Leonardo DiCaprio has signed on to star in and produce an adaptation of The Crowded Room, where the actor will play the role he's been eyeing for nearly 20 years, Billy Milligan, the first person to successfully use multiple personality disorder as a defense in a court of law. New Regency will produce alongside Leonardo DiCaprio's company Appian Way, with screenwriters Jason Smilovic and Todd Katzberg coming aboard to write the screenplay adaptation. The project is based on the 1981 non-fiction book The Minds of Billy Milligan by Daniel Keyes.

Billy Milligan was charged with robbery and the rapes of three women on the Ohio State University campus in the 1970s. While preparing for his defense, Milligan was diagnosed with multiple personality disorder, and he plead not guilty by reason of insanity, which was caused by multiple personality disorder. Milligan and his lawyers contended that two of his 24 separate personalities committed the crimes without his knowledge. He was the first to ever use this defense, and also the first to be acquitted as well. Among Milligan's personalities were Adalena, a lesbian who fessed up to the rapes, Ragan, a Yugoslavian communist who admitted to the robberies, and a stuffy Englishman named Arthur. Milligan died in 2014.

Leonardo DiCaprio will produce with his Appian Way partner Jennifer Davisson Killoran and Alexandra Milchan. The project had been swirling around Hollywood for several years, with James Cameron among one of many filmmakers who have expressed interest in bringing this story to the big screen. Leonardo DiCaprio has talked about playing Milligan since 1997, and now the project is finally coming to fruition. The movie also strengthens the actor-producer's ties with New Regency, who are currently collaborating on The Revenant with Birdman director Alejandro González Iñárritu.