Client Advisory

Matthew P. Moccia, Christina M. Conkling

The Second Circuit Court of Appeals recently decided two appeals, Rutledge v. Walgreen Co. and Phippen v. Walgreen Co., arising from multi-district-litigation about acetaminophen products and its relationship to attention deficit hyperactivity disorder (“ADHD”) and autism spectrum disorder (“ASD”). The precedential decision revived the underlying litigation and addressed the appropriate scrutiny a trial court should apply to disputed expert opinions. The Second Circuit was careful to note that its decision concerned only the Federal Rules of Evidence and federal expert testimony admissibility requirements, and that it was not evaluating the related political discourse, which centered around the alleged link between prenatal use of acetaminophen and ADHD and ASD, or the validity of the studies the experts in question relied on.

In Rutledge and Phippen, the District Court precluded expert testimony proffered by Plaintiff-Appellants on the ground that the experts did not reliably apply epidemiological methodologies when evaluating the relationship between Defendant-Appellee’s acetaminophen products and ADHD and ASD. Summary judgment was subsequently granted in both cases after Defendant-Appellees’ Rule 702 motions were granted excluding Plaintiff-Appellants’ experts.

The Second Circuit concluded that the District Court exceeded its discretion in excluding expert testimony provided by Plaintiff-Appellants, explaining that because the testimony in question was given by qualified experts who utilized methodologies used by other scientists in the field and included adequate interpretation of scientific evidence, it should not have been excluded.

The Court of Appeals conducted an analysis under Federal Rule of Evidence 702 and found that the District Court overstepped its role as gatekeeper by excluding expert testimony that used methodologies employed by other experts in the field, substituting its own opinions on epidemiological requirements and discrediting testimony that is subject to disagreement in the scientific community. Discussion was mostly based on the testimony of Plaintiff-Appellants’ epidemiology expert that analyzed peer-reviewed literature and applied two epidemiological methodologies concluding that there was a finding of causality between prenatal ingestion of acetaminophen products and ADHD and ASD. The District Court disagreed with this expert’s methodological choices finding that they focused on symptomatic outcomes rather than actual diagnoses of ADHD or ASD. The District Court further found that the multiple-outcomes approach that combined ADHD and ASD was limited, and the expert should have instead used separate methodologies for each diagnosis. The Second Circuit found this ruling erroneous, noting that other epidemiologists and scientists in other fields routinely used the methodology in question. It specifically noted that it was not concluding that it believed that the methodology utilized was the best option or persuasive, but that the reasons iterated by the District Court were not appropriate to exclude the testimony under Rule 702.

The Second Circuit further explained that while the causal relationship between acetaminophen and ADHD and ASD is not clear, the Federal Rules of Evidence focus on whether said methodology is routinely utilized in the relevant field rather than on the certainty of the findings. It clarified that it was up to the jury to consider the data as interpreted by Plaintiff-Appellants’ expert.

The Second Circuit further criticized the District Court’s rejection of Plaintiff-Appellants’ expert’s interpretation of the data he presented. While it acknowledged that the District Court’s concerns of cherry-picking data and experts offering testimony based on studies that goes beyond the limits that the authors set on their own studies were valid, it found that the District Court incorrectly applied its own analysis of the expert’s methodology and conclusion, noting that just because the District Court would have utilized other methodologies or interpreted the data differently, it does not render this expert’s testimony inadmissible when other experts in the field utilized the same methodology and reasonable scientists could interpret the conclusions of the studies using said methodology differently. The Court of Appeals further analyzed the District Court’s exclusion of Plaintiff-Appellants’ other experts in a similar fashion and reached the same conclusion.

This decision reflects the Second Circuit Court of Appeals’ focus on practical and narrow application of the Federal Rules of Evidence to the analysis of the validity of scientific studies relied upon in support of expert testimony even when those studies are contested or run the risk of inflaming political tensions. Its focus was on the acceptance of methodologies used in the relevant scientific communities and standards of interpretation rather than whether the expert testimony presented was compelling or persuasive.

Assuming this decision stands, defendants in the Second Circuit will have additional challenges in confronting scientifically unsupported expert opinions. Expert opinions on complicated and controversial data and claims will likely be left to the jury to decide. This decision suggests a trend towards limited application of expert evidentiary rules in the future. Attorneys practicing in the Second Circuit should be aware that challenges to the studies upon which experts rely will be evaluated on the validity of the studies’ methodology and not necessarily on the expert’s interpretation of the study or conclusion. Any challenges to an expert’s interpretation or conclusions of studies on which experts rely must be supported by objective scientific evidence and focus on the standards and general acceptance of the methodologies within the scientific community. When defending expert challenges under Rule 702, attorneys should ensure experts are aware of the validity of the methodology they are utilizing and should be prepared to offer relevant support.