“There is no expedient to which man will not resort to avoid the real labor of thinking.”
Sir Joshua Reynolds (1723-92)
Some courts appear to duck the real labor of thinking, and the duty to gatekeep expert witness opinions, by deferring to expert witnesses who advert to their reliance upon peer-reviewed published studies. Does the law really support such deference, especially when problems with the relied-upon studies are revealed in discovery? A careful reading of the Supreme Court’s decision in Daubert, and of the Reference Manual on Scientific Evidence provides no support for admitting expert witness opinion testimony that relies upon peer-reviewed published studies, when the studies are invalid or are based upon questionable research practices.[1]
In Daubert v. Merrell Dow Pharmaceuticals, Inc.,[2] The Supreme Court suggested that peer review of studies relied upon by a challenged expert witness should be a factor in determining the admissibility of that expert witness’s opinion. In thinking about the role of peer-review publication in expert witness gatekeeping, it is helpful to remember the context of how and why the Supreme was talking about peer review in the first place. In the trial court, the Daubert plaintiff had proffered an expert witness opinion that featured reliance upon an unpublished reanalysis of published studies. On the defense motion, the trial court excluded the claimant’s witness,[3] and the Ninth Circuit affirmed.[4] The intermediate appellate court expressed its view that unpublished, non-peer-reviewed reanalyses were deviations from generally accepted scientific discourse, and that other appellate courts, considering the alleged risks of Bendectin, refused to admit opinions based upon unpublished, non-peer-reviewed reanalyses of epidemiologic studies.[5] The Circuit expressed its view that reanalyses are generally accepted by scientists when they have been verified and scrutinized by others in the field. Unpublished reanalyses done for solely for litigation would be an insufficient foundation for expert witness opinion.[6]
The Supreme Court, in Daubert, evaded the difficult issues involved in evaluating a statistical analysis that has not been published by deciding the case on the ground that the lower courts had applied the wrong standard. The so-called Frye test, or what I call the “twilight zone” test comes from the heralded 1923 case excluding opinion testimony based upon a lie detector:
“Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while the courts will go a long way in admitting expert testimony deduced from a well recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.”[7]
The Supreme Court, in Daubert, held that with the promulgation of the Federal Rules of Evidence in 1975, the twilight zone test was no longer legally valid. The guidance for admitting expert witness opinion testimony lay in Federal Rule of Evidence 702, which outlined an epistemic test for “knowledge,” which would be helpful to the trier of fact. The Court then proceeded to articulate several non-definitive factors for “good science,” which might guide trial courts in applying Rule 702, such as testability or falsifiability, a showing of known or potential error rate. Another consideration, general acceptance carried over from Frye as a consideration.[8] Courts have continued to build on this foundation to identify other relevant considerations in gatekeeping.[9]
One of the Daubert Court’s pertinent considerations was “whether the theory or technique has been subjected to peer review and publication.”[10] The Court, speaking through Justice Blackmun, provided a reasonably cogent, but probably now out-dated discussion of peer review:
“Publication (which is but one element of peer review) is not a sine qua non of admissibility; it does not necessarily correlate with reliability, see S. Jasanoff, The Fifth Branch: Science Advisors as Policymakers 61-76 (1990), and in some instances well-grounded but innovative theories will not have been published, see Horrobin, “The Philosophical Basis of Peer Review and the Suppression of Innovation,” 263 JAMA 1438 (1990). Some propositions, moreover, are too particular, too new, or of too limited interest to be published. But submission to the scrutiny of the scientific community is a component of “good science,” in part because it increases the likelihood that substantive flaws in methodology will be detected. See J. Ziman, Reliable Knowledge: An Exploration of the Grounds for Belief in Science 130-133 (1978); Relman & Angell, “How Good Is Peer Review?,” 321 New Eng. J. Med. 827 (1989). The fact of publication (or lack thereof) in a peer reviewed journal thus will be a relevant, though not dispositive, consideration in assessing the scientific validity of a particular technique or methodology on which an opinion is premised.”[11]
To the extent that peer review was touted by Justice Blackmun, it was because the peer-review process advanced the ultimate consideration of the scientific validity of the opinion or claim under consideration. Validity was the thing; peer review was just a crude proxy.
If the Court were writing today, it might well have written that peer review is often a feature of bad science, advanced by scientists who know that peer-reviewed publication is the price of admission to the advocacy arena. And of course, the wild proliferation of journals, including the “pay-to-play” journals, facilitates the festschrift.
Reference Manual on Scientific Evidence
Certainly, judicial thinking evolved since 1993, and the decision in Daubert. Other considerations for gatekeeping have been added. Importantly, Daubert involved the interpretation of a statute, and in 2000, the statute was amended.
Since the Daubert decision, the Federal Judicial Center and the National Academies of Science have weighed in with what is intended to be guidance for judges and lawyers litigating scientific and technical issue. The Reference Manual on Scientific Evidence is currently in a third edition, but a fourth edition is expected in 2024.
How does the third edition[12] treat peer review?
An introduction by now retired Associate Justice Stephen Breyer blandly reports the Daubert considerations, without elaboration.[13]
The most revealing and important chapter in the Reference Manual is the one on scientific method and procedure, and sociology of science, “How Science Works,” by Professor David Goodstein.[14] This chapter’s treatment is not always consistent. In places, the discussion of peer review is trenchant. At other places, it can be misleading. Goodstein’s treatment, at first, appears to be a glib endorsement of peer review as a substitute for critical thinking about a relied-upon published study:
“In the competition among ideas, the institution of peer review plays a central role. Scientifc articles submitted for publication and proposals for funding often are sent to anonymous experts in the field, in other words, to peers of the author, for review. Peer review works superbly to separate valid science from nonsense, or, in Kuhnian terms, to ensure that the current paradigm has been respected.11 It works less well as a means of choosing between competing valid ideas, in part because the peer doing the reviewing is often a competitor for the same resources (space in prestigious journals, funds from government agencies or private foundations) being sought by the authors. It works very poorly in catching cheating or fraud, because all scientists are socialized to believe that even their toughest competitor is rigorously honest in the reporting of scientific results, which makes it easy for a purposefully dishonest scientist to fool a referee. Despite all of this, peer review is one of the venerated pillars of the scientific edifice.”[15]
A more nuanced and critical view emerges in footnote 11, from the above-quoted passage, when Goodstein discusses how peer review was framed by some amici curiae in the Daubert case:
“The Supreme Court received differing views regarding the proper role of peer review. Compare Brief for Amici Curiae Daryl E. Chubin et al. at 10, Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993) (No. 92-102) (“peer review referees and editors limit their assessment of submitted articles to such matters as style, plausibility, and defensibility; they do not duplicate experiments from scratch or plow through reams of computer-generated data in order to guarantee accuracy or veracity or certainty”), with Brief for Amici Curiae New England Journal of Medicine, Journal of the American Medical Association, and Annals of Internal Medicine in Support of Respondent, Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993) (No. 92-102) (proposing that publication in a peer-reviewed journal be the primary criterion for admitting scientifc evidence in the courtroom). See generally Daryl E. Chubin & Edward J. Hackett, Peerless Science: Peer Review and U.S. Science Policy (1990); Arnold S. Relman & Marcia Angell, How Good Is Peer Review? 321 New Eng. J. Med. 827–29 (1989). As a practicing scientist and frequent peer reviewer, I can testify that Chubin’s view is correct.”[16]
So, if, as Professor Goodstein attests, Chubin is correct that peer review does not “guarantee accuracy or veracity or certainty,” the basis for veneration is difficult to fathom.
Later in Goodstein’s chapter, in a section entitled “V. Some Myths and Facts about Science,” the gloves come off:[17]
“Myth: The institution of peer review assures that all published papers are sound and dependable.
Fact: Peer review generally will catch something that is completely out of step with majority thinking at the time, but it is practically useless for catching outright fraud, and it is not very good at dealing with truly novel ideas. Peer review mostly assures that all papers follow the current paradigm (see comments on Kuhn, above). It certainly does not ensure that the work has been fully vetted in terms of the data analysis and the proper application of research methods.”[18]
Goodstein is not a post-modern nihilist. He acknowledges that “real” science can be distinguished from “not real science.” He can hardly be seen to have given a full-throated endorsement to peer review as satisfying the gatekeeper’s obligation to evaluate whether a study can be reasonably relied upon, or whether reliance upon such a particular peer-reviewed study can constitute sufficient evidence to render an expert witness’s opinion helpful, or the application of a reliable methodology.
Goodstein cites, with apparent approval, the amicus brief filed by the New England Journal of Medicine, and other journals, which advised the Supreme Court that “good science,” requires a “a rigorous trilogy of publication, replication and verification before it is relied upon.” [19]
“Peer review’s ‘role is to promote the publication of well-conceived articles so that the most important review, the consideration of the reported results by the scientific community, may occur after publication.’”[20]
Outside of Professor Goodstein’s chapter, the Reference Manual devotes very little ink or analysis to the role of peer review in assessing Rule 702 or 703 challenges to witness opinions or specific studies. The engineering chapter acknowledges that “[t]he topic of peer review is often raised concerning scientific and technical literature,” and helpfully supports Goodstein’s observations by noting that peer review “does not ensure accuracy or validity.”[21]
The chapter on neuroscience is one of the few chapters in the Reference Manual, other than Professor Goodstein’s, to address the limitations of peer review. Peer review, if absent, is highly suspicious, but its presence is only the beginning of an evaluation process that continues after publication:
“Daubert’s stress on the presence of peer review and publication corresponds nicely to scientists’ perceptions. If something is not published in a peer-reviewed journal, it scarcely counts. Scientists only begin to have confidence in findings after peers, both those involved in the editorial process and, more important, those who read the publication, have had a chance to dissect them and to search intensively for errors either in theory or in practice. It is crucial, however, to recognize that publication and peer review are not in themselves enough. The publications need to be compared carefully to the evidence that is proffered.”[22]
The neuroscience chapter goes on to discuss peer review also in the narrow context of functional magnetic resonance imaging (fMRI). The authors note that fMRI, as a medical procedure, has been the subject of thousands of peer-reviewed, but those peer reviews do little to validate the use of fMRI as a high-tech lie detector.[23] The mental health chapter notes in a brief footnote that the science of memory is now well accepted and has been subjected to peer review, and that “[c]areful evaluators” use only tests that have had their “reliability and validity confirmed in peer-reviewed publications.”[24]
Echoing other chapters, the engineering chapter also mentions peer review briefly in connection with qualifying as an expert witness, and in validating the value of accrediting societies.[25] Finally, the chapter points out that engineering issues in litigation are often sufficiently novel that they have not been explored in peer-reviewed literature.[26]
Most of the other chapters of the Reference Manual, third edition, discuss peer review only in the context of qualifications and membership in professional societies.[27] The chapter on exposure science discusses peer review only in the narrow context of a claim that EPA guidance documents on exposure assessment are peer reviewed and are considered “authoritative.”[28]
Other chapters discuss peer review briefly and again only in very narrow contexts. For instance, the epidemiology chapter discusses peer review in connection with two very narrow issues peripheral to Rule 702 gatekeeping. First, the chapter raises the question (without providing a clear answer) whether non-peer-reviewed studies should be included in meta-analyses.[29] Second, the chapter asserts that “[c]ourts regularly affirm the legitimacy of employing differential diagnostic methodology,” to determine specific causation, on the basis of several factors, including the questionable claim that the methodology “has been subjected to peer review.”[30] There appears to be no discussion in this key chapter about whether, and to what extent, peer review of published studies can or should be considered in the gatekeeping of epidemiologic testimony. There is certainly nothing in the epidemiology chapter, or for that matter elsewhere in the Reference Manual, to suggest that reliance upon a peer-reviewed published study pretermits analysis of that study to determine whether it is indeed internally valid or reasonably relied upon by expert witnesses in the field.
[1] See Jop de Vrieze, “Large survey finds questionable research practices are common: Dutch study finds 8% of scientists have committed fraud,” 373 Science 265 (2021); Yu Xie, Kai Wang, and Yan Kong, “Prevalence of Research Misconduct and Questionable Research Practices: A Systematic Review and Meta-Analysis,” 27 Science & Engineering Ethics 41 (2021).
[2] 509 U.S. 579 (1993).
[3] Daubert v. Merrell Dow Pharmaceuticals, Inc., 727 F.Supp. 570 (S.D.Cal.1989).
[4] 951 F. 2d 1128 (9th Cir. 1991).
[5] 951 F. 2d, at 1130-31.
[6] Id. at 1131.
[7] Frye v. United States, 293 F. 1013, 1014 (D.C. Cir. 1923) (emphasis added).
[8] Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 590 (1993).
[9] See, e.g., In re TMI Litig. II, 911 F. Supp. 775, 787 (M.D. Pa. 1995) (considering the relationship of the technique to methods that have been established to be reliable, the uses of the method in the actual scientific world, the logical or internal consistency and coherence of the claim, the consistency of the claim or hypothesis with accepted theories, and the precision of the claimed hypothesis or theory).
[10] Id. at 593.
[11] Id. at 593-94.
[12] National Research Council, Reference Manual on Scientific Evidence (3rd ed. 2011) [RMSE]
[13] Id., “Introduction” at 1, 13
[14] David Goodstein, “How Science Works,” RMSE 37.
[15] Id. at 44-45.
[16] Id. at 44-45 n. 11 (emphasis added).
[17] Id. at 48 (emphasis added).
[18] Id. at 49 n.16 (emphasis added)
[19] David Goodstein, “How Science Works,” RMSE 64 n.45 (citing Brief for the New England Journal of Medicine, et al., as Amici Curiae supporting Respondent, 1993 WL 13006387 at *2, in Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993).
[20] Id. (citing Brief for the New England Journal of Medicine, et al., 1993 WL 13006387 *3)
[21] Channing R. Robertson, John E. Moalli, David L. Black, “Reference Guide on Engineering,” RMSE 897, 938 (emphasis added).
[22] Henry T. Greely & Anthony D. Wagner, “Reference Guide on Neuroscience,” RMSE 747, 786.
[23] Id. at 776, 777.
[24] Paul S. Appelbaum, “Reference Guide on Mental Health Evidence,” RMSE 813, 866, 886.
[25] Channing R. Robertson, John E. Moalli, David L. Black, “Reference Guide on Engineering,” RMSE 897, 901, 931.
[26] Id. at 935.
[27] Daniel Rubinfeld, “Reference Guide on Multiple Regression,” 303, 328 RMSE (“[w]ho should be qualified as an expert?”); Shari Seidman Diamond, “Reference Guide on Survey Research,” RMSE 359, 375; Bernard D. Goldstein & Mary Sue Henifin, “Reference Guide on Toxicology,” RMSE 633, 677, 678 (noting that membership in some toxicology societies turns in part on having published in peer-reviewed journals).
[28] Joseph V. Rodricks, “Reference Guide on Exposure Science,” RMSE 503, 508 (noting that EPA guidance documents on exposure assessment often are issued after peer review).
[29] Michael D. Green, D. Michal Freedman, and Leon Gordis, “Reference Guide on Epidemiology,” RMSE 549, 608.
[30] Id. at 617-18 n.212.
