In 1950, a witness named John Christie testified that John Evans had killed his own wife and son. Despite his protestation of innocence, Evans was found guilty and hung. Three years later, it was discovered that Evans had probably been innocent after all. Christie, the crown's star witness, on the other hand, was found to be a serial killer (who had likely killed Evans's family before sending him to the gallows).
Though Christie was tried and executed, the case prompted such revulsion against the death penalty that Parliament was forced to abolish it.