The Durham Rule is a legal standard used to determine criminal responsibility. It states that a defendant is not criminally responsible if their unlawful act was the result of a mental illness. This rule emphasizes the connection between mental health and behavior, suggesting that individuals who cannot control their actions due to a mental disorder should not be held fully accountable. This rule originated from a 1954 case involving John W. Hinckley Jr., who was found not guilty by reason of insanity. The Durham Rule was later replaced by the more widely used M'Naghten Rule, which focuses on the defendant's ability to understand right from wrong.