Another Hurdle for Expert Testimony in Texas
Medical Device Law Update
The Texas Supreme Court handed Merck another victory last year regarding Vioxx, and in the process created another hurdle to overcome for expert testimony to be admissible at trial. In Merck & Co., Inc. v. Garza, 347 S.W.3d 256 (Tex. 2011), the court threw out a judgment for the plaintiffs that came from a 2006 trial that had produced a $32 million jury verdict (which the trial judge had reduced by more than $24 million due to statutory caps on punitive damages). The court held that plaintiffs relying on epidemiological evidence to prove general causation must present at least two independent epidemiological studies showing a statistically significant doubling of the relative risk of injury for patients taking a drug under conditions substantially similar to the plaintiff's (for example, dose and duration) as compared to patients taking a placebo.
But identifying the required two studies showing a doubling of the risk is not enough. The trial court also must measure each study's methodology, design and execution against widely-accepted epidemiological standards such as the Bradford-Hill criteria to ensure each study meets minimum requirements of reliability. Additionally, plaintiffs must negate other plausible causes of their injury with reasonable certainty. Finally, plaintiffs cannot rely on the "totality of the evidence" to overcome any evidentiary shortcomings. In the court's view, if each of the individual pieces of evidence is unreliable, then the totality is unreliable as well.
Many commentators have criticized the Garza opinion for confusing general causation with specific causation. They note the "doubling of the risk" factor applies to specific causation and is an inappropriate requirement for general causation in epidemiological studies. As a consequence, it may be harder than ever for plaintiffs to present expert testimony sufficient to obtain or uphold a jury verdict in a toxic tort case.