In Parker v Mobil Oil Corp., 2006 NY Slip Op 07391, the New York Court of Appeals clarified the ways in which a plaintiff may prove causation through the use of expert testimony in a toxic tort case.
The Court first noted that when determining whether the plaintiff's experts' methodologies lead to a reliable result, the appropriate inquiry is whether the there is an appropriate foundation and thus analysis under Frye is unnecessary.
The Court then concluded that in toxic tort cases, a plaintiff is not limited to one particular method when establishing causation, but that the method used must pass the Frye test:
(I)t is not always necessary for a plaintiff to quantify exposure levels precisely or use the dose-response relationship, provided that whatever methods an expert uses to establish causation are generally accepted in the scientific community....
There could be several other ways an expert might demonstrate causation. For instance, amici note that the intensity of exposure to benzene may be more important than a cumulative dose for determining the risk of developing leukemia. Moreover, exposure can be estimated through the use of mathematical modeling by taking a plaintiff's work history into account to estimate the exposure to a toxin. It is also possible that more qualitative means could be used to express a plaintiff's exposure. Comparison to the exposure levels of subjects of other studies could be helpful provided that the expert made a specific comparison sufficient to show how the plaintiff's exposure level related to those of the other subjects. These, along with others, could be potentially acceptable ways to demonstrate causation if they were found to be generally accepted as reliable in the scientific community.
The Court then determined that in the case at hand, wherein the plaintiff alleged that his exposure to benzene in gasoline caused him to develop acute myelogenous leukemia (AML), the plaintiff's experts' opinions were properly excluded since the experts "failed to demonstrate that exposure to benzene as a component of gasoline caused Parker's AML."
This opinion is worth a read even if you don't handle toxic torts matters, if only for the Court's analysis of causation issues. However, be forewarned. The decision is pretty dense--it's a good one to keep by your bedside, should you suffer from insomnia.