Medical Case Studies As Expert Evidence

In failure to warn of drug side effect case, excluding under FRE 702 plaintiff's experts' testimony regarding a causal link between defendant's medication for plaintiff's Parkinson's disease symptoms (Requip) and the plaintiff's compulsive gambling; the experts testimony of a positive relation between Requip and gambling which was grounded "primarily on the scientific literature," that was "'anecdotal evidence,' and each expert conceded that the studies were not statistically significant epidemiology. They were, in fact, case studies,'" in Wells v. SmithKline Beecham Corp., 601 F.3d 375, 379-80 (5th Cir. 2010) (N0. 09-50244)

The "Case Study" Problem

Can anecdotal or case study reports provide sufficient support for expert opinion testimony? Would such evidence support a finding that would be generally recognized by the courts? The Fifth Circuit had occasion to consider the value of anecdotal reports as a basis for assessing whether there was any basis for a plaintiff's case in medical science. The circuit agreed with the trial judge that the evidence was insufficient to show the general causation necessary to prevail in a failure to warn product liability action.

In the case, plaintiff Wells brought a diversity failure to warn product liability suit against defendant SmithKline. Wells alleged that he suffered an unwarned after-effect of the drug that the defendant made. The drug, Requip, had been prescribed to the plaintiff for treatment of his Parkinson's disease. The plaintiff contended that the defendant had failed to warn users that Requip "could make him gamble away millions." To support his claim that his "pathological gambling" was a result of taking Requip, he offered the testimony of three expert witnesses that the drug "can cause pathological gambling...." Wells, 601 F.3d at 376.

Experts' Statements

The circuit briefly described deposition testimony by three expert witnesses the plaintiff presented on causation. Each expert essentially back-petaled about the necessary relation between the defendant's drug and the plaintiff's gambling. As summarized by the circuit, the witnesses provided testimony on the relation or association between the drug and the gambling, but they admitted it did not constitute "direct" causation as was a necessary showing under applicable state tort law:

  • Dr. Fong: "I think fundamentally there is something very compelling and interesting going on here, but we don't have enough data to suggest causality .... I have not come to a conclusion that there is a causal relationship between Requip and pathological gambling.” He further testified that-based on the “scientific standard that [he] appl[ies] in [his] practice as a psychiatrist and a research scientist”-the scientific literature did not establish a “cause-and-effect relationship between Requip and pathological gambling.”
  • Dr. Saklad: He was asked: “Applying the scientific standard for cause and effect, has-has a cause-and-effect relationship been established between taking Requip and having one or more impulse-control disorders considered as a collective group?” He answered: “No.”
  • Dr. Kalechstein: The circuit noted that this witness was "more hesitant at first, [but] "ultimately fell in line with Fong and Saklad: “I cannot say [Requip] directly causes [pathological gambling]. What I can say is that there is an association between the two variables .... [T]hat's different than talking about the issue of causation.”
Wells, 601 F.3d at 379.

Insufficient Basis For Showing Causation

The circuit concluded that the three experts' testimony was not sufficient to avoid summary judgment for the defendant:

The experts based their general causation conclusion primarily on the scientific literature, which they claim shows an association between Requip and problem gambling. The literature, though, does not provide the necessary “scientific knowledge” upon which to base an opinion under Daubert. Doctor Fong characterized all but one of the studies as “anecdotal evidence,” and each expert conceded that the studies were not statistically significant epidemiology. They were, in fact, case studies. Although, “[c]ase-control studies are not per se inadmissible evidence on general causation,” this court has frowned on causative conclusions bereft of statistically significant epidemiological support.
Wells, 601 F.3d at 379-380 (footnotes omitted) (citing Burleson v. Tex. Dep't of Criminal Justice, 393 F.3d 577, 586 (5th Cir. 2004) (“Here, as in Allen, there are no epidemiological studies supporting a correlation between the suggested causative agent and the type of cancer experienced by the plaintiff.”); Allen v. Pa. Eng'g Corp., 102 F.3d 194, 197 (5th Cir. 1996) (“While appellants' experts acknowledge the lack of statistically significant epidemiological evidence, they rely on certain studies as ‘suggestive’ of a link between EtO exposure and brain cancer. ‘Suggestiveness' is not by the experts' own admission statistical significance ...; this basis for their scientific opinion must be rejected.”)).


The trial court did not err in granting summary judgment to the defendant. At most the plaintiff was able to show only that "[p]erhaps Requip is a cause of problem gambling, but the scientific knowledge is not yet there. Wells urges the law to lead science-a sequence not countenanced by Daubert. And while the possibilities of their relationship properly spark concerns sufficient to warrant caution, the courts must await its result." The Fifth Circuit's analysis in Wells suggests that when presented with only case-studies indicating that that an illness generally follows exposure, without anything more in terms of medical testing and analysis, it is unlikely that a federal court would admit the evidence.


Federal Rules of Evidence