Pennsylvania's Supreme Court Says 'Any Exposure' Is Not Evidence Of Specific Causation Under Frye

Pennsylvania's Supreme Court has dealt a unanimous1 blow to plaintiffs' asbestos lawyers, and potentially to plaintiffs' lawyers in a wide range of pharmaceutical, chemical and tobacco products cases requiring scientific evidence to prove specific causation. Upholding the trial court's Frye ruling, the Court rejected plaintiffs' expert's reliance on the "any exposure" theory to prove specific causation in an asbestos case. More importantly, it made plain that it is the plaintiff's burden to prove by accepted and not "novel" scientific evidence that the exposure to a particular defendant's product was sufficient to be a "substantial cause" of injury. Betz v. Pneumo Abex LLC, No. 38 WAP 2010, slip op. at 43-44 (Pa. May 23, 2012).

Background

The Supreme Court's decision in Betz arose from a global Frye challenge to the "any exposure" theory of causation brought by defendants in numerous Pennsylvania asbestos cases. That theory posits that because there is no proven "safe" dose of asbestos, any exposure to asbestos, no matter how small, may be deemed a substantial factor in the development of asbestos-related disease. Further, plaintiffs have used the "any exposure" theory to argue that every exposure from every defendants' product was a substantial cause of their disease, no matter how minimal relative to a plaintiff's cumulative lifetime exposure.

In order to resolve this global challenge, Judge Colville, presiding in the trial court, established test cases (Betz being one of them) and held a Frye hearing to evaluate the admissibility of testimony provided by plaintiffs' expert, Dr. John C. Maddox. A pathologist, Dr. Maddox testified that because all exposure can cause harm, he considered non-essential to his analysis any review of the individual exposure histories of the individual test plaintiffs. Dr. Maddox explained the theory driving his causation opinions by analogy:

The more common analogy that has been used is the example of a glass of water. One drops marbles into the glass of water until the water finally overflows from the glass. Is it the first marble or the last marble that causes the glass to overflow? Well, both, all of them. The marbles cause the glass to overflow.

Id. at 12. Defendants objected to the testimony of Dr. Maddox, arguing that the weight of the scientific literature has not demonstrated that all low dose asbestos exposure causes asbestos-related disease, and that the "any exposure" theory is therefore at odds with...