In Plastics Engineering Co. v. Liberty Mut. Ins. Co., 759 N.W.2d 613 (Wis. 2009), Plenco, the insured, sought declaratory judgment that its liability insurer, Liberty Mutual, was obligated to fully defend and indemnify it in pending and future asbestos-related suits. The U.S. District Court for the Eastern District of Wisconsin granted in part and denied in part cross-motions for summary judgment. Both parties appealed, and the court of appeals certified questions of state law.

The questions certified for determination were: (1) what constitutes an ‘occurrence’ in an insurance contract when exposure injuries are sustained by numerous individuals, at varying geographical locations, over many years; (2) whether Wisconsin Statute §631.43(1) applies to successive insurance policies; and (3) whether Wisconsin courts would adopt an ‘all sums' or pro rata allocation approach to determining liability when an injury spans multiple, successive insurance policies.