Daubert/Frye issues are fact specific. Meaningful commentary about expert witness decisions requires a close familiarity with the facts and data in the case under scrutiny. A recent case in point comes from the Washington Supreme Court. The plaintiff alleged that her child was born with birth defects as a result of her workplace exposure to solvents from mixing paints. The trial court dismissed the case on summary judgment, after excluding plaintiff’s expert witnesses’ causation opinions. On appeal, the Court, en banc, reversed the summary judgment, and remanded for trail. Anderson v. Akzo Nobel Coatings Inc., No. 82264-6, Wash. Sup.; 2011 Wash. LEXIS 669 (Sept. 8, 2011).
Anderson worked for Akzo Nobel Coatings, Inc., until the time she was fired, which occurred shortly after she filed a safety complaint. Her last position was plant environmental coordinator for health and safety. Her job occasionally required her to mix paints. Akzo’s safety policies required respirator usage when mixing paints, although Anderson claimed that enforcement was lax. Slip op. at 2. Anderson gave birth to a son, who was diagnosed with congenital nervous and renal system defects. Id. at 3.
Anderson apparently had two expert witnesses: one of her child’s treating physicians and Dr. Khattak, an author of an epidemiologic study on birth defects in women exposed to organic solvents. Sohail Khattak, et. al., “Pregnancy Outcome Following Gestational Exposure to Organic Solvents,” 281 J. Am. Med. Ass’n 1106 (1999). See Slip op. at 3.
The conclusions of the published paper were modest, and no claim to causality was made from either the study alone or from the study combined with the prior knowledge in the field. When the author, Dr. Khattak donned the mantle of expert witness, intellectual modest went out the door: He opined that the association was causal. The treating physician echoed Dr. Khattak’s causal opinion.
The fact-specific nature of the decision makes it difficult to assess the accuracy or validity of the plaintiff’s expert witnesses’ opinions. The claimed teratogenicity of paint solvents is an interesting issue, but I confess it is one with which I am not familiar. Perhaps others will address the claim. Regardless whether or not the claim has scientific merit, the Anderson decision is itself seriously defective. The Washington Supreme Court’s opinion shows that it did little to familiarize itself with the factual issue, and holds that judges need not tax themselves very much to understand the application of scientific principles to the facts and data of their cases. Indeed, what is disturbing about this decision is that it sets the bar so low for medical causation claims. Although Anderson does not mark a reversion to the old Ferebee standard, which would allow any qualified, willing expert witness to testify to any conclusion, the decision does appear to permit any opinion based upon a generally accepted methodology, without gatekeeping analysis of whether the expert has actually faithfully and appropriately applied the claimed methodology. The decision eschews the three subparts of Federal Rule of Evidence 702, which requires that the proffered opinion:
(1) … is based upon sufficient facts or data,
(2) … is the product of reliable principles and methods, and
(3) …[is the product of the application of] the principles and methods reliably to the facts of the case.
Federal Rule of Evidence 702.
In abrogating standards for expert witness opinion testimony, the Washington Supreme Court manages to commit several important errors about the nature of scientific and medical testimony. These errors are much more serious than any possible denial of intellectual due process in the Anderson case because they virtually ensure that meaningful gatekeeping will not take place in future Washington state court cases.
I. The Court Confused Significance Probability with Expert Witnesses’ Subjective Assessment of Posterior Probability
The Washington Supreme Court advances two grounds for abrogating gatekeeping in medical causation cases. First, the Court mistakenly states that the degree of certainty for scientific propositions is greater in the scientific world than it is in a civil proceeding:
“Generally, the degree of certainty required for general acceptance in the scientific community is much higher than the concept of probability used in civil courts. While the standard of persuasion in criminal cases is “beyond a reasonable doubt,” the standard in most civil cases is a mere “preponderance.”
Id. at 14. No citation is provided for the proposition that the scientific degree of certainty is “much higher,” other than a misleading reference to a book by Marcia Angell, former editor of the New England Journal of Medicine:
“By contrast, “[f]or a scientific finding to be accepted, it is customary to require a 95 percent probability that it is not due to chance alone.” Marcia Angell, M.D., Science on Trial: The Clash of Medical Evidence and the Law in the Breast Implant Case 114 (1996). The difference in degree of confidence to satisfy the Frye “general acceptance” standard and the substantially lower standard of “preponderance” required for admissibility in civil matters has been referred to as “comparing apples to oranges.” Id. To require the exacting level of scientific certainty to support opinions on causation would, in effect, change the standard for opinion testimony in civil cases.”
Id. at 15. This popular press book hardly supports the Court’s contention. The only charitable interpretation of the 95% probability is that the Court, through Dr. Angell, is taking an acceptable rate of false positive errors to be no more than the customary 5%, and is looking at a confidence interval based upon this specified error rate of 1 – α. This error rate, however, is not the probability that the null hypothesis is true. If the Court would have read the very next sentence, after the first sentence it quotes from Dr. Angell, it would have seen:
“(I am here giving a shorthand version of a much more complicated statistical concept.)”
Science on Trial at 114 (1996). The Court failed to note that Dr. Angell was talking about significance probability, which is used to assess the strength of the evidence in a single study against the null hypothesis of no association. Dr. Angell was well aware that she was simplifying the meaning of significance probability in order to distinguish it from a totally different concept, the probability of attribution of a specific case to a known cause of the disease. It is the probability of attribution that has some relevance to the Court’s preponderance standard; and the probability of attribution standard is not different from the civil preponderance standard.
The Court’s citation of Dr. Angell for the proposition that the “degree of confidence” and the “preponderance” standard are like “comparing apples to oranges,” is a complete distortion of Dr. Angell’s book. She is comparing the attributable risk based upon an effect size – the relative risk, which need be only greater than 50% for specific causation, with a significance probability for the interpretation of the data from a single, based upon the assumption of the null hypothesis:
“Comparing the size of an effect with the probability that a given finding isn’t due to chance is comparing apples and oranges.”
Id. This statement is a far cry from the Court’s misleading paraphrase, and is no support at all for the Court’s statistical solecism. Implicit in the Court’s error is its commission of the transpositional fallacy; it has confused significance probability (the probability of the evidence given the null hypothesis) with Bayesian posterior probabilities (the probability of the null hypothesis given all the data and evidence in the case).
Having misunderstood significance probability to be at odds with the preponderance standard, the Court notes that the “absence of a statistically significant basis” for an expert witness’s opinion does not implicate Frye or render the expert witness’s opinion inadmissible. Id. at 16. In the Anderson case, this musing is pure dictum because Dr. Khattak’s study showed a highly statistically significant difference in the rate of birth defects among women with solvent exposures compared with women without such exposures.
II. The Court Abandons Evidence or Data as Necessary to Support Judgments of Causality
The Anderson Court did not stop with its misguided distinction between burdens of proof in science and in law. The Court went on to offer the remarkable suggestion that gatekeeping is unnecessary for medical opinions because they are not, in any event, evidence-based:
“Many expert medical opinions are pure opinions and are based on experience and training rather than scientific data. We only require that ‘medical expert testimony . . . be based upon ‘a reasonable degree of medical certainty’ or probability.”
Slip op. at16 -17 (internal citations omitted). There may be some opinions that are experientially based, but the Court did not, and could not, adduce any support for the proposition that judgments of teratogenic causation do not require scientific data. Troublingly, the Court appears to allow medical expert opinions to be “pure opinions,” unsupported by empirical, scientific data.
Presumably as an example of non-evidence based medical opinions, the Anderson Court offers the example of differential diagnosis:
“Many medical opinions on causation are based upon differential diagnoses. A physician or other qualified expert may base a conclusion about causation through a process of ruling out potential causes with due consideration to temporal factors, such as events and the onset of symptoms.”
Id. at 17. This example, however, does not explain or justify anything the Court claimed. Differential diagnoses, or more accurately “differential etiology,” is a process of reasoning by iterative disjunctive syllogism to the most likely cause of a particular patient’s disease. The syllogism assumes that any disjunct – possible cause of this specific case – has previously, independently been shown to be capable of causing the outcome in question. There is no known methodology by which this syllogism itself can show general causation.
Not surprisingly, the Court makes no attempt to support its mistaken claim that differential diagnosis permits the assessment of general causation without the necessity of “scientific data.”
The Court’s confusion between significance probability (1 – α)% and posterior probability based upon all the evidence, as well as its confusion between differential diagnosis and evidence-based assessments of general causation, allowed the Court to take a short way with medical causation evidence. The denial of scientific due process followed inevitably.
III. The Court Abandoned All Gatekeeping for Expert Witness Opinion Testimony
The Anderson Court suggested that gatekeeping was required by Washington’s continued adherence to the stringent Frye test, but the Court then created an exception bigger than the rule:
“Once a methodology is accepted in the scientific community, then application of the science to a particular case is a matter of weight and admissibility under ER 702, the Frye test is only implicated where the opinion offered is based upon novel science. It applies where either the theory and technique or method of arriving at the data relied upon is so novel that it is not generally accepted by the relevant scientific community. There is nothing novel about the theory that organic solvent exposure may cause brain damage and encephalopathy. See, e.g., Berry v. CSX Transp., Inc., 709 So. 2d 552, 568 & n.12, 571-72 (Fla. Dist. Ct. App. 1998) (surveying medical literature). Nor does it appear that there is anything novel about the methods of the study about which Dr. Khattak wrote. Khattak, supra, at 1106. Frye does not require that the specific conclusions drawn from the scientific data upon which Dr. Khatta relied be generally accepted in the scientific community. Frye does not require every deduction drawn from generally accepted theories to be generally accepted.”
Slip op. at 18-19 (internal citations omitted).
By excepting the specific inferences and conclusions from judicial review, the Court has sanctioned any nonsense as long as the expert witness can proclaim that he used the methods of “toxicology,” or of “epidemiology,” or some other generally accepted branch of science. The Court left no room to challenge whether the claim is correct at any other than the most general level. The studies cited in support of a causation may completely lack internal or external validity, but if they are of a class of studies that are “scientific,” and purport to use a method that is generally accepted (e.g., cohort or case-control studies), then the inquiry is over. Indeed, the Court left no room at all for challenges to expert witnesses who give dubious opinions about medical causation.
IV. Fault Issues
Not content to banish science from the judicial assessment of scientific causality judgments, the Anderson Court went further to take away any defense based upon the mother’s fault in engaging in unprotected mixing of paints while pregnant, or the mother’s fault in smoking while pregnant. Slip op. at 20. Suing the mother as a tortfeasor may not be an attractive litigation option to the defendant in a case arising out of workplace exposure to an alleged teratogen, but clearly the mother could be at fault with respect to the causation of her child’s harm. She was in charge of environmental health and safety, and she may well have been aware of the hazards of solvent exposures. In this case, there were grounds to assert the mother’s fault both in failing to comply with workplace safety rules, and in smoking during her pregnancy (assuming that there was evidence, at the same level as paint fumes, for the teratogenicity of smoking).
