A federal appeals court recently affirmed a judgment for the maker of a drug used to treat Parkinson’s disease in litigation alleging that the drug caused plaintiff’s compulsive gambling.  Wells v. SmithKline Beecham Corp., 2010 WL 1010591 (5th Cir. 2010).

Wells sued GlaxoSmithKline, the manufacturer of Requip, alleging that GSK had failed to warn patients about the alleged side effect of pathological gambling.  For Wells to win under Texas law,  he had to show that the failure to warn caused his injury.  Causation has two levels, general and specific, and a plaintiff must prove both. General causation is whether a substance is capable of causing a particular injury or condition in the general population, while specific causation is whether a substance caused a particular individual’s injury. Sequence matters, said the 5th Circuit: a plaintiff must establish general causation before moving to specific causation. Without the predicate proof of general causation, the tort claim fails.

Wells engaged three expert witnesses to address general causation, that the drug supposedly could cause pathological gambling. In reaching their conclusions, the experts relied upon: (1) published articles documenting case-specific correlations between Requip and gambling; (2) a single unpublished study allegedly showing a nexus between Parkinson’s medicines generally and gambling; (3)  internal data supposedly revealing case-specific associations between Requip and gambling; and (4) the fact that GSK has since changed the Requip label to warn about possible gambling side-effects. (Of course, on the last point a regulatory agency can require a warning based on a lesser level of proof than is required to recover in a tort action.) Defendant challenged the evidence under Daubert, and the district court granted summary judgment.  Plaintiff appealed.

Readers know that Daubert requires admissible expert testimony to be both reliable and relevant.  This entails a preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether that reasoning or methodology properly can be applied to the facts in issue.  Although there are “no certainties in science,” the expert must present conclusions grounded in the methods and procedures of science.  In short, the expert must employ in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field.

The court of appeals found that each of the three experts had, in deposition, in essence conceded that there exists no scientifically reliable evidence of a cause-and-effect relationship between Requip and gambling, that the state of the art was mere association, not cause.  That alone would doom the plaintiff’s case.

But more interesting for readers is when the court went on, in the alternative, to address the methodologies and fit.

The studies relied on were, each expert conceded, not statistically significant epidemiology. They were, in fact, case studies. Although case-control studies are not per se inadmissible evidence on general causation,  the courts have frowned on causative conclusions bereft of statistically significant epidemiological support. While the court agreed that in epidemiology hardly any single study is ever conclusive, and it did not suggest that an expert must back his or her opinion with multiple published studies that unequivocally support his or her conclusions, here there was simply too great an analytical gap between the data and the opinion proffered.  Bottom line– the bases for the experts’ conclusions passed none of the applicable Daubert factors: that Requip causes problem gambling is not generally accepted, has not been subjected to peer review and publication, and is not backed by studies meeting requisite scientific standards.

Without the expert testimony, Wells could not prove general causation.  Here’s a useful quote:  “Wells urges the law to lead science — a sequence not countenanced by Daubert.”  See also Rosen v. Ciba-Geigy Corp., 78 F.3d 316, 319 (7th Cir.1996) (“Law lags science; it does not lead it.”).