Kirk (plaintiff) brought a personal injury suit against Owens-Corning (defendant) for asbestos-related injuries. Owens-Corning introduced expert testimony of Dr. Harry Demopoulos, who stated that the “overwhelming majority” of asbestos-related mesotheliomas are caused by crocidolite asbestos fiber. Kirk then introduced, over Owens-Corning’s objection, the prior testimony of Dr. Louis Burgher from an unrelated Owens-Corning litigation. In that prior testimony, Burgher testified for Owens-Corning that chrysotile fibers contaminated with tremolite could cause mesothelioma. The United States District Court for the Eastern District of Pennsylvania admitted the prior testimony and found in favor of Kirk. Owens-Corning appealed.