Chapter 27 is a 2007 biographical drama film depicting the murder of John Lennon by Mark David Chapman. It was written and directed by Jarrett Schaefer, based on the book Let Me Take You Down by Jack Jones, produced by Robert Salerno, and stars Jared Leto as Chapman. The film takes place in December 1980, and is intended to be an exploration of Chapman's psyche. Its title is a reference to J. D. Salinger's novel The Catcher in the Rye, which has twenty-six chapters, and suggests a continuation of the book.

The script took Schaefer four years to write, but when it was finished, the film came together quickly. With the help of producers Alexandra Milchan and Robert Salerno, Schaefer cast Jared Leto as Mark David Chapman. For his role, Leto gained 67 pounds (30 kg) by drinking microwaved pints of ice cream mixed with soy sauce and olive oil every night. Gaining the weight, he said, was tougher than dieting himself into skeletal shape for his role as drug addict Harry Goldfarb in Requiem for a Dream (2000). The abruptness of Leto's weight gain gave him gout. He had to use a wheelchair due to the stress of the sudden increase in weight put on his body.  After the shooting of the film, Leto quickly went on a liquid diet. He explained, "I've been fasting ever since. I've been doing this very strange, like, lemon and cayenne pepper and water fast. I didn't eat any food for 10 days straight; I think I lost 20 pounds that first 10 days." Losing the excess weight after Chapter 27 proved a challenge. "It took about a year to get back to a place that felt semi-normal," he said; "I don't know if I'll ever be back to the place I was physically. I'd never do it again; it definitely gave me some problems."  Twenty-two years prior to this film's production, actor Mark Lindsay Chapman, while professionally using the name Mark Lindsay, had been almost cast as John Lennon in the biopic John and Yoko: A Love Story (1985). Yoko Ono had been deeply involved in the production and had herself been initially impressed with his audition and approved his casting prior to discovering his full name was Mark Lindsay Chapman. She then nixed his casting on the grounds it was "bad karma", and a great deal of press attention was given to his having almost gotten the role. The director of Chapter 27, Jarrett Schaefer, auditioned many Lennon impersonators, but was especially impressed with Mark Lindsay Chapman's tape because he conveyed the "tough town" street-smart quality of Lennon that the impersonators failed to convey, as they always played Lennon as larger-than-life. Schaefer described Lennon as having a "chip on his shoulder and always cracking these cynical one-liners", and felt that actor Chapman was best at conveying this quality. Schaefer had some difficulty negotiating the casting with the film's producers because of Chapman's name. After Chapman was cast, he asked Chapman how he should be billed to which Chapman replied "Mark fucking Lindsay Chapman. That's my fucking name." Schaefer remarks that this was so reflective of how Lennon talked, it just reinforced his sense that Chapman was right for the part.

Who was apart of the casting for the movie?
With the help of producers Alexandra Milchan and Robert Salerno, Schaefer cast Jared Leto as Mark David Chapman.