During the scene when Jake plays cards with the Latino gangsters, director Antoine Fuqua gave certain instructions to the actors playing the gangsters, without telling Ethan Hawke. This was done to further confuse him and add to the tension of the scene.
T. Rodgers, the founder of the Black P. Stones Bloods in Baldwin Village a.k.a. The Jungles in Los Angeles, was on set for all of the filming in his neighborhood and allowed the producers to use his neighborhood in exchange for casting gang members.
When the movie came out, many viewers and critics were skeptical of the scenes where Jake Hoyt smokes marijuana laced with PCP and Alonzo's explanation of how a cop who didn't take drugs offered to him on the street would be ID'd as police and murdered. David Ayer responded in an interview by holding up a highlighted section of the LAPD's rules and regulations; it stated that officers were allowed to use narcotics in very specific undercover situations, and hewed closely to what Alonzo told Jake.
Tobey Maguire was seriously considered for the part of Officer Jake Hoyt. He even followed Undercover Narcotics officers in Los Angeles for two months and gained weight for the role. He was dropped when Ethan Hawke, Fuqua's first choice, was finally available for the shooting schedule.
Before Antoine Fuqua was involved in the project, Davis Guggenheim was set to direct with Samuel L. Jackson as Detective-Sergeant Alonzo Harris and Matt Damon as rookie Officer Jake Hoyt. When Denzel Washington accepted the role as Detective-Sergeant Alonzo Harris, Guggenheim was replaced per his request. Samuel L. Jackson would later voice the character Officer Frank Tenpenny in Grand Theft Auto: San Andreas and based him on Rafael Perez.
The film had several police technical advisors. Among them is Detective-Sergeant Brian Davis, an LAPD veteran who is one of the most respected and decorated officer of the infamous elite Special Investigation Section.
Eminem was offered to play Rookie cop Jake Hoyt. The rapper turned it down, due to the development of 8 Mile (2002) and had to stay available for that. Had he accepted the role, he would've shared scenes with rappers, Snoop Dogg and Dr. Dre, the latter of which is Eminem's mentor. Instead, Ethan Hawke took the part and was nominated for the Academy Award for Best Supporting Actor. Eminem was nominated and won the following year for 8 Mile (2002), but for the Academy Award for Best Original Song Lose Yourself.
David Ayer wrote the first draft in 1995, way before the Rampart Scandal made headlines in 1998. In the first draft, Alonzo was a Latino officer in charge of drug enforcement in the gang infested area of Pico-Union within the Rampart Division. He was a loner and didn't have any partner because of his reputation as a corrupt and racist cop. But the basics elements of the character were there: he wears expensive jewelry and drives a 1979 Monte Carlo model.
Alonzo's car is a 1979 Chevy Monte Carlo, with some modifications: it has Dayton wire wheels with bullet caps; a Grant steering wheel; Flowmaster exhaust; and hydraulics. Added to this, the car is outfitted with a sunroof, which that era's Monte Carlos never had.
Alonzo's weapons of choice in the film are the venerable Smith & Wesson 4506, of which he carries two in a dual shoulder holster. The 4506 is a .45 ACP semi automatic [previously] used by many police departments around the country.
The whiskey Roger offers to Alonzo and Jake is a vintage of the Macallan. Alonzo mentions it as "$300 dollars a glass." Whether or not this is an exaggeration, the whiskey is sure to be on the finer side. Given its light shade and the white label, it could well be Macallan 30-year-old, which sells for an average of $2,500 per bottle.
Although not shown in the film, the producers of the movie asked if the Angelus Temple cross, a famous Echo Park landmark could be used in the film. When the church declined, they brought in a "fake" cross and using a crane hoisted it up a few feet in front of the real Angelus Temple.
Director Antoine Fuqua says the production was a very intense period of his life. The locations in South Central Los Angeles included some gang infested neighborhoods and Fuqua also went through some personal grief in the middle of shooting the film. After the film was released, Fuqua needed to step away from it and he didn't do much publicity. He attended the 58th Venice International Film Festival where the film premiered out of competition in 2001.
At the Academy Awards most directors usually sit close to the actors, but at The 74th Annual Academy Awards (2002) director Antoine Fuqua was seated a few rows back from actor Denzel Washington. During his acceptance speech even Washington didn't know where Fuqua was sitting, so he said "a brilliant young African American filmmaker, I don't know where you are Antoine, love you".
During the movie, Hoyt often does the opposite of what Alonzo tells him to do. He tells Hoyt not to get involved with anything but organized crime and avoid wasting time with small crimes but he helps the girl who is getting raped (which eventually saves his life), he tells him never to mention his family while working but he says he's married and has a daughter when he's about to be shot in the tub, he tells Hoyt never to enter the rough neighborhood "Jungles" without him but he does (which eventually helps him catch Alonzo).
The original ending of the script was Hoyt crashing the pad of Alonzo's girlfriend and find his training officer in the middle of an orgy with two young women. Hoyt shows him the money that Smiley was supposed to deliver to the Russians and tells him that there is a crew of hit men looking all over for him. Alonzo then commits suicide in front of Hoyt.
Some weaponry used in the film includes: Two Smith and Wesson 4506s carried by Alonzo, Berreta 92FS (used by Jake Hoyt), Glock 17 (one of the backup guns carried by Alonzo), M1911 pistol (used by Alonzo and Hoyt during the confrontation in Imperial Courts) Mossberg 500 (used to shoot Roger), sawed off Remington 870 (used by Alonzo when shooting at Jake) and Glock 19 (used by crippled drug dealer Blue as well as Officer Paul). Many of these weapons are LAPD issue which lends to the credibility of the film and shows that the production team did its research.
While getting in his car after police have talked with him about Roger's death, Alonzo can be heard saying "Just keep that tub clean okay," over the phone. This line foreshadows the tub scene between Jake and the Mexican gangsters and Alonzo's betrayal by setting Jake up to be killed by them.
The speech "An L.A.P.D. narcotics officer was killed today serving a high risk warrant. A spokesperson said the officer is survived buy his wife and infant child." Is said twice in the movie. Alonzo says it first while threatening Jake's life with a shotgun after he had just shot Roger (failing to get Jake to pull the trigger). It is said again at the end of the movie reporting over about Alonzo's death.