Arnstein v. Porter
United States Court of Appeals for the Second Circuit
154 F.2d 464 (1946)
Arnstein (plaintiff) sued Porter (defendant) for copyright infringement, claiming Porter's employees broke into his apartment to access his music, though Arnstein had no corroborating evidence for that claim beyond his own testimony; the district court granted Porter summary judgment, and the works showed some similarity though not enough to unquestionably infer copying absent proof of access.
Whether, in an action for copyright infringement, the plaintiff must prove that the defendant copied from the plaintiff's copyrighted work and that the copying went so far as to constitute improper appropriation, and whether summary judgment is proper if a case will be resolved based on a determination of a witness's credibility.