Tal Golan’s Preliminary History of Epidemiologic Evidence in U.S. Courts

Tal Golan  is an historian, with a special interest in the history of science in the 18th and 19th centuries, and in historical relationships among, science, technology, and the law.  He now teaches history at the University of California, San Diego.  Golan’s  book on the history of expert witnesses in the common law is an important starting place in understanding the evolution of the adversarial expert witness system in English and American courts.  Tal Golan, Laws of Man and Laws of Nature: A History of Scientific Expert Testimony (Harvard 2004).

Last year, Golan led a faculty seminar at the University of Haifa’s Law School on the history of epidemiologic evidence in 20th century American litigation.  A draft of Golan’s paper is available at the school’s website, and for those interested in the evolution of the American courts’ treatment of statistical and epidemiologic evidence, the paper is worth a look.  Tal Golan, “A preliminary history of epidemiological evidence in the twentieth-century American Courtroom” manuscript (2011) [Golan 2011].

There are problems, however, with Golan’s historical narrative.  Golan points to tobacco cases as the earliest forays into the use of epidemiologic evidence to prove health claims in court:

“I found only four toxic tort cases in the 1960s that involved epidemiological evidence – two tobacco and two vaccine cases. In the tobacco cases, the plaintiffs tried and failed to establish a causal relation between smoking and cancer via the testimony of epidemiological experts. In both cases the judges dismissed the epidemiological evidence and directed summary verdicts for the tobacco companies.38

Golan 2011 at 11 & n. 38 (citing Pritchard v. Liggett & Myers Tobacco Co., 295 F.2d 292 (1961); Lartigue v. R.J. Reynolds Tobacco Co., 317 F.2d 19 (1963)).  Golan may be correct that some of the early tobacco cases were dismissive of statistical and epidemiologic evidence, but these citations do not support his assertion.  The Latrigue case resulted in a defense verdict after a jury trial.  The judgment for the defendant was affirmed on appeal, with specific reference to the plaintiff’s use of epidemiologic evidence.  Lartigue v. R.J. Reynolds Tobacco Co., 317 F.2d 19 (5th Cir. 1963) (“The plaintiff contends that the jury’s verdict was contrary to the manifest weight of the evidence. The record consists of twenty volumes, not to speak of exhibits, most of it devoted to medical opinion. The jury had the benefit of chemical studies, epidemiological studies, reports of animal experiments, pathological evidence, reports of clinical observations, and the testimony of renowned doctors. The plaintiff made a convincing case, in general, for the causal connection between tobacco and cancer and, in particular, for the causal connection between Lartigue’s smoking and his cancer. The defendants made a convincing case for the lack of any causal connection.”), cert. denied, 375 U.S. 865 (1963), and cert. denied, 379 U.S. 869 (1964).  Golan is thus wrong to suggest that the plaintiffs in Lartigue suffered a summary judgment or a directed verdict on their causation claims.

In Pritchard, the plaintiff had three trials in the course of litigating his tobacco-related claims.  See Pritchard v. Liggett & Myers Tobacco Co., 134 F. Supp. 829 (W.D. Pa. 1955), rev’d, 295 F.2d 292, 294 (3d Cir. 1961), 350 F.2d 479 (3d Cir. 1965), cert. denied, 382 U.S. 987 (1966), amended, 370 F.2d 95 (3d Cir. 1966), cert. denied, 386 U.S. 1009 (1967).  The Pritchard case ultimately turned on liability more than causation issues.  In both cases, Golan’s citations are abridged and incorrect.

Golan also wades into a discussion of statistical significance in which he misstates the meaning of the concept and he incorrectly describes how it was handled in at least one important case:

“Statistics provides such an assurance by calculating the probability of false association, and the epidemiological dogma demands it to be smaller than 5% (i.e, less than 1 in 20) for the association to be considered statistically significant.”

Golan 2011, at 18.  This statement is wrong.  Statistics do not provide a probability of the truth or falsity of the association.  The significance probability to which Golan refers measures the probability of data at least as extreme as those observed if the null hypothesis of no difference is correct.

Having misunderstood and misstated the meaning of significance probability, Golan proceeds to make the classic misidentification of statistical significance probability with the probability of the either the null hypothesis or the observed result.  Frequentist statistical testing cannot do this, and Golan’s error has no place in a history of these concepts other than to point out that courts have frequently made this mistake:

“The ‘statistical significance‘ standard is far more demanding than the ‘preponderance of the evidence‘ or ‘more likely than not‘ standard used in civil law. It reflects the cautious attitude of scientists who wish to be 95% certain that their measurements are not spurious.

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Epidemiologists have considered the price well worth paying. So has criminal law, which emphasizes the minimization of false conviction, even at the price of overlooking true crime. But civil law does not share this concern.”

This narrative misstates what epidemiologist are doing in using significance probability and null hypothesis significance testing.  The confusion between epidemiologic statistical standards and burden of proof in criminal cases is a serious error.

Golan compares and contrasts the approaches of the trial judges in Allen v. United States, and in In re Agent Orange:

“Judge Weinstein, on the other hand, was far less concerned with the strictness of the epidemiology. A scholar of evidence, member of the Advisory Committee that drafted the Federal Rules of Evidence during the early 1970s, and a critic of the partisan deployment of science in the adversarial courtroom, Weinstein embraced the stringent 95% significance threshold as a ready-made admissibility test that could validate the veracity of the statistical evidence used in court. Thus, while he referred to epidemiological studies as ―the best (if not the sole) available evidence in mass exposure cases,‖ he nevertheless refused to accept them in evidence, unless they were statistically significant.64

Golan at 19.  Weinstein is all that and more, but he never simplistically embraced statistical significance as a “ready-made admissibility test.”  Of course 95% is the coefficient of confidence, and the complement of alpha of 0.05%, but this alpha is not a particularly stringent threshold unless it is misunderstood as a burden of proof.  Contrary to Golan’s suggestion, Judge Weinstein was not being conservative or restrictive in his approach in In re Agent Orange.

Golan’s “preliminary” history is a good start, but it misses an important perspective.  After World War II, biological science, in the form of genetics, as well as epidemiology and other areas, grew to encompass stochastic processes as well as mechanistic processes.  To a large extent, in permitting judgments to be based upon statistical and epidemiologic evidence, the law was struggling to catch up with developments in science.   There is quite a bit of evidence that the law is still struggling.

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