Duplan Corp. v. Moulinage et Retorderie de Chavanoz

Duplan and other plaintiffs sued Chavanoz and others (defendants) for Sherman Act violations over patents on false-twist machines, with 37 related cases consolidated for trial. Duplan sought discovery of Chavanoz's attorneys' work product from earlier, separate litigation against a different company over the same patents. On an earlier appeal, the Fourth Circuit had already held that work product doesn't become freely discoverable in later, unrelated litigation just because the original case ended. On remand, the district court ordered Chavanoz to produce documents containing attorneys' "mental impressions, conclusions, opinions, and legal theories," reasoning that Duplan had shown a substantial need for the material and undue hardship in obtaining it elsewhere. Chavanoz appealed.