New evidence suggests Mark David Chapman may not have acted alone in John Lennon's murder.

A British author and TV producer claims that a second shooter, not Mark David Chapman, may have killed John Lennon in 1980. David Whelan alleges that Chapman may have been brainwashed by the CIA to serve as a patsy. Whelan's book and documentary, "Gimme Some Truth – The Assassination of John Lennon," will be released later this year. Chapman, who pleaded guilty to the murder, is serving a 20-years-to-life sentence at Green Haven Correctional Facility in upstate New York. Chapman has been denied parole at least 12 times.