On June 14, 2017, the California Supreme Court issued an order declining to clarify the evidentiary threshold that must be met to prove causation in asbestos litigation. The decision was a setback for WLF, which filed a letter brief urging the Court to provide much needed guidance on whether the “every exposure” theory of causation provided in expert testimony is admissible in California toxic tort cases. The verdict below was based on expert witness testimony that any exposure to asbestos over the course of a lifetime substantially contributes to the risk of disease. The Court of Appeal, and other lower California courts, have allowed plaintiffs to establish causation based on this “every exposure” theory. Because the Court set a higher threshold for causation 23 years ago in Rutherford v. Owens-Illinois, Inc., WLF urged the Court to take this opportunity to clarify the “substantial factor” test it set out then.