After Le Parrain (1972), this was James Caan's favorite film of his own. He had stated that his monologue in the diner was the scene of which he was most proud in his career.
James Caan made sure to speak slowly and clearly and tried to avoid using contractions in his words. He decided that Frank would do this so he would save time by never having to repeat himself.
In the hospital scene, James Caan decided to stare coldly at J. Jay Saunders, who played the doctor. This really frightened Saunders, and his reaction in the scene is genuine.
The screenplay for this film was adapted from the novel "The Home Invaders", written by Frank Hohimer, a professional thief. Hohimer was serving time in prison at the time this film was in production.
James Caan remembers one night where all the cops working security on the film and "technical advisers" were hanging out together before shooting. A lot of members from both sides had grown up together or had married into each other's families. "It's just like in my neighborhood. People don't realize it's not uncommon for one brother to be a thief and another brother to be a policeman," remarks Caan. Since the statute of limitations had already been up on most of the crimes the "advisers" had committed, they would brag to the cops about how they had done it.
Michael Mann: [Cops & Robbers] Many real-life Chicago criminals and police officers served as advisors to director Michael Mann, and Mann cast many of them on screen, often in contradictory roles (former Chicago police officers Dennis Farina and Nick Nickeas appear as criminal henchmen, while former professional thief John Santucci appears as a police officer).