Factual error: If you pay attention to the backgrounds of the scene where Frank is in the airport and when Frank is being arrested as he walks from the church, you can see two cars pass by which weren't produced until at least 2000.
Factual error: In a shot in Harlem, a Ford Econoline AVIS rental truck drives on the adjacent street. The specific Econoline van was at least a mid-90's to 2000+ model van and the movie takes place in the 70s.
Continuity mistake: When Russell Crowe and the other cop are chasing a crook through a hotel room, Crowe gets pinched in a doorway by the crook with the door. The crook starts to bite Crowe's hand, so Crowe signals the other cop to smash the crook's head through the door with a mallet. When the cop does, he uses the handle end, and in the next shot, when he's pulling the mallet out back through the door, it's coming out with the hammer-head end first.
Continuity mistake: In the opening scene, just after the man is set afire he falls to the ground. Frank shoots him and while firing his weapon jams. A casing is stuck in the ejection port (called a stovepipe when it happens). After the round sticks he continues to pull the trigger and the weapon continues to fire.
Factual error: The camera pans from the opening of the subway tunnel to Lucas' street corner, which is shown to be on the intersection of 116th Street and 8th Avenue (in green with white lettering). This is impossible, as the Manhattan Valley Viaduct, which carries the IRT Broadway-7th Avenue Line, spans from 122nd to 135th streets, and does not do so on 8th Avenue. While there is a subway line under 8th Avenue by 116th Street (IND 8th Avenue Line), it is all underground and no such opening exists. Also, the viaduct closes several blocks north of 116th street, therefore you should not see any tracks. The corner that you see is actually W 135th Street and Broadway, as the viaduct exists only on Broadway in Manhattan. Also, the signs are green with white lettering. This was not so in the 60s-70s, as in the entire borough of Manhattan during this period, street signs were yellow with black lettering.
Factual error: When Frank goes in the Chinese place to get the car keys from his driver, he looks up the street and sees a car turning onto another street. The car looks to be a late 80s to early 90s SUV, probably a Dodge Durango, judging by the headlights and foglights.
Factual error: When a character is on a pay phone, in the background there is a sedan and two full-size vans that are from the 90s decade, not when the movie is set.
Factual error: In the movie one of the members of the new drug squad has a Wu-Tang Clan Tattoo on his left shoulder. (He is played by RZA of the Wu-Tang Clan). The Wu-Tang Clan was not up and running until 1993.
Visible crew/equipment: About an hour and 12 minutes into the film, Russel Crowe is chasing the guy in the Bronco. After he gets to where he is going, he stops by the window of a building and watches some men enter. The camera changes to his point of view and pans to the left. As it is doing so, its reflection becomes visible in the glass.
Factual error: The C-130 Herc transporting the dope makes a turn towards the camera. Clearly visible on the left of the screen is a C-17 Globemaster, which was not introduced until 14th July 1993 twenty years after the scene is set.
Factual error: When Russell Crowe's character is standing by his car at the end, waiting to arrest Denzel, Denzel notices there are cop cars on either side of the block. When it goes to the shot of the cop cars on his right, a modern day sedan that is tan in color passes right by the cop cars. The problem is, this film is set in the 1970s.
Factual error: In law school, Richie Roberts is asked to take the prosecution's side on US vs Mead. The actual case, United States v. Mead Corp. was not argued in the Supreme Court until November 2000.