urged the need for precautionary assessments, which might make their method fine where syntheses for precautionary pronouncements were called for. In the United States, regulatory assessments vary depending up the governing statutes that create the regulatory mandate.  In personal injury litigation, the precautionary principle is nothing less than an end run around the burden of proof on the party claiming harm and suing in tort. The designated subject matter of environmental exposures for the proposed systematic review technique offers an insight into why these authors believed that they had to propose a new fangled systematic review methodology. Previously described methods interfered with authors’ ability to elevate “iffy” associations into conclusions of causality in the name of the precautionary principle.

The third curiosity in the 2009 manuscript is that the authors never described the need for a pre-specified protocol. Later articles on this proposed methodology similarly failed to describe the need for such a protocol,[15] although by 2014, authors from the original Organizing Committee reversed course to add a pre-specified protocol to the requirements for a navigation guide systematic review.[16]

A recent article defines a systematic review essentially in terms of a protocol:

“Systematic review (SR) is a rigorous, protocol-driven approach designed to minimise error and bias when summarising the body of research evidence relevant to a specific scientific question.”[17]

The purpose of a protocol may be obvious to anyone who has been paying attention to the replication crisis in biomedical literature, but the same article offers a helpful description of its rationale:

“The purposes of the protocol are to discourage ad-hoc changes to methodology during the review process which may introduce bias, to allow any justifiable methodological changes to be tracked, and also to allow peer-review of the work that it is proposed, to help ensure the utility and validity of its objectives and methods.”[18]

Systematic reviews vary widely in quality, methodological rigor, and validity, but one of the key determinants of their validity is whether they were preceded by pre-specified protocol. Although systematic reviews are often described the “gold standard” for evidence synthesis, their methodological rigor vary widely. Reviews that lack a pre-specified protocol are decidedly less rigorous than those reviews that employ a protocol.[19] The absence of a protocol is thus an important tell that a systematic review may be untrustworthy.

The Prada paper put together by Baccarelli’s team has no protocol. It may satisfy the Trump administration’s Fool’s Gold Standard for Science, but that is far short of the requirements of Federal Rule of Evidence 702. Given Baccarelli’s abridgement of scientific method, we should not be overly surprised by Judge Cote’s judgment of the failures of Baccarelli’s and the other plaintiffs’ expert witnesses’ proffered opinions in the acetaminophen litigation:

“their analyses have not served to enlighten but to obfuscate the weakness of the evidence on which they purport to rely and the contradictions in the research. As performed by the plaintiffs’ experts, their transdiagnostic analysis has obscured instead of informing the inquiry on causation.”[20]

Judge Cote carefully reviewed Baccarelli’s proffered testimony and found it replete with cursory analyses, cherry-picked data, and result-driven assessments of studies.[21] Her Honor’s findings would seem to apply with equal measure to the Prada review.

[1] Diddier Prada, Beate Ritz, Ann Z. Bauer and Andrea A. Baccarelli, “Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology,” 24 Envt’l Health 56 (2025).

[2] See Schachtman, “Acetaminophen & Autism – Prada Review Misleadingly Claims to Be NIH Funded,” Tortini (Sept. 9, 2025).

[3] Jeff Mason, Ahmed Aboulenein, and Julie Steenhuysen, “Trump Links Autism to Tylenol and Vaccines, Claims Not Backed by Science,” Reuters (Sept. 22, 2025); Brianna Abbott & Andrea Petersen, “The Trump administration said acetaminophen could cause autism. Doctors maintain it is safe during pregnancy,” Wall St. J. (Sept. 22, 2025) (“Studies looking at a link [sic] between acetaminophen and autism are inconclusive.”); Will Weissert, “Dr. Trump? The president reprises his COVID era, this time sharing unproven medical advice on autism,” Wash. Post (Sept. 23, 2025).

[4] Ali Swenson & Lauran Neergaard, “Trump makes unfounded claims about Tylenol and repeats discredited link between vaccines and autism,” Assoc. Press (Sept. 23, 2025).

[5] Leavitt, “FACT: Evidence Suggests Link Between Acetaminophen, Autism,” The White House (Sept. 22, 2025).

[6] See Schachtman, “Acetaminophen & Autism – Prada Review Misleadingly Claims to Be NIH Funded,” Tortini (Sept. 9, 2025). The referenced grants had nothing to do with acetaminophen and autism, or even autism generally. The NIEHS granted Dr. Baccarelli money to study air pollution and brain aging. The exposure of interest was not acetaminophen, and the outcome of interest was not autism. By claiming that his research was “NIH funded,” Baccarelli was attempting to boost the prestige of the research even though his acetaminophen review was done for litigation, not for the federal government. Apparently the NIEHS acquiesces in this charade because it suggests to the uninitiated that its research grants result in more published papers, even though the topics of those papers are unrelated to the funded research proposal, and the unrelated topics never receiving committee peer review.

[7] Martin A. Makary, “Notice to Physicians on the Use of Acetaminophen During Pregnancy,” (Sept. 22, 2025).

[8] E.M.A., “Use of paracetamol during pregnancy unchanged in the EU,” (Sept. 23, 2025).

[9] ACMT Supports the Safe Use of Acetaminophen in Pregnancy (Sept. 23, 2025).

[10] Rebecca Robbins & Azeen Ghorayshi, “Harvard Dean Was Paid $150,000 as an Expert Witness in Tylenol Lawsuits,” N.Y. Times (Sept. 23, 2025).

[11] Fed. R. Evid. 702.

[12] Patrice Sutton, Heather Sarantis, Julia Quint, Mark Miller, Michele Ondeck, Rivka Gordon, and Tracey Woodruff, “Navigating the Scientific Evidence to Improve Prevention: A Proposal to Develop A Transparent and Systematic Methodology to Sort the Scientific Evidence Linking Environmental Exposures to Reproductive Health Outcomes,”  (July 29, 2009).

[13] See Quan Nha Hong & Pierre Pluye, “Systematic reviews: A brief historical overview,” 34 Education for Information 261, 261 (2018) (describing the evolution of systematic reviews as made up of a “foundation period 1970-1989,” an “institutionalization period 1990-2000, and a “diversification period” from 2001 forward.)

[14] Matthias Egger, Julian P. T. Higgins, and George Davey Smith, Systematic Reviews in Health Research: Meta-Analysis in Context (3rd ed. 2022). The first edition of this text was published in 1995.

[15] Tracey J. Woodruff, Patrice Sutton, and The Navigation Guide Work Group, “An Evidence-Based Medicine Methodology To Bridge The Gap Between Clinical And Environmental Health Sciences,” 30 Health Affairs 931 (2011); Julia R. Barrett, “The Navigation Guide Systematic Review for the Environmental Health Sciences,” 122 Envt’l Health Persp. A283 (2014).

[16] Tracey J. Woodruff & Patrice Sutton, “The Navigation Guide Systematic Review Methodology: A Rigorous and Transparent Method for Translating Environmental Health Science into Better Health Outcomes,” 122 Environ Health Perspect. 1007 (2014).

[17] Paul Whaley, Crispin Halsall, Marlene Ågerstrand, Elisa Aiassa, Diane Benford, Gary Bilotta, David Coggon, Chris Collins, Ciara Dempsey, Raquel Duarte-Davidson, Rex Fitzgerald, Malyka Galay-Burgos, David Gee, Sebastian Hoffmann, Juleen Lam, Toby Lasserson, Len Levy, Steven Lipworth, Sarah Mackenzie Ross, Olwenn Martin, Catherine Meads, Monika Meyer-Baron, James Miller, Camilla Pease, Andrew Rooney, Alison Sapiets, Gavin Stewart, and David Taylor, “Implementing systematic review techniques in chemical risk assessment: Challenges, opportunities and recommendations,” 92-93 Env’t Internat’l 556 (2016).

[18] Id. at 560.

[19] Julia Menon, Fréderique Struijs & Paul Whaley, “The methodological rigour of systematic reviews in environmental health,” 52 Critical Rev Toxicol. 167 (2022).

[20] In re Acetaminophen ASD-ADHD Prods. Liab. Litig., 707 F. Supp. 3d 309, 334, 2023 WL 8711617 (S.D.N.Y. 2023) (Cote, J.).

[21] Id. at 354-56.

Posted in Causation, Expert Witness Hall of Shame, Rule 702, Scientific Evidence | No Comments »

Acetaminophen & Autism – Prada Review Misleadingly Claims to Be NIH Funded

September 9th, 2025

A few weeks ago, four scientists published what they called a “navigation guide” systematic review on acetaminophen use and autism.[1] The last named author, Andrea A. Baccarelli, is an environmental epidemiologist, who has been an expert witness for plaintiffs’ counsel in lawsuits against the manufacturers and sellers of acetaminophen. Another author, Beate Ritz, frequently testifies for the lawsuit industry in cases against various manufacturing industries. A third author, Ann Z. Bauer, was the lead author of a [faux] “consensus statement” that invoked the precautionary principle to call for limits on the use of acetaminophen (N-acetyl-p-aminophenol or APAP) by pregnant women, on grounds that such use may increase the risks of neurodevelopmental (including autism), reproductive and urogenital disorders.[2] The lead author was Diddier Prada, who works in Manhattan, at the Icahn School of Medicine at Mount Sinai, in the environmental and climate science department, within the Institute for Health Equity Research. The Mount Sinai website describes Dr. Diddier Prada as an environmental and molecular epidemiologist who focuses on the role of environmental toxicants in age-related conditions

Curious readers might wonder how someone whose interest is in environmental issues and “health equity” became involved in a review of pharmaco-epidemiology and teratology. The flavor of systematic review deployed in the paper, “navigation guide,” originated and has had limited use in the field of environmental issues. To my knowledge, so-called navigation guides have never been used previously in pharmaco-epidemiologic or teratologic controversies.[3]

The Prada paper and its deployment of a “navigation guide” systematic review deserve greater critical scrutiny.  In this post, however, I want to address some peripheral issues, such as “competing interests” and misleading claims about the paper’s having been NIH funded.

Only Dr. Baccarelli disclosed a potential conflict of interest, in a statement that many would judge to be anemic:

“Dr. Baccarelli served as an expert witness for the plaintiff’s legal team on matters of general causation involving acetaminophen use during pregnancy and its potential links to neurodevelopmental disorders. This involvement may be perceived as a conflict of interest regarding the information presented in this paper on acetaminophen and neurodevelopmental outcomes. Dr. Baccarelli has made every effort to ensure that this current work—like his past work as an expert witness on this matter—was conducted with the highest standards of scientific integrity and objectivity.”

The disclosure fails to mention whether Dr. Baccarelli was compensated for his playing on the “plaintiff’s legal team,” and if so, then how much. Using the passive voice, he suggests that this work might be perceived as a conflict of interest, when surely he knows that it is a serious issue. If industry scientists working on the relevant issue had published, they surely would be accused of having had a conflict.

Dr. Baccarelli self-servingly, falsely, and with epistemic arrogance, asserts that he made every effort in this paper, and in his past work as an expert witness, to conform to the “highest standards of scientific integrity and objectivity.” Despite his best efforts to be “scientific,” Baccarelli’s work failed critical scrutiny in the multi-district litigation that consolidated acetaminophen cases for pre-trial handling. In that litigation, the defense challenged Dr. Baccarelli’s opinions under Rule 702, for their lack of validity. In an extensive, closely reasoned opinion, federal district court judge Denise Cote ruled that Dr. Baccarelli’s proffered opinions failed to meet the relevance and reliability standards of federal law.[4]

The MDL court easily found that Dr. Baccarelli was qualified to provide an opinion on epidemiology, although the focus of his career has been on environmental issues. Baccarelli’s substantive problem was that he deviated from accepted and valid methods of causal inference by cherry picking different results and outcomes across multiple studies. Baccarelli’s sophistical trick was to advance a “transdiagnostic” analysis that lumps an already heterogenous autism spectrum disorder (ASD), with attention-deficit hyperactivity disorder (ADHD), and a grab bag of “other neurodevelopmental disorders.” If a study found a putative association with only one of the three end points, Baccarelli would claim success on all three. Baccarelli avoided conducting separate ASD and ADHD analyses, and he cherry picked the end points that supported his pre-determined conclusions.

Judge Cote found that the transdiagnostic analyses advanced by plaintiffs’ expert witnesses, including Baccarelli, obscured and obfuscated more than they informed the causal inquiry.[5] The court’s analysis casts considerable shade upon Baccarelli’s self-serving claim to have used “the highest standards of scientific integrity and objectivity.” Judge Cote barred Baccarelli and the other members of the plaintiffs’ “expert team” from testifying.

Conspicuously absent from the conflict disclosure section of the Prada article was any mention of the litigation work of co-author Beate Ritz. In 2007, Ritz became a fellow of the Collegium Ramazzini, which functions in support of the lawsuit industry much as the scientists of the Tobacco Institute supported tobacco legal defense efforts in times past. Ritz’s fellowship in the Collegium makes her a full-fledged member of the Lobby and a supporter of the lawsuit industry.[6] Ritz has testified, for claimants, in cases involving claims of heavy metals in baby food, in cases involving claims that paraquat exposure caused Parkinson’s disease, and most notoriously for plaintiffs in glyphosate litigation, where her witnessing is often done for the Wisner Baum lawfirm that employs the son of Robert F. Kennedy, Jr.[7]

The conflict of interest disclosure statement is hardly the only misleading aspect of the Prada paper. At the end of the paper, the authors state, with respect to funding that their “study was supported by NIH (R35ES031688; U54CA267776).” Some people may incorrectly believe that the Prada review was directly sponsored and funded by the National Institutes of Health.  Nothing could be further from the truth.

The research grant referenced, R35ES031688, is a National Institute of Environmental Health Sciences (NIEHS) research grant. The curious reader might inquire what whether and why the NIEHS would be concerned about a pharmacological issue. The short answer is that the NIEHS is not, and that this grant has nothing to do with children’s neurological status in relation to their mother’s ingestion of acetaminophen.

The NIEHS award this research grant to Andrea Baccarelli, while he was at Columbia University, for his project “Extracellular Vesicles in Environmental Epidemiology Studies of Aging.” The research focuses on extracellular vesicles (EVs) and their role in environmental health, particularly as it relates to aging. What Baccarelli promised to do with this NIEHS grant was to study the effects of air pollution on accelerated brain aging, and disease states such as dementia. Baccarelli noted that his focus would be on intra-cellular communication enabled by extracellular vesicles, in reaction to air pollution. The described research would understandably be viewed as potentially relevant to the NIEHS mission statement, but it has nothing to do with autism among children of women who ingested acetaminophen during pregnancy.  The phrases “extracellular vesicles” and “air pollution” do not appear in the Prada review.

The second grant listed under funding for the Prada review was U54CA267776. The U54 designation marks this as a career award, not specific to a specific topic or this published work. Ironically, the grant is a diversity, equity, and inclusion grant to the Mount Sinai Icahn School of Medicine, in Manhattan. The Icahn School has long had one of the most ethically, racially, culturally diverse faculties of any medical school, and hardly needs financial incentives to hire minority physicians and scientists.

The NIH awarded grant U54CA267776 for “Cohort Cluster Hiring Initiative at Icahn School of Medicine at Mount Sinai.” The NIH describes the grant as aiming to reduce “[t]he barriers to research and career success for underrepresented groups in academic medicine.” The text of the U54 grant is written largely in bureaucratic jargon, which may require a degree in DEI to understand fully. What is abundantly clear is that nothing in this U54 grant, or in its stated criteria for evaluation, has anything to do with studying the teratologic potential of acetaminophen.

What so far has escaped the media’s attention is that Prada and colleagues did not have NIH (or NIEHS) support for their acetaminophen review. They had career-level support for DEI purposes, or perhaps general “walking-around” money for research on environmental pollution and brain aging, which has nothing to do with the subject of their navigation guide review. The authors of the Prada review never prepared a study proposal related to acetaminophen for evaluation by a funding committee at NIH. The authors never submitted a protocol to the NIH, and the NIH provided no peer review or guidance for the authors’ acetaminophen review. In short, there is nothing that marks the Prada review as an NIH work product other than the over-claiming of the authors with respect to funding sources.

The Prada review has attracted a lot of attention in the media and from the worm-brained Secretary of Health and Human Services. An article in the Washington Post described the Prada review as NIH funded, which tracks the paper’s misleading disclosure.[8] The media no doubt jumped on the publication of the Prada review last month because Secretary Kennedy promised to reveal the cause of autism by September. We can imagine that Kennedy will be tempted to embrace the Prada review because he can falsely mischaracterize it as an NIH-funded review.

Not only is the funding claim dodgy, but so is the suggestion that the review supports a conclusion of causation between maternal ingestion of acetaminophen and autism in children. The lead author, Dr. Diddier Prada, noted the frequent confusion between correlation and causation and explicitly stated the authors of the review “cannot answer the question about causation.”[9]

[1] Diddier Prada, Beate Ritz, Ann Z. Bauer and Andrea A. Baccarelli, “Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology,” 24 Envt’l Health 56 (2025).

[2] Ann Z. Bauer et al., “Paracetamol Use During Pregnancy — A Call for Precautionary Action,” 17 Nature Rev. Endocrinology 757 (2021).

[3] See Tracey J. Woodruff, Patrice Sutton, and The Navigation Guide Work Group, “An Evidence-Based Medicine Methodology To Bridge The Gap Between Clinical And Environmental Health Sciences,” 30 Health Affairs 931 (May 2011).

[4] In re Acetaminophen ASD-ADHD Prods. Liab. Litig., 707 F. Supp. 3d 309, 2023 WL 8711617 (S.D.N.Y. 2023) (Cote, J.).

[5] Id. at 334.

[6] See F.D.K. Liddell, “Magic, Menace, Myth and Malice,” 41 Ann. Occup. Hyg. 3, 3 (1997).

[7] See, e.g., In re Roundup Prods. Liab. Litig., 390 F. Supp. 3d 1102 (2018); Barrera v. Monsanto Co., Del. Super. Ct. (May 31, 2019); Pilliod v. Monsanto Co., 67 Cal. App. 5th 591, 282 Cal. Rptr. 3d 679 (2021). See also Dan Charles, “Taking the stand: For scientists, going to court as an expert witness brings risks and rewards,” 383 Science 942 (Feb. 29, 2024) (quoting Ritz as suggesting that she was reluctant to get involved as an expert witnesses).

[8] Ariana Eunjung Cha, Caitlin Gilbert and Lauren Weber, “MAHA activists have been pushing for more investigation into use of the common pain killer during pregnancy,” Wash. Post (Sept. 5, 2025). See also Liz Essley Whyte & Nidhi Subbaraman, “RFK Jr., HHS to Link Autism to Tylenol Use in Pregnancy and Folate Deficiencies,” Wall St. J. (Sept. 5, 2025).

[9] Jess Steier, “Saturday Morning Thoughts on the Tylenol-Autism News: The public health whiplash continues as we play another round of ‘autism cause’ roulette,” Unbiased Science (substack) (Sept. 06, 2025).

Posted in Causation, Conflicts of Interest, Expert Witnesses, Rule 702, Scientific Evidence | 2 Comments »

AAAS Conference on Scientific Evidence and the Courts

September 8th, 2025

Back in September 2023, the American Association for the Advancement of Science (AAAS), with its Center for Scientific Responsibility and Justice, sponsored a two day meeting on Scientific Evidence and the Courts. If there were notices for this conference, I missed them. The meeting presentations are now available online. Judging from camera views of the audience, the conference did not appear to be well attended. Most of the material was forgettable, but some of the presentations are worth watching.

Jennifer L. Mnookin opened the conference with a keynote presentation on “Where Law and Science Meet.” Chancellor Mnookin presented a broad overview and some interesting insights on the development of the evidence law of expert witness testimony.

Following Mnookin, Professors Ronald Allen and Andrew Jurs presented on the “Unintended Impacts [sic] of the Daubert Standard.” The conference took place only a few months before amendment to Rule 702 became effective, and the reference to a “Daubert” standard was untoward. Allen’s comments followed the path of his previous articles. Jurs presented some empirical legal research, which seemed flawed for its assumption that the Frye standard was universally applied in federal court before the advent of Daubert. Assessing whether these standards lead to different outcomes when both standards have been applied heterogeneously, and one standard, Frye, is often not applied at all, and Daubert is often flyblown by judges hostile to the gatekeeping enterprise, Jurs’ empirical research seemed both invalid and very much beside the point. Both presenters missed the key point of Daubert, in which case plaintiff’s counsel advocated for no standard at all, beyond basic subject-matter qualification, for giving expert opinions in court.

A Session on “An International Perspective,” Scott Carlson discussed the efforts of the American Bar Association (ABA), and its Center of Global Programs, on supporting judges in foreign countries. Prateek Sibal discussed the history and work of the UNESCO Global Judges Initiative. My sincere wish is that the ABA would support judges more in the United States.

Panelists Valerie P. Hans, Emily Murphy, and Dr. Michael J. Saks presented on various jury issues, in a session “In the Minds of the Jury.” The presentations on how foreign countries process expert witness testimony were lacking any mention of how juries rarely if ever sit in civil cases that involve complex technical and scientific issues.

Two editors of scientific journals, Adriana Bankston and Valda Vinson, along with law professor Michael Sakes, spoke about peer review and publication, in  a session “As a Matter of Fact: ‘General Acceptance’ in Emerging vs. Established Science.” Their discussion on the publication process shed very little light on how courts and juries should assess the validity of specific papers, particularly in view of the lax practices at many journals. Towards the end of this session, a question from the audience proved to be very revealing of the prejudices of the law professor on the panel. The questioner rose to complain that after beginning research on a topic that has litigation relevance her research is now frequently questioned. She asked the panel how she might deal with the annoyance of being questioned. Some on the panel basically urged her to buck up, but the law professor invoked the spirit of agnothologist, and lawsuit industry expert witness, David Michael, to suggest that “manufacturing doubt” was just a corporate tactic in the face of scientific evidence. The prejudice against corporate speech is remarkable when the lawsuit industry has a long history of playing the ad hominem game in advancing its pecuniary interests.

The session that followed addressed how trustworthy science might best be put before courts. The organizers described this session, Utilizing Scientific and Technical Expertise, as going to the heart of the issues targeted by the conference. Joe S. Cecil, Deanne M. Ottaviano, and Shari Seidman Diamond discussed how scientific expertise enters into the evidentiary record in American courtrooms. Their presentations were interesting, but curiously no one mentioned that the primary avenue for expert witness opinion is through oral testimony!

Joe Cecil discussed methods judges have to obtain scientific and technical evidence to advance justice. (By this I hope he meant the truth, and not just the outcome preferred by social justice warriors.) As noted, Joe Cecil did not focus on the ordinary methods of direct and cross-examination of party expert witnesses, but rather, he identified other methods of introducing expertise into the courtroom for the benefit of the judge or the jury. Only one suggestion really affects jury comprehension, namely the appointment of non-party expert witnesses by the court. The other methods really only provide expertise to the trial judge, who perhaps is challenged to make a ruling under Federal Rule of Evidence 702. The federal courts have the inherent supervisory power to appoint technical advisors to act as special law clerks on issues. Similarly, appointed special masters can address technical implementation issues, subject to the district judges’ control. The judges are always free to read outside the briefs and testimony, but there are ethical and notice issues for such conduct. The Reference Manual on Scientific Evidence (RMSE) sits on the shelves on every federal judge’s bookshelf, even if in pristine, unused condition. Judges can at least read the RMSE on specific issues without having to disclose their extra-curricular research to the parties.  Of course, parties are well advised to consider any materials in the RMSE, which support or oppose their contentions.

In discussing the RMSE, Cecil noted that the fourth edition was in the works. He also mentioned that all the old chapter topics would be carried forward to the fourth edition, and that new topics would include eyewitness identification, computer science, artificial intelligence, and climate science. Sadly, there will be no chapter on genetic determination of disease, but perhaps the clinical medicine chapter will take on the subject in greater detail than previous editions. This conference took place two years ago, and yet the RMSE, fourth edition, is still not published. The National Academies website previously listed the project as completed, but the site now describes the work as “in progress.”

Joe Cecil’s analysis of the various extraordinary expert techniques was pretty much spot on, especially his assessment that “experiments” with court-appointed experts were often failures or at best modest successes. The discussion of Judge Pointer’s Rule 706 independent expert witnesses in the silicon [sic] breast implant litigation, MDL926, seemed to lack context. Cecil acknowledged that the court’s expert witnesses contributed some value to admissibility decisions, but Judge Pointer notoriously did not believe that he, as the MDL judge, had any responsibility for Rule 702 determinations, and he made none except in cases that he tried in the Northern District of Alabama. (And these decisions were before the Science Panel was appointed.) So the Rule 706 witnesses really could not have aided in admissibility decisions.

The real value – in my view – of the Science Panel was that it demonstrated that Judge Pointer was quite wrong in believing that both sides’ expert witnesses were simply “too extreme,” or too partisan, and that the truth was somehow in the middle. Indeed, Judge Pointer said so on many occasions, and he was judicially gobsmacked when all four of his experts roundly rejected the plaintiffs’ distortions of the science of immunology, epidemiology, toxicology, and rheumatology. The courts’ expert witnesses sat for discovery depositions, and then gave testimony de bene esse. To my knowledge, their testimony was never admitted in any of the subsequent trials.

Judge Jed Rakoff gave an interesting presentation, “Strengthening Cooperation Between the Scientific Enterprise and the Justice System,” on the intersection between scientific and legal expertise and the need for their better integration. Judge Rakoff focused on the astonishing lack of compliance of trial judges with the gatekeeping requirements of Rule 702 in addressing the admissibility of forensic evidence. Several subsequent panels also addressed forensic topics, including “A Texas Case Study in Accountability for Forensic Sciences,” “Innovations in Investigative Technologies Improvements and Drawbacks,” and “Artificial Intelligence and the Courts,” “Wrongful Convictions and Changed Science: Statutes,” and “Standing Up for Justice: When the Law and Science Work Hand-in-Hand.”

One of the more curious sessions was on “Statistical Modeling and Causation Science,” presented by the American Statistical Association along with the AAAS. Maria Cuellar, from the University of Pennsylvania, discussed the role of statistical thinking in causal assessment, with slides that referred to a nonparametric estimator for the probability of causation. Cuellar, however, never defined what an estimator was; nor did she differentiate nonparametric from parametric estimators. She displayed other equations, again without explaining their origin and meaning, or identifying symbols or meanings. Similarly, Rochelle E. Tractenberg, discussed the use of statistics as evidence and as part of inferring causal inference in litigation, in a model of unclarity. At one point, Tractenberg appeared to suggest that general causation could be taken from regulatory pronouncements. Her discussion of glyphosate implied that general causation was established, which may have led me to disregard her presentation.

Finally, the conference sported a discussion, “Toxic Tort 2.0: Emerging Trends in Climate Change Related Litigation,” The two presenters were Dr. L. Delta Merner, the “Lead Scientist” for the Science Hub for Climate Litigation, Union of Concerned Scientists, and Dr. Paul A. Hanle, Visiting Scholar and  Founder of the Climate Judiciary Project, Environmental Law Institute. The Science Hub actively promotes climate change litigation, which made me wonder whether its scientists are involved in that new chapter in the upcoming fourth edition of the Reference Manual.

Posted in Causation, Reference Manual on Scientific Evidence, Rule 702, Scientific Evidence, Scientific Publishing | No Comments »

Lack of Trust in Science – The Situation Our Situation Is In

August 29th, 2025

The United States is in political crisis as its citizens are frogmarched into an authoritarian, illiberal, and unlawful dystopia. The seriousness of the political situation makes it difficult to focus on scientific issues, but as with past fascist regimes in history, the crisis is not limited to any one sphere of life in the United States.

Scholars of fascism have pointed out that not all fascist regimes are the same, but there are some key features that give them all a family resemblance. In the political realm, fascist leaders point to an idyllic history, however mythical or false, in which the country was once great. The greatness has been eroded and squandered by the country’s enemies, internal and external. Confronting enemies within and without is an emergency, which cannot be addressed within the rule of law. Only an authoritarian leader can fix it by suspending the rule of law.

Fascism does not operate solely in the political sphere, but insists upon ideological purity in art, culture, education, business, finance, military, law, and science.[1]

Yes, even science. Nazi Germany had its bogus science of racial purity. The Soviet Union had its Lysenkoism. Theocratic fascist regimes, such as Iran or the United States, have their “god talk” and blasphemy squads, which suppress scientific curiosity, experimentation, and development, except for the creation of weapons (where replicability, validity, and predictive accuracy really matter).

There are various reasons for Felonious Trump’s election, but the epistemic sin of credulousness of the American people is certainly one of them. We are living in Orwell’s 1984 world where many people have been tethered to TV screens to receive their daily influx of state-approved propaganda. Character for truth has ceased to be a virtue. “And even truth can become a lie in the mouth of a born liar.”[2]

The credulity of the American people has manifested as distrust in scientific expertise and willingness to believe charlatans such as Robert Kennedy, Jr. The phenomenon of transferring trust from legitimate scientists to charlatans is probably one of the clearest and strongest symptom of our current malaise.

Professor Arthur L. Caplan[3] is a scientist and medical ethicist who has never been shy about asking discomforting questions. Not surprisingly, Caplan has spoken out against some of the bone-headed anti-science actions of the present regime in Washington.[4]

In an essay entitled “How Stupid has Science Been?” Caplan asks:

“So how can U.S. President Trump, Secretary of Health Robert F. Kennedy, Jr., or Director of the Centers for Medicare and Medicaid Mehmet Oz and their enthusiastic followers be succeeding in defunding research and installing ideological oversight and censorship that is crushing science, technology and engineering and will for many years to come?”[5]

Caplan blames the scientific community itself, in part, for the current crisis by disparaging and discouraging scientists from engaging with the public. Obviously, Caplan is not thinking of the cadre of scientists who seek phony validation by becoming highly paid expert witnesses for the lawsuit industry. Nor is he thinking of the dodgy TV doctors such as Dr. Oz. Caplan’s focus is on the harm done to the careers of accomplished scientists, such as the late Carl Sagan, who was denied tenure at Harvard University and membership in the National Academies of Science because his popularizing efforts eclipsed his substantial scientific accomplishments. Caplan thus blames the American scientific establishment itself for having “disparaged its public communication as unnecessary and looked down on those few who tried to educate broader audiences about the wonders, benefits, methods and advancements of science.”

Professor Caplan argues that in popularizing scientific ideas, theories, and methods, scientists – such as the late Carl Sagan – undermined their own careers. The result is that high-achieving scientists ignored the public square and retreated into their own scientific community’s ivory tower. Caplan’s critique of the detachment of the scientific community could well be extended to its frequent failures to speak out against charlatans in its own midsts, and politicians who distort and misrepresent scientific research in the public arena.

Caplan is, however, very clear that the scientific community’s insularity, and its “resulting failure to communicate about science to the public is a major factor in explaining why so few have rallied to science’s defense today against government policies promoting ignorance, illiteracy and quackery.”  Indeed, although at this point, it is also clear that frank communications about the government’s promotion of scientific quackery will be punished by the Regime’s cancellation of grants, firing from advisory councils, and retaliations against scientists’ universities.

I take Caplan’s critique to be an invitation to engage in counter-factual thinking about what our current situation might look like if scientists had robustly “occupied the field” of communication and education of the public. Citing a recent article in a Nature journal,[6] Caplan observes that populists and right-wing thinkers have been losing faith in science for years. This diagnosis, however, is not quite accurate. Populists, left and right, have succumbed to motivated reasoning in learning to ignore scientific conclusions, regardless of validity concerns, on emotive or political grounds. This mode of (non)-thinking allows populists, left and right, to subscribe to putative scientific claims without any appreciation of the nuances of scientific inference and threats to validity.

Caplan is right to call out the right-wing attack on science, but some of the attack on science is coming from left-wing populists, such as the worm-brained Robert F. Kennedy, Jr. And historically, there have been many instances in which environmental and occupational health advocates have outrun their headlights to press claims based upon hypothetical models and unvalidated assumptions.

All people, whether they hang politically left or right, are vulnerable to the emperor of all cognitive biases – apophenia, the psychological tendency to discern causal patterns in random noise. Although apophenia was originally thought of an abnormal psychological process,[7] the phenomenon is common to “normal” as well as mentally ill persons.[8]

Many people, left and right, are willing to endorse, or subscribe to, pseudo-scientific claims based upon their motivations to accept claims, without regard to the methods used to support those claims. Professor Caplan is correct that serious scientists have been too shy to step into the public square, and the scientific community should encourage, not punish, engagement with the public. (Caplan passes over the problem of how university publicists often misrepresent and exaggerate the findings and research of university scientists.)

The problem of lack of trust in science, however, is a much bigger problem. On average, American education and acumen in math and science lags that of many countries in the world,[9] even as post-secondary education in the United States excels and attracts many of the best and the brightest domestically and internationally. Immigrants have helped American universities keep their leadership role in the world, despite shortfalls in domestic funding of primary and secondary science education. Of course, this international leadership in science and math university education, gained with the help of immigrants, is now under attack from the MAGAT regime.[10]

No one is eager to blame those who evidence their lack of trust in science, and to be sure, there is plenty of blame to go around. There are multiple systemic causes of poor quality science and improvident claims to scientific knowledge.[11] In assessing the causes of the prevalent distrust in science, we should not lose sight of the responsibility of those who claim that scientists cannot be trusted. There is at bottom a widespread moral failure in the land.  “It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence.”[12]

доверяй, но проверяй!

[1] Zachary Basu, “Trump knee-caps America’s institutions,” Axios (Aug. 27, 2025); Elisabeth Zerofsky, “Robert Paxton, A Leading Historian Of Fascism, Long Resisted Applying The Label To Trumpism. Then He Changed His Mind..,” N.Y. Times Mag. 45 (Oct. 27, 2024).

[2] Thomas Mann, “The Problem of Freedom: An Address to the Undergraduates and Faculty of Rutgers University at Convocation,” (April 28, 1939).

[3] Arthur L. Caplan, PhD., is the Drs. William F. and Virginia Connolly Mitty Professor of Bioethics, Department of Population Health, and the founder of  the Division of Medical Ethics at NYU Grossman School of Medicine’s Department of Population Health in New York City. I had the pleasure to meet Professor Caplan, and present to one of his classes, back when he taught at the University of Pennsylvania.

[4] See, e.g., Arthur L. Caplan, “Fed Action Toward Medical Journals Is ‘Dangerous’, Ethicist Says,” Medscape (Aug. 26, 2025).

[5] Arthur L. Caplan, entitled “How Stupid has Science Been?” EMBO reports (Aug. 2025).

[6] Vukašin Gligorić, Gerben A. van Kleef, and Bastiaan T. Rutjens, “Political ideology and trust in scientists in the USA,” 9 Nature Human Behaviour 1501 (2025) (“Since the 1980s, trust of science among conservatives in America has been plummeting”).

[7] See Aaron L Mishara, “Klaus Conrad (1905–1961): Delusional Mood, Psychosis, and Beginning Schizophrenia,” 36 Schizophr Bull. 9 (2009); Scott D. Blain, Julia M. Longenecker, Rachael G. Grazioplene, Bonnie Klimes-Dougan, and Colin G. DeYoung, “Apophenia as the disposition to false positives: A unifying framework for openness and psychoticism,” 129 J. Abnormal Psych. 279 (2020).

[8] Donna L Roberts, “Apophenia: The Human Tendency to Find Patterns in Randomness,” Medium (Jan. 9, 2024); Ahmed S. Sultan & Maryam Jessri, “Pathology is Always Around Us: Apophenia in Pathology, a Remarkable Unreported Phenomenon,” 7 Diseases 54 (2019).

[9] Drew DeSilver, “U.S. students’ academic achievement still lags that of their peers in many other countries,” Pew Research Center (Feb. 15, 2017).

[10] Is it not high time that we call the movement by its essential motivation: make American great again for the Trumps?

[11] See, e.g., Lex Bouter, Mai Har Sham & Sabine Kleinert, “The Lancet–World Conferences on Research Integrity Foundation Commission on Research Integrity,” 406 The Lancet 896 (2025).

[12] William K. Clifford, “The Ethics of Belief,” 29 Contemporary Rev. 289, 295 (1877).

Posted in Causation, Cognitive Biases, Scientific Evidence, Scientific Misconduct | No Comments »

Junk Journalism

August 19th, 2025

There is plenty of room for a healthy science-based environmentalism, but finding the room in the American political house has always been difficult. The current administration brings together the horseshoe wacko excesses of the worm-brained Robert Kennedy, Jr., and the crony capitalism of Felonious Trump. In this toxic, post-truth milieu, environmental groups such as Sierra Club and Greenpeace are both complaining about their setbacks,[1] as well as stepping up their own propaganda.

In the face of advocacy group propaganda, journalists should provide a strong science filter before allowing misinformation and emotive appeals to be passed off as scientific truth. Sadly, well-motivated manufacturing industry can rarely count on either the main stream media for sympathy or accuracy in reporting environmental issues. Readers of major newspapers, however, deserve careful reporting and the separation from hyperbole and fact.

A recent article in the Washington Post makes the point. Activist journalist Amudalat Ajasa reported her story this week that “Her dogs kept dying, and she got cancer. Then they tested her water.”[2] Oh my goodness; that must be a scandal; right? Queue the outrage.

Now widespread journalistic practice means that Ms. Ajasa may not have written the headline, and it was likely an editor who concocted the click-bait headline that suggested that something in the water killed some woman’s dogs and caused her cancer. Upon reading the story, however, readers would be justified in concluding that the author was clearly in on the ploy to misinform. So shame on both the would-be journalist and her editor.

Ms. Ajasa tells us that the residents of Elkton, Maryland, worry about “forever chemicals” in their water, a worry instigated in large measure by mass and social media, advocacy NGOs, state and federal agencies, and the lawsuit industry. Focusing on her anecdotal datum, Ajasa reports that Ms. Debbie Blankenship, a resident of the Elkton area, had “chalked up her health problems, including losing her right leg to an infection, to bad luck.” Bad luck? Ajasa must have gotten a HIPAA release and waiver to discuss Ms. Blankenship’s medical condition in a very public forum because the WaPo story discusses health details and features photographs of Ms. Blankenship, who is clearly obese, has had one leg amputated, and is confined to a wheel chair. Apparently, neither Ms. Blankenship nor Ms. Ajasa ever considered that lifestyle factors combined to cause Ms. Blankenship to develop diabetes mellitus and cancer (of some unspecified type).

The obvious, however, is ignored or pushed aside by Ajasa’s reporting that in 2023, W.L. Gore & Associates, a manufacturer of Gore-Tex, telephoned with a request to test the Blankenship water well for perfluorooctanoic acid (PFOA), which had been used in its manufacture of Teflon (polytetrafluoroethylene or PFTE). PFOA is one of the family of PFAS chemicals that has been the subject of a regulatory furor in recent years, including the issuance of action levels below the limits of detection for many laboratories.

The request to test the Blankenship water well was triggered by a lawsuit, filed in 2022, by a former W.L. Gore employee, Stephen Sutton. The lawsuit industry jumped on Sutton’s lawsuit with a class action environmental complaint in 2024. In any event, according to Ms. Ajasa, the company’s request to test the Blankenship well led to the eureka moment of scientific insight. Ms. Blankenship and her dogs drank well water, but her husband and children always drank bottled water. She was poisoned by the well water. Quod erat demonstrandum!

Ajasa’s reporting forces the reader to wade through a lot of activist propaganda and scientific hooey, such as claims that there is no safe level of PFOA, passed off as scientific fact. Agency assumptions and precautionary principle statements are not facts. Ignorance about no observable effect level is not knowledge that there is no safe level.

The WaPo readers are similarly regaled with a claim, masquerading as a statement of fact, that PFAS chemicals have “been linked to serious health problems including high cholesterol, cardiovascular disease, infertility, low birth weight and certain cancers.” Use of the verb “link” is a meaningless term in science, and thus a favorite of sloppy journalists. Whether a link is an association, a cause, a suggestion from an anecdote, a lawyer’s allegation, or a claim by an environmental group is anyone’s guess, and is left to the reader’s imagination. Whether Ms. Blankenship’s cancer is one of the “certain cancers” is not reported. Sloppy journalism of this sort, whether intentional, reckless, or negligent, undermines evidence-based legislation, regulation, and adjudication. “The credulous man is father to the liar and the cheat.”[3]

Ms. Ajasa eventually gets around to telling her readers that the water samples from Ms. Blankenship’s well contained PFOA concentrations of 3.4 parts per trillion (ppt), below the Environmental Protection Agency’s precautionary and unsupported maximum action level of 4 ppt. Rather than looking for other potential causes of Ms. Blankenship’s health problems, Ms. Ajasa glibly channels the EPA’s unsupported assertions that “that small amounts of the chemical can cause serious health impacts [sic], including cancer.” The reader is left to believe that this is a fact and that the undefined “small amounts” must include the 3.4 ppt detected in Blankenship’s well. Ajasa uses innuendo to substitute for the absence of evidence.

Journalists have an important role in informing and educating the public about scientific issues and controversies. Innuendo, unquestioned assumptions, and sloppy thinking – this is how the junk journalism sausage is made. Junk journalism is much like junk science. If we understand that junk journalism is a form of information pollution, then a well-considered, evidence-based environmentalism calls for remediation. 

[1] David Gelles, Claire Brown and Karen Zraick, “Environmental Groups Face ‘Generational’ Setbacks Under Trump,” N.Y. Times (Aug. 16, 2025). The list of aggrieved seems endless: Sierra Club, Greenpeace, Climate and Communities Institute, Natural Resources Defense Council, Earthjustice, the Southern Environmental Law Center, etc.

[2] Amudalat Ajasa, “Her dogs kept dying, and she got cancer. Then they tested her water,” Wash. Post (Aug. 14, 2025).

[3] William Kingdon Clifford, “The Ethics of Belief” (1877), in Leslie Stephen & Sir Frederick Pollock, eds., The Ethics of Belief and Other Essays 70, 77 (1947).

Posted in Causation, Regulation, Scientific Evidence, Scientific Publishing | No Comments »

FDA Malarky on Ingested Talc

June 6th, 2025

A couple of weeks ago, the Wall Street Journal ran an editorial that complained that FDA Commissioner Makary had touted dodgy evidence about the potential harms of talcum powder in food and medications,[1] and called an improper public meeting to discuss his concerns. The editorial noted the procedural irregularity of convening a meeting to review evidence of the supposed harms of talc in food and drugs, without proper notice and public comment.[2] The panel met just four days after the FDA’s press release.[3]

The FDA’s announcement of the irregular meeting cited last year’s IARC classification of talc in its group 2A, “probably carcinogenic” to humans, and an article in a new journal, the Journal of the Academy of Public Health, on the editorial board of which, Martin Makary sits.

The irregularity of this FDA meeting becomes even more obvious upon closer inspection. Much could be said about the irregularity of IARC classifications. The IARC defines “probably” in its 2A “probably carcinogenic” classification in a distinctly unscientific way when it reveals, in its Preamble, that its use of probably has no quantitative meaning. In attaching a 2A label to talc, the IARC rejected a conclusion that there was sufficient evidence of human carcinogenicity for talc; indeed, it found the human epidemiology on point to be “limited,” in other words, insufficient. Furthermore, the IARC’s limited conclusion was based upon a claimed association between perineal talc exposure and ovarian cancer.[4]

The irregularities abound. The FDA announced that it was convening an “independent panel of scientific experts” to explore the issue of talc in food and in drugs. And yet, one of the panelists, Daniel Cramer, has served as an expert witness for the talc lawsuit industry on multiple occasions, against Johnson & Johnson.[5] How irregular that no defense expert witness was invited to participate in the panel.

The irregularity of Daniel Cramer’s participation may be Trumped by the irregularity of the entire enterprise.  Commissioner Makary works for Secretary Robert F. Kennedy, Jr., who has spent much of his adult life advancing litigations for the lawsuit industry. Kennedy’s son, Conor, is a lawyer at Wisner Baum, a lawsuit industry firm that has cases against Johnson & Johnson.  The day of the FDA meeting, but before the panel convened, Commissioner Makary barged into another Advisory Committee meeting, convened to discuss the licensing of an unrelated anti-cancer therapeutic, and ranted about how talc was causing cancer.

Earlier this week, Commissioner Makary replied to the Wall Street Journal editorial, but failed to make his case on the science.[6] He cited IARC, but failed to disclose the meaning of the IARC classification, and to what it applied. Makary cited a 2019 Taiwanese study (Chang) that he described as having reported an association between the oral intake of talc and gastrointestinal cancer.[7] What was most irregular for a scientist who has responsibility for the FDA, however, was Makary’s failure to describe the Chang study accurately.

Chang set out to study stomach cancer, not all of gastrointestinal cancers, by looking at stomach cancer incidence in users a talc, used as a Chinese herbal, in high, medium, and low levels. The study was a typical insurance claims database study, which is interesting but which can yield only limited information. Chang and colleagues had no information about lifestyle variables such as smoking, diet, or obesity. The authors note that in Taiwan, talc is used as an antipyretic and diuretic agent, but they fail to discuss why study participants would have used an herbal remedy with such an indication for any significant length of time. To their credit, the authors excluded patients with peptic ulcer disease or Helicobacter pylori infection prior to the inclusion date. Gastritis and infection with h. pylori are potent causes of stomach cancer. Unfortunately, the information on participants’ infection status, for exclusion, was made before 1997, and so the authors had no information whether the participants who had stomach cancer actually had h. pylori infections at or near the time that they were diagnosed with stomach cancer. Helicobacter pylori infections have an attributable risk for stomach cancer of about 75%.[8] Similarly, the authors lacked information on other risk factors, such as high salt intake, pernicious anemia, EBV infection, alcohol, family predisposition, and socioeconomic status.

Using the low-exposure group as their control, the Chang study reported an adjusted stomach cancer hazard ratio of 1.58 (95% CI, 0.79 – 3.17; p = 0.19), for participants with high exposure, and an adjusted hazard ratio of 2.30 (95% CI, 1.48 – 3.57; p < 0.001) among persons with medium exposure. The authors claimed these data showed an association, but they acknowledged that the lack of a dose-response relationship made the association less likely to be causal. The association, such as it was, however, came unraveled after they excluded participants whose herbal talc use was less than five years. The exclusion, which is biologically important given that latency and induction periods for carcinogenesis are likely longer than five years, vitiated the statistically significant correlation between talc ingestion and the incidence of stomach cancer. The authors’ conclusion was thus pretty tame: “[d]espite the absence of dose-response effect, there might be a link between stomach cancer and talc.” And then again, there might not be.

Makary was not content to argue from weak and equivocal evidence. He offered a sop to the lawsuit industry and his boss, Robert F. Kennedy, Jr., by asking rhetorically whether the plaintiffs’ bar might be correct on talc. According to Makary, “They [lawsuit industry firm] were [correct] with OxyContin, Vioxx and Makena. Perhaps they will be with talc.” Well, even the blind squirrel sometimes finds a nut. OxyContin litigation turned on a marketing issue, and Makena (hydroxyprogesterone caproate), a progestin injection was withdrawn because of lack of efficacy. Even Vioxx, which had an unlabeled potential harm for a limited subgroup of users, spawn a litigation in which the lawsuit industry tried to make every user, even those who may have licked a pill for one day, a winner in the lawsuit lottery.

[1] Editorial Board, “The FDA Takes a Trial-Lawyer Turn,” Wall St. J. (May 21, 2025).

[2] FDA News Release, “FDA to Host Inaugural, Independent, Scientific Expert Panel Open to Public,” FDA (May 16, 2025).

[3] FDA Expert Panel on Talc, “Independent Expert Panel to Evaluate Safety and Necessity of Talc in Food, Drug, and Cosmetic Products,” FDA (May 20, 2025). The participants were FDA Commissioner Martin A. Makary, FDA Deputy Commissioner Sara Brenner, and a group of scientists, George Tidmarsh, John Joseph Godleski, Sandra McDonald, Daniel Cramer, Joellen Schildkraut, Malcolm Sim, Steven Pfeiffer, Nicolas Wentzensen, and Nicole C. Kleinstreuer.

[4] IARC Press Release no. 352, “IARC Monographs evaluate the carcinogenicity of talc and acrylonitrile” (July 5, 2024).

[5] See Berg v. Johnson & Johnson Consumer Co., 983 F.Supp.2d 1151, 1154 (D.S.D. 2013); Carl v. Johnson & Johnson, 464 N.J. Super. 446, 237 A.3d 308, 310 (N.J. App. Div. 2020).

[6] Makary, “The FDA Presents Its Case for Targeting Talc,” Wall St. J. (June 2, 2025).

[7] Che-Jui Chang, Yao-Hsu Yang, Pau-Chung Chen, Hsin-Yi Peng, Yi-Chia, Sheng-Rong Song & Hsiao-Yu Yang, “Stomach Cancer and Exposure to Talc Powder without Asbestos via Chinese Herbal Medicine: A Population-Based Cohort Study,” 16 Internat’l J. Envt’l Res. Public Health 717 (2019).

[8] Raghav Sundar, Izuma Nakayama, Sheraz R Markar, Kohei Shitara, Hanneke W M van Laarhoven, Yelena Y. Janjigian & Elizabeth C. Smyth, “Gastric cancer,” 405 Lancet 2087, 2089 (2025).

Posted in Asbestos, Regulation, Scientific Evidence, Talc | No Comments »

The Relative Implausibility of Relative Plausibility

May 26th, 2025

For the moment, in the American legal academy, there seems to be a fair amount of support for the idea that the burden of proof in fact-finding is centered around a vigorous contest between the plausibility of competing stories advanced by the litigants. Professors Ronald Allen and Alex Stein, two well-respected evidence law scholars have written widely about this “relative plausibility” theory of adjudication and the burden of proof.[1] They claim to “demonstrate that factfinders decide cases predominantly by applying the relative plausibility criterion guided by inference to the best explanation … .”[2] As they see American courtroom practice, the norm is “the relative plausibility mode of factfinding involving a rigorous comparison between the parties’ stories about the individual event.”[3] They insist that their “theory aligns with ordinary people’s natural reasoning.”[4]

I am not so sure. Semantically, the authors’ choice of the term “plausibility” is curious. Plausibility in ordinary usage has only a tenuous relationship with epistemic warrant. Allen and Stein acknowledge that in law (as in science and in life), the “coin of the realm is truth.” Plausibility in epistemology and philosophy of science, however, is typically treated as a weak and often irrelevant factor in assessing the correctness of a factual (scientific) claim. A leading textbook of epidemiology, for instance, offers that

“[a] causal explanation is plausible if it appears reasonable or realistic within the context in which the hypothesized cause and its effect occur. *** Plausibility can change as the context evolves and will be misleading when current understanding is misleading or wrong.”[5]

A plausible fact is not the same as a known fact, or a well-established fact. In his oft-cited after-dinner speech, Sir Austin Bradford Hill, for instance, acknowledged that plausibility is a helpful but non-necessary consideration in evaluating an association for causality, but he cautions that plausibility

“is a feature I am convinced we cannot demand. What is biologically plausible depends on the biological knowledge of the day.”

Since Hill, many scientific writers have relegated plausibility to a limited role in assessing the correctness of a causal claim. In the language of a recent effort to modernize Hill’s factors, one author noted that “plausibility and analogy do not work well in most fields of investigation, and their invocation has been mostly detrimental.”[6]

To be sure, Allen and Stein do, in some places, make clear that they take plausibility to mean more than some uninformed Bayesian prior. Relative plausibility in their view thus has some connection to the coin of the realm. At least, fact finders are seen as considering more than the usual extent of plausibility; they must “determine which of the parties’ conflicting stories makes most sense in terms of coherence, consilience, causality, and evidential coverage.”[7]

Relativity of Plausibility

If we are truly concerned with “naturalism” (ordinary reasoning?) then we should give some weight to how people react to a claim that has support. In the real world, real people are implicitly aware of Brandolini’s Law. Inspired by his reading of Daniel Kahneman’s Thinking, Fast and Slow,[8] Alberto Brandolini articulated the “Bullshit Asymmetry Principle,” in a 2013 peer-reviewed tweet. According to Brandolini, The work needed to refute bullshit is [at least] an order of magnitude greater than the work needed to produce it.

Despite its crude name, the Bullshit Asymmetry Principle has a respected intellectual provenance. In 1845, economist Frédéric Bastiat expressed an early notion of the adage:

“We must confess that our adversaries have a marked advantage over us in the discussion. In very few words they can announce a half-truth; and in order to demonstrate that it is incomplete, we are obliged to have recourse to long and dry dissertations.”[9]

Recognition of Bullshit Asymmetry actually goes back to ancient times. The Roman lawyer and teacher of rhetoric, Marcus Fabius Quintilianus, known as Quintilian to his friends, addressed the principle in his Institutio Oratoria:

“The task of the accuser is consequently straightforward and, if I may use the phrase, vociferous; but the defence requires a thousand arts and stratagems.”[10]

Quintilian’s insight explains why most people, without invoking economic efficiency or grand moral theories, believe it is natural to place the burden of proof upon the accuser or the pursuer, as opposed to the defender.

The demands made upon us by claims and “stories,” often frivolous, result in our naturally evaluating the warrant (or plausibility if you insist) for a claim before we become mired down in assessing “relative plausibility.” Courts have developed procedural mechanisms, such as summary adjudication and expert witness gatekeeping, to avoid unnecessary detailed assessments of relative plausibility. Even when cases are submitted to the factfinder, the decision may be made solely on “plausibility” of the story proffered by the party with the burden of proof.

The framing of adjudication and the burden of proof as relative plausibility seems to contradict what often happens in American courtrooms. Frequently, the defense does not put forward a “story,” but attempts to show that the plaintiff’s story is rubbish. Indeed, litigation may end without the plausibility of the defense position ever being considered. In the litigation over health claims involving exposure to Agent Orange, Judge Jack Weinstein granted summary judgment because the plaintiffs’ medical causation case was weak and insufficient.[11] The defense may have been even weaker in terms of its “coherence, consilience, causality, and evidential coverage,” but the party with the burden of proof attracts the first round of critical scrutiny in the summary judgment process. In Agent Orange, Judge Weinstein found the plaintiffs’ “proofs” to be rather crummy, without regard for the strength or weakness of the defendants’ evidence.

Similarly, Judge Weinstein granted summary judgment on plaintiffs’ claims of systemic disease injury in the silicone gel breast implant litigation. In granting judgment, Judge Weinstein pretermitted the defendants’ motions to exclude plaintiffs’ expert witnesses on grounds of Rules 702 and 703. Again, without comparison with the defendants’ “story,” Judge Weinstein found the plaintiffs’ story to be insufficient.[12]

The situation in Agent Orange and in Silicone Gel often obtains in trial itself. Defendants are often unable to disprove the plaintiffs’ claim, and the law does not require them to do so. When the evidentiary display is insufficient to support a claim, it may well be insufficient to show the claim is false. Defendants may want to be able to establish their own “story,” but the best they may have to offer is a showing that the plaintiffs’ story is not credible. Allen and Stein suggest that “[t]heoretically, a defendant can simply deny the plaintiff’s complaint, … but this virtually never occurs.”[13] They cite to no empirical evidence in claiming that “a rigorous comparison between the parties’ stories about the individual event is the norm in American courtrooms.”[14]

As shown by the summary judgment examples above, the burden of proof means something quite different from Allen and Stein’s contention about relative plausibility. Before the advent of expert witness gatekeeping, one of the few ways that a party could challenge an adversary’s expert witness was to object that the plaintiff’s medical expert witnesses offered conflicting opinions on a key factual issue in dispute. In Pennsylvania, dismissals for inconsistent expert witness opinion testimony is known as the “Mudano rule,” for a 1927 Pennsylvania Supreme Court case that held that “there must be no absolute contradiction in their essential conclusions.”[15] The Mudano rule arises because the plaintiff must furnish consistent evidence on key issues, even though the jury could otherwise freely choose to accept some or all or none of the inconsistent expert witnesses’ testimony. The Mudano rule requires dismissal without regard to the “plausibility” or implausibility of the defense case.[16]

The Mudano rule follows from the plaintiff’s having the burden of proof. When the party with the burden of proof proffers two conflicting opinions, the guesswork is simply too palpable for an appellate court to tolerate. The rule does not apply to the defense case, should the defense mange to proffer two inconsistent expert witnesses on a key issue raised by plaintiff’s case.[17]

The party without the burden of proof on causation or other key issue requiring expert witness testimony need not present any expert testimony. And if the opposing party does present expert witnesses, the law does not require that they be as precise or certain as those presented by the party with the burden. As one work-a-day appellate court put the matter:

“Absent an affirmative defense or a counterclaim, the defendant’s case is usually nothing more than an attempt to rebut or discredit the plaintiff’s case. Evidence that rebuts or discredits is not necessarily proof. It simply vitiates the effect of opposing evidence. Expert opinion evidence, such as that offered by [the defendant] in this case, certainly affords an effective means of rebutting contrary expert opinion evidence, even if the expert rebuttal would not qualify as proof.”[18]

A defendant need not engage in “story telling” at all; it may present an expert witness to testify that the plaintiff’s causation claim is bogus, even if the alternatives are merely possible. This statement of law with respect to the required certitude of expert witnesses and the burden of proof comes from a Pennsylvania case, but it appears to be the majority rule.[19]

The asymmetry created by the epistemic requirements of the burden of proof undermines the simplistic model of a court, or jury, deciding the “relative plausibility” of a claim.

Jury Instructions

The typical jury instruction on expert witness opinion testimony also shows that the burden of proof may operate without the head-to-head comparison of “stories,” as suggested by Allen and Stein. Under the law of most states, the trier of fact is free to accept some, all, or none of an expert witness opinion. In New Jersey, for instance, jurors are instructed that they

“are not bound by the testimony of an expert. You may give it whatever weight you deem is appropriate. You may accept or reject all or part of an expert’s opinion(s).”[20]

The practice of American courts with respect to burden of proof does not support the reductionist formula offered by the evidence law scholars. Burden of proof has implications in terms of summary judgment and directed verdict practice, which seem glossed over by “relative plausibility.” Furthermore, in situations in which the factfinder assesses both parties’ stories for relative plausibility, it must reject the story from the party with the burden of proof, when that party fails to show its story is more likely than not correct, even when the opponent’s story has a lesser plausibility.

Cases almost always involve incomplete evidence, and so we should expect that evidential warrant, or relative plausibility, or posterior probability of both sides’ cases to be less than complete or 100 percent.  If the party with the burden has a story with 40% probability, and then opponent’s story has a 30% probability, the case still results in a non-suit.

[1] Ronald J. Allen & Alex Stein, “Evidence, Probability, and the Burden of Proof,” 55 Ariz. L. Rev. 557 (2013) [cited herein as Allen & Stein].  They are not alone in endorsing relative plausibility, but for now I will key my observations to Allen and Stein’s early paper on relative plausibility.

[2] Id. at 4. Allen and Stein cite the classical proponents of inference to the best explanation, but they do not in this 2013 article describe or defend such inferences in detail. See Peter Lipton, Inference to the Best Explanation (2d ed. 2004); Gilbert H. Harman, “The Inference to the Best Explanation,” 74 Philosophical Rev. 88 (1965).

[3] Allen & Stein at 14.

[4] Allen & Stein at 15.

[5] Tyler J. VenderWeele, Timothy L. Lash & Kenneth J. Rothman, “Causal Inference and Scientific Reasoning,” chap. 2, in Timothy L. Lash, et al., Modern Epidemiology 17, 20 (4th ed. 2021).

[6] Louis Anthony Cox, Jr., “Modernizing the Bradford Hill criteria for assessing causal relationships in observational data,”  48 Crit. Rev. Toxicol. 682, 684 (2018).

[7] Allen & Stein at 1.

[8] Daniel Kahneman, Thinking, Fast and Slow (2011).

[9] Frédéric Bastiat, Economic Sophisms (1845), in The Bastiat Collection vol. 1, t 172 (2007).

[10] Quintilian, Institutio Oratoria, book V, chapters 13-14 (Butler transl. 1920).

[11] In re Agent Orange Product Liab. Litig., 597 F. Supp. 740, 785 (E.D.N.Y. 1984), aff’d 818 F.2d 145, 150-51 (2d Cir. 1987) (approving district court’s analysis), cert. denied sub nom. Pinkney v. Dow Chemical Co., 487 U.S. 1234 (1988); In re “Agent Orange” Prod. Liab. Litig., 611 F. Supp. 1223 (E.D.N.Y. 1985), aff’d, 818 F.2d 187 (2d Cir. 1987), cert. denied, 487 U.S. 1234 (1988). See Peter H. Schuck, Agent Orange on Trial: Mass Toxic Disasters in the Courts (1987).

[12] In re Breast Implant Cases, 942 F. Supp. 958 (E.& S.D.N.Y. 1996).

[13] Allen & Stein at 12.

[14] Allen & Stein at 14.

[15] Mudano v. Philadelphia Rapid Transit Co., 289 Pa. 51, 60, 137 A. 104, 107 (1927).

[16] See Daniel E. Cummins, “The ‘Mudano’ Rule: Conflicting Expert Opinions Often Prove Fatal,” The Legal Intelligencer (Mar. 16, 2017). See also Brannan v. Lankenau Hospital, 490 Pa. 588, 596, 417 A.2d 196 (1980) (“a plaintiff’s case will fail when the testimony of his two expert witnesses is so contradictory that the jury is left with no guidance on the issue”); Menarde v. Philadelphia Transportation Co., 376 Pa. 497, 501, 103 A.2d 681 (1954). See also Halper v. Jewish Family & Children Services of Great of Philadelphia, 600 Pa. 145, 963 A.2d 1282, 1287-88 (2009).

[17] See Kennedy v. Sell, 816 A.2d 1153, 1159 (Pa. Super. 2003).

[18] Neal v. Lu, 365 Pa. Super. 464, 530 A.2d 103, 109-110 (1987); see also Jacobs v. Chatwani, 2007 Pa. Super. 102, 922 A.2d 950, 958-960 (2007) (holding that defense expert witnesses are not required to opinion to reasonable medical certainty). See generally James Beck, “Reasonable Certainty and Defense Experts,” Drug & Device Law (Aug. 4, 2011).

[19] Jordan v. Pinamont, 2007 WL 4440900, at *2 (E.D. Pa. May 8, 2007) (“Defendants are entitled to inform the jury of other medical conditions which reasonably could have caused Plaintiff’s complaints, even if it cannot be stated to a reasonable degree of medical certainty that Defendants’ proffered alternatives were, in fact, the cause”); Johnesee v. The Stop & Shop Co., 174 N.J. Super. 426, 416 A.2d 956, 959 (N.J. Super. App. Div. 1980) (holding that defense expert witness may criticize plaintiff’s expert witness’s opinion as unfounded even though he can offer only possible alternative causes); Holbrook v. Lykes Bros. Steamship Co., 80 F.3d 777, 786 (3d Cir. 1996) (affirming admission of defense expert testimony that plaintiff had failed to exclude radiation as a possible cause of his mesothelioma, but reversing judgment for the defense on other grounds); Wilder v. Eberhart, 977 F.2d 673, 676-77 (1st Cir. 1992) (applying New Hampshire law); Allen v. Brown Clinic, P.L.L.P., 531 F.3d 568, 574-75 (8th Cir. 2008) (applying South Dakota law).

[20] N.J. CHARGE 1.13, citing State v. Spann, 236 N.J. Super. 13, 21 (App Div. 1989). See Pennsylvania’s Suggested Standard Civil Jury Instructions. PA. SSJI (Civ), § 4.100, § 4.80 (2013) (providing that the jury is not required to accept an expert witness’s testimony); Nina Chernoff, Standard jury instruction in New York on expert testimony (2023) (“You may accept or reject such testimony, in whole or in part, just as you may with respect to the testimony of any other witness.”).

Posted in Scientific Evidence, Trial Procedure | No Comments »

Judging Science Symposium

May 25th, 2025

While waiting for the much delayed fourth edition of the Reference Manual on Scientific Evidence, you may want to take a look at a recent law review issue on expert witnesses issues. Back in November 2024, the Columbia Science & Technology Law Review held its symposium at the Columbia Law Review on “Judging Science.” The symposium explored current judicial practice for, and treatment of, scientific expert witness testimony in the United States. Because the symposium took place at Columbia, we can expect any number of antic proposals for reform, as well.

Among the commentators on the presentations were Hon. Jed S. Rakoff, Judge on the Southern District of New York,[1] and the notorious Provost David Madigan, from Northeastern University.[2]

The current issue (vol. 26, no.2) of the Columbia Science and Technology Law Review, released on May 23, 2025, contains papers originally presented at the symposium:

Edith Beerdsen, “Unsticking Litigation Science.”

Edward Cheng, “Expert Histories.”

Shari Seidman Diamond & Richard Lempert, “How Experts View the Legal System’s Use of Scientific Evidence.”

David Faigman, “Overcoming Judicial Innumeracy.”

Maura Grossman & Paul Grimm, “Judicial Approaches to Acknowledged and Unacknowledged AI-Generated Evidence.”

Valerie Hans, “Juries Judging Science.”

Enjoy the beach reading!

[1] See Schachtman, “Scientific illiteracy among the judiciary,” Tortini (Feb. 29, 2012).

[2] See, e.g., In re Accutane Litig., No. 271(MCL), 2015 WL 753674 (N.J. Super., Law Div., Atlantic Cty., Feb. 20, 2015) (excluding plaintiffs’ expert witness David Madigan); In re Incretin-Based Therapies Prods. Liab. Litig., 524 F. Supp. 3d 1007 (S.D. Cal. 2021), aff’d, No. 21-55342, 2022 WL 898595 (9th Cir. Mar. 28, 2022) (per curiam). Provost Madigan is stepping down from his position next month. Sonel Cutler, Zoe MacDiarmid & Kate Armanini, “Northeastern Provost David Madigan to step down in June,” The Huntington News (Jan. 16, 2025).

Posted in Expert Witnesses, Rule 702, Scientific Evidence, statistical evidence | No Comments »

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