Introduction Daniel Keyes's book The Minds of Billy Milligan (The Minds of Billy Milligan) represents one of the most controversial and controversial texts in the history of clinical and forensic psychology. Published in 1981, the volume tells the true story of Billy Milligan, the first American defendant acquitted of insanity based on a diagnosis of dissociative identity disorder (DID), then known as multiple personality disorder. Keyes's work lies in liminal territory betwe