A recent Third Circuit decision reinforces that courts must rigorously review - and opposing parties should challenge - the reliability of experts' methodologies. In In re Zoloft (Sertraline Hydrochloride) Products Liability Litigation, the Third Circuit affirmed the district court's decision to exclude the testimony of the plaintiffs' expert statistician, Dr. Nicholas Jewell, and grant summary judgment to the defendants. The Third Circuit said Jewell invoked generally reliable scientific methodologies, but he failed to explain his deviations from the standard application of certain scientific techniques under those methodologies. The Third Circuit also confirmed that statistical significance remains an important metric to distinguish between true associations and results occurring by chance.
Here are some practical tips for challenging an expert's methodology based on the Third Circuit's decision - no matter the type of methodology an expert employs.
Third Circuit's Decision
Expert Methodology Must Be Reliably Applied
Jewell claimed Zoloft caused certain birth defects based on his examination of medical literature. He cited Bradford Hill and "weight of the evidence" methodologies to support his opinions. Epidemiologists use Bradford Hill criteria to evaluate distinctions between an association and a causal connection, using such factors as strength of an association, consistency, specificity, temporality, coherence and plausibility. The weight of the evidence analysis, however, is "a flexible methodology" that does not adhere to a particular combination of techniques. The parties agreed that both methodologies are generally reliable.
Importantly, the Third Circuit emphasized that an expert's techniques to employ a methodology must not only be reliable, but also reliably applied. The court accepted that the techniques Jewell used to implement his analysis (meta-analysis, trend analysis and reanalysis) were generally reliable. But Jewell failed repeatedly in his nonstandard application of those techniques that he used without scientific justification:
Importance of Statistical Significance Confirmed
The plaintiffs also raised a question in the appeal that led the Third Circuit to comment on the value of statistical significance. The court declined to make a "bright-line rule" that statistical significance is necessary to prove causality. Nonetheless, statistical significance "remains an important metric to distinguish between results supporting a true association and those resulting from mere chance." The Third Circuit's position is critical, given that other courts, and even the American Statistical Association, have recently questioned the value of statistical significance in assessing whether an association is causal.
The Third Circuit's decision in In re Zoloft underscores the importance of thoroughly interrogating an expert's responses to these questions:
The unmistakable message of the Third Circuit's decision is that courts should rigorously examine the techniques that experts use to arrive at their conclusions. It is not sufficient for experts to declare that their analyses used methodologies accepted as scientifically reliable in other cases. Experts' application of analytical techniques also must be reliable. If they are not, any departures from standard practice need to be explained. Failure to do so is grounds to exclude expert testimony.
Andrew Kantra is a partner in Pepper Hamilton's Health Sciences Department, a team of 110 attorneys who collaborate across disciplines to solve complex legal challenges confronting clients throughout the health sciences spectrum. Jessica Rickabaugh is of counsel in the Health Sciences Department.
The material in this publication was created as of the date set forth above and is based on laws, court decisions, administrative rulings and congressional materials that existed at that time, and should not be construed as legal advice or legal opinions on specific facts. The information in this publication is not intended to create, and the transmission and receipt of it does not constitute, a lawyer-client relationship.