The post-production of the film on the murderous night

To play Will Graham, William Peterson interviewed officers from the Chicago Police Department and the FBI Violence Case Unit and reviewed a large number of case files while researching the serial killer Richard. In the case of Richard Ramirez, Peterson was particularly concerned about the impact of such a heinous murder on police officers and how they differentiate between work and life. During the three years he was working on adapting the script, Michael Mann often appeared in the FBI's Behavioral Science Unit, where he met many real-life versions of Graham. Full of in-depth research, the film was hailed as the best example of cutting-edge forensic science and criminal psychology portraits at the time.

Tom Noonan, who plays the killer in the film, initially wanted to get into the role by studying serial killers, but found that this method was of no avail. He later thought of starting with the psychology of the character and learning to think that his actions were correct. , rather than harming the victim. To play the blind girl Reba McClain, Joan Allen asked representatives of the New York Association for the Blind about her true feelings. She also walked blindfolded on the streets of New York to practice the walking gait of a blind person.

When looking for candidates to play Hannibal, the producers considered John Lithgow, Mandy Patinkin, William Friedkin and Brian Dennehy. Mann selected Brian Cox on Dennehy's recommendation. When creating the character, Cox modeled himself after Peter Manuel, a Scottish serial killer with no sense of right and wrong.

In order to film the scene on the plane where Graham fell asleep while studying the crime scene photos, the crew had to use a guerrilla-style shooting method. Unable to secure a plane for filming, Mann had to book a commercial flight from Chicago to Florida for the crew. After boarding the plane, the crew immediately took out the equipment in their travel bags for filming. In order to appease the passengers and crew members, who were presented with jackets emblazoned with the film’s title.

Cinematographer Dante Spinotti makes great use of tones, such as romantic blues in scenes with Graham and his wife and subversive greens in disturbing scenes. Mann wanted to create a visual atmosphere that would lead the audience to focus on the film, thereby giving the film's story an emotional impact. When filming the climax, Mann used multiple frame rates, using multiple cameras to shoot at 24, 36, 72 and 90 frames per second.

Noonan did not allow the actors playing the victims and pursuers to see him during the filming. Those actors only knew his name was Francis. He did not take the same flight with the crew or stay in the same hotel. He was alone on set, and he and Peterson didn't meet for the first time until filming the climactic action scene. Noonan's erratic behavior created a tense atmosphere on the set as everyone began to fear him.

The gunfight scene in the film was filmed when it was being finalized. At that time, most of the crew had already left the film and there was no special effects technician to provide the blood splatter effect. The crew had to use ketchup to manually spray it. To simulate the effect of bullets flying across Francis's kitchen, Mann had the crew throw glasses, and a shard even pierced Peterson's thigh. To film the final scene where Francis is left in a pool of blood, Noonan lay in corn syrup for so long that he was nearly glued to the ground.