Scenes of Adrien Brody sobbing in the body drawer were real. Brody had asked director John Maybury to keep him locked in even when they weren't filming so he could get the feel of the character's despair. Eventually, Brody lost it during filming and Maybury caught it on tape.
The Jacket is based on the story "The Star Rover" by Jack London which in turn was based on his interviews with Ed Morrell, who whilst in prison at San Quentin was tortured, often with a very tight straitjacket which constricted his chest, breathing and blood flow. In order to cope with this he quickly learned self-hypnosis similar to what Jack Starks goes through.
During the opening credits there is video and audio of army footage. Some of this is footage of an actual U.S. Apache helicopter night engagement in Iraq, in which the U.S. military attacks and kills several insurgents. This footage can be viewed on Youtube.
The scenes in the mental hospital were shot in the former Bangour Village Hospital, a disused insane asylum, in West Lothian, Scotland, near Edinburgh. As The Jacket was released, several other film scouts expressed an interest in the hospital building as a location, but the area had already been earmarked for housing development. Since then, the housing development has been scrapped, and Bangour Village Hospital still stands as it did at the time of filming, and continues to attract ghost-hunters as certain of the patient villas are believed to be haunted.
During filming of the key flashback scene, where Angelo Andreo playing Babak the Iraqi Boy shoots Adrien Brody in the head, the boy is actually aiming at one of the extras, Tom Burke, who played the Humvee gunner. Adrian Brody, realizing he wouldn't actually be on camera for that shot had escaped to his trailer for a break.