Every Bit Counts in Asbestos Litigation: Surprising Ruling on Exposure Theory Might be Boon for Plaintiffs


In Davis v. Honeywell International Inc., plaintiff brought a wrongful death suit against a manufacturer of asbestos-containing brake lining after her father passed away from mesothelioma. In the recent appellate decision, the Court held that the trial court did not abuse its discretion in admitting expert testimony based on the “every exposure theory.” This appellate decision is troubling as it marks a departure from traditional theories of causation in asbestos litigation.

Asbestos plaintiffs use the “every exposure theory” to establish causation or to show a particular exposure had a causal relationship with the injury. According to the theory, “every exposure to asbestos contributes to the formation of mesothelioma regardless of different varieties of asbestos with varying potencies as long as the exposure was more than no exposure at all. This theory is particular distressing because it permits an expert to disregard relevant features of toxic exposure such as amount, duration, and intensity, in spite of the fact that mesothelioma is a dose/response disease. Instead, the expert need only rely on reports or conjecture to opine that any exposure equals causation.

Traditionally, in asbestos litigation, courts excluded causation opinions based on the “every exposure theory" for two primary reasons. First, the theory does not provide the reliable methodology to develop a causation opinion and is not based on accepted epidemiological studies. Second, the theory ignores the underlying facts of the case specifically with respect dosage, nature or amount of exposure, and the role of alternative potential exposure.

In Davis, Plaintiff presented expert testimony in support of her claim that her father’s exposure to asbestos in Bendix brake linings, while performing one to two brake jobs a day in the 1960s and 1970s, was a substantial factor in contributing to his risk of developing mesothelioma. On appeal, defendant, Honeywell International Inc. (“Honeywell”), argued Plaintiff’s expert testimony using the “every exposure theory” should have been excluded for lack of evidentiary and logical support. Honeywell also argued the theory is contrary to the California Supreme Court’s holding inRutherford v. Owens Illinois (1997) 16 Cal.4th 953, where the court held causation must be proven by demonstrating that exposure to the defendant’s product, in reasonable medical probability, was a substantial factor in contributing to risk of disease. However, the Davis court diminished Honeywell’s arguments and held that many asbestos plaintiffs prove causation by presenting medical expert testimony adopting the theory that even low doses of asbestos contribute to the development of mesothelioma.

The Davis court concluded “because in ruling on the admissibility of expert testimony the trial court ‘does not resolve scientific controversies’, it is for the jury to resolve the conflict between the every exposure theory and any competing expert opinions.” Therefore, the Davis court held the trial court did not abuse its discretion in allowing plaintiff’s medical expert to testify.

This signals a striking departure from previous court holdings that have rejected efforts to use the contentious theory to say that every asbestos exposure is a substantial factor in causing the disease. Moreover, the obligation of courts to be a gate keeper and to keep unsupported science out of the courtroom is in jeopardy when a seriously flawed and shaky theory such as the “every exposure theory” can make its way into trial by expert testimony.

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