Knapp (defendant) was on trial for murder. In trying to prove that he killed the victim in self-defense, Knapp testified that he had heard a story that the victim, who was a police officer, clubbed and seriously injured an elderly man while in the process of arresting him. When asked, Knapp could not recall who told him the story. In response, the prosecution submitted evidence that the elderly man had actually died of senility and alcoholism and had no violent marks on his body when he died. The trial court admitted this evidence and convicted Knapp of murder. Knapp appealed.