Walsworth Partner Successfully Moves to Exclude Expert Opinion Testimony in an Asbestos Case, Essentially Gutting Plaintiffs’ Case

Partner Robert Nelder scored a major victory for a firm client in an asbestos case at the outset of trial by successfully moving to exclude the opinion of plaintiffs’ only medical causation expert.

In this matter pending in San Francisco County Superior Court, plaintiff alleged that he developed multiple myeloma (a cancer of the lymphoid system) as a result of occupational exposure to the defendants’ asbestos-containing products. Plaintiffs’ medical expert was expected to testify that asbestos exposure can cause multiple myeloma; however, defendants filed a motion in limine on the eve of trial to exclude the expert’s opinion, or alternatively, to have a preliminary evidentiary hearing under California Evidence Code section 402 to determine the question of admissibility outside of the presence of the jury. The Court granted defendants’ request for a preliminary evidentiary hearing, and ultimately ruled in favor of defendants after a very contentious hearing, which lasted multiple days. The exclusion of the expert’s opinion at trial essentially decimated plaintiffs’ case against the defendants and led plaintiffs’ counsel to indefinitely delay the trial of the matter.

In making its ruling in this case, the Court noted that in order for the expert’s opinion to be admissible at trial, plaintiffs had the burden to establish that the expert’s opinion had an adequate foundation, was reliable, and was not speculative. Plaintiffs’ expert testified that he used a “weight of the evidence” approach to develop his opinion, and that when he considered various criteria such as epidemiological articles and individual case studies “in the aggregate,” it led him to conclude that asbestos causes multiple myeloma. However, the Court found that the expert failed to explain his methodology or how he weighed the evidence he considered, and did not identify what weight he gave to each piece of evidence, or why he gave the evidence the weight he did. There were also other studies that found no link between asbestos exposure and multiple myeloma, but the expert did not identify what weight, if any, he gave to those particular studies in developing his opinion in this case. Finally, plaintiffs’ expert also failed to identify any other medical or scientific expert who shared his opinion, and there were no government or health organizations that had come to the conclusion that exposure to asbestos causes multiple myeloma.

Ultimately, the Court agreed with defendants that the expert’s opinion was arbitrary and unreliable and could not be admitted at trial. Because plaintiffs’ expert could not explain how he weighed the evidence he considered, and his analysis could not be scientifically verified or replicated, the Court held that the expert’s opinion fell far short of the “medical probability” required for the admissibility of a medical causation opinion under California law.

For more information or specific guidance, please contact Margaret Mahaffey.