The nonfiction work The Minds of Billy Milligan documents the life and experiences of William Stanley “Billy” Milligan, opening with Milligan’s arrest and subsequent trial for the rape of three women on the Ohio State University Campus. Milligan’s case was a landmark event in two fields, law and psychiatry, providing a previously unprecedented intersection in US history. The book even explores this as one of the central themes.

Milligan’s case was a landmark event in US legal history, because he was the first person declared not guilty by reason of insanity specifically because of a diagnosis of “multiple personality disorder,” now known as dissociative identity disorder (DID). The book touches on how Milligan’s lawyers wondered whether they could win an insanity plea because at the time “multiple personality disorder” was classified as neurosis rather than psychosis. Since only the latter indicates a break from reality, even given Milligan’s eventual diagnosis of “multiple personality disorder,” his being declared not guilty by reason of insanity was a first.

The verdict in the case may have differed had events transpired at a later point in time. Shortly before Milligan’s trial began, a change of law shifted the burden of proof of insanity to the defense, rather than the burden of proof of sanity lying with the prosecution.