When he was filming the fight scene at the testimonial dinner, director Ulu Grosbard never informed the extras that there would be a fight. When it occurred, their reactions were genuine.
To prepare for his role as Detective Tom Spellacy, Robert Duvall went on the night beat with real-life Los Angeles area homicide detectives. Duvall also went on a stakeout, witnessed the administration of a lie detector test, and visited a real murder victim crime scene.
The movie is based on the real unsolved murder of Elizabeth Short, who was known as the Black Dahlia. This movie used facts from this case as story elements. The Black Dahlia murder case made media headlines in 1947.
This was the first film that Robert De Niro did after Raging Bull (1980). He kept some of the weight that he gained for that movie, because he felt that it better fit the character, although he still had to drop fifty-five pounds (twenty-five kilograms).