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.

From approximately 1950 until 1983, Plenco manufactured and sold certain compounds that incorporated asbestos. Plenco was now a defendant in a number of lawsuits because of bodily injury or wrongful death that were allegedly related to or had arisen from exposure to asbestos-containing products sold by Plenco. The claimants alleged that they were injured by their first exposure to asbestos, but their asbestos-related injuries did not manifest until long after their exposure. The exposures allegedly occurred at different times and at different geographical locations.