Questionable science in the courtroom makes defending product liability suits more difficult for manufacturers. A case now on appeal to the Supreme Court of Pennsylvania involves testimony claiming that any exposure to asbestos on the job, no matter how small, is a “substantial factor” in causing mesothelioma. The NAM and other groups filed an amicus brief urging the court to reject testimony based on this “any exposure” theory, which contrasts sharply with normal causation testimony. The trial court called the theory junk science, as have many other courts, but an intermediate appellate court reversed because the judge did not constrain his ruling strictly to the arguments made by the defendants.
Our brief noted that the judge properly exercised his authority and independent judgment to identify logical and scientific errors in the "any exposure" theory. The theory shuns the bedrock principle of toxicology that "the dose makes the poison," and ignores the fact that small doses of even toxic substances may cause no harm. The "any exposure" theory could subject companies that handle any products with any degree of toxicity to expansive liability. The theory is inconsistent with asbestos science and epidemiology and runs counter to the vast majority of other court opinions.
On 5/23/2012, the Court ruled that trial judges normally should allow expert testimony, but that a hearing on the validity of the expert's testimony "is warranted when a trial judge has articulable grounds to believe that an expert witness has not applied accepted scientific methodology in a conventional fashion in reaching his or her conclusions." The judge was right to question the validity of the any-exposure opinion, particularly since it would eliminate the need for plaintiffs to pursue the more conventional route of establishing specific causation. Because the expert's opinion conflicted with itself (arguing that any exposure is a substantial cause of injury while also conceding that a disease is dose responsive), the judge did not abuse his discretion by disallowing the testimony.