Billy Milligan was an American man known for being one of the first people diagnosed with Dissociative Identity Disorder (formerly known as multiple personality disorder). In the late 1970s, he gained national attention after being arrested for a series of crimes, including robbery and rape. During his trial, it was revealed that he had 24 distinct personalities, which led to a controversial legal defense claiming he was not responsible for his actions due to his mental condition. Milligan's case raised important questions about mental health and the legal system. His story was later documented in the book "The Minds of Billy Milligan" by Daniel Keyes and inspired various adaptations, including films and documentaries. Milligan's life highlighted the complexities of identity and the challenges faced by individuals with severe mental health issues.