The Pennsylvania Supreme Court has decided a product liability case that required it to reexamine the state’s standards for the admission of expert witness testimony.

Walsh’s Death

Thomas Walsh served as the groundskeeper and superintendent at several Pittsburgh area golf courses for almost 40 years. His work involved the regular application of pesticides. On October 5, 2008, Walsh was diagnosed with Acute Myelogenous Leukemia. On February 2, 2009, died. His oncologist, James Rossetti, D.O., opined that Walsh’s extensive exposure to pesticides raised a high degree of suspicion that the exposure played a significant role in the development of his AML.

Trial Court

Walsh’s executor initiated a wrongful death and survival action against the manufacturers of the various pesticides that Walsh had applied over his career. The lawsuit raised claims in strict products liability, negligence, and breach of warranty. The trial court granted summary judgment in favor of a large number of manufacturers based upon a lack of expert testimony identifying their pesticides as substantial contributing factors in Walsh’s death.

The remaining manufacturers filed Frye motions to exclude two of the executor’s expert witnesses, Nachman Brautbar, M.D, and April Zambelli-Weiner, Ph.D. The motions claimed that Drs. Brautbar and Zambelli-Weiner failed to apply methodologies generally accepted in the relevant scientific communities. Following a review of depositions and briefs filed by each party, the trial court granted the Frye motions. Following the trial court’s grant of the Frye motions, the parties stipulated to summary judgment in favor of all remaining defendants.

Superior Court

The executor appealed to the Superior Court. On appeal, the superior court reversed the trial court’s grant of the Frye motions. The court ruled that the expert opinions that pesticides in general could cause cancer in general were admissible under Pennsylvania’s Frye framework for evaluating expert testimony, and sufficient to preclude summary judgment as to the pesticide products of fourteen different manufacturers.

Pennsylvania Supreme Court

The defendants appealed to the Pennsylvania Supreme Court, asking it to review the following:

(1) Did the Superior Court majority commit reversible error in concluding that, when evaluating scientific evidence under the Frye standard, trial courts are not permitted to act as “gatekeepers” to ensure the relevance and reliability of scientific studies offered by experts to support their opinions by scrutinizing whether those studies actually support their opinions?

(2) Did the Superior Court majority commit reversible error in concluding that trial courts may not review experts’ opinions extrapolating from a broad class of products and injuries to a specific product and injury, thereby eliminating plaintiff’s burden to show product-specific causation of plaintiff’s specific injury?

(3) Did the Superior Court majority commit reversible error in concluding that the trial court erred without explaining how it abused its discretion because of manifest unreasonableness, partiality, prejudice, bias, ill-will or such lack of support from the evidence or the record so as to be clearly erroneous?

Addressing the first “gatekeeping” issue, the Pennsylvania Supreme Court affirmed the Superior Court’s decision, but did not give a clear ruling about the trial court’s role as gatekeepers. The court stated that “the trial court must be guided by scientists in the relevant field, including the experts retained by the parties in the case and any other evidence of general acceptance presented by the parties.”

For the second extrapolation issue, the Supreme Court ruled that the record did not show that the plaintiff’s experts used extrapolation in the way that the defendants claimed. It stated, “while both experts employed the Bradford Hill criteria to establish a causal link between cancer (or AML) and long-term exposure to pesticides, neither expert opined that this link wholly constituted product-specific causation between cancer and long-term exposure to the Appellants’ specific pesticide products.”

For the third abuse of discretion issue, the court ruled that it is an abuse of discretion for a trial judge “to make its own bald judgments about which studies relied upon by [an expert] were scientifically acceptable, relevant and/or supportive of [the expert’s] conclusions.”

The court then affirmed the order of the Superior Court and remanded the matter to trial court for the defendants to renew their Frye motions in line with the Supreme Court’s opinion.