John Perry and Robert Harding were fighting each other in Perry's house. James Beeley (defendant) intervened on Perry's behalf and punched Harding. The State of Rhode Island (plaintiff) prosecuted Beeley for assault. The trial evidence was contradictory as to whether Perry had acted in self-defense or attacked Harding without provocation. Beeley claimed that he punched Harding because he believed Perry needed help in defending himself against an intruder's attack, and that therefore he had a derivative right to self-defense. The judge instructed the jury that, no matter what Beeley believed at the time, Beeley was justified in using force on Perry's behalf only if Perry was defending himself rather than attacking Harding. The jury convicted Beeley of assault and he appealed to the Supreme Court of Rhode Island.