The Durham Rule is a legal standard used in the context of the insanity defense, which holds that a defendant is not criminally responsible if their unlawful act was the product of mental illness. This rule was established in 1954 by the case Durham v. United States and marked a shift towards a more inclusive understanding of mental health in legal contexts. It emphasizes the connection between mental illness and criminal behavior, allowing for a broader interpretation of insanity than previous standards.