Continuity mistake: When the drug tester gets done with testing the heroin, he blows out the lit candle on the bottom. But when there is a far shot of him talking, the candle is still burning.
Continuity mistake: At the beginning of the film in Brooklyn, it is obviously dark outside (nighttime). As they are chasing the guy from the bar, it all of a sudden is during the daytime as it is light outside.
Suggested correction: I think that it looks dark because they are under an elevated train track.
Continuity mistake: During the car chase scene under the "B" Elevated Train in Brooklyn (86th St.), Popeye passes the same curve at least 3 or 4 times. Look closely, you'll probably see the same movie theatre over and over again. Apparently, they rerun the same chase clip to increase the length of this scene.
Factual error: The "B" train which he is chasing normally runs on the right most track (there are 3 tracks on this particular line). The middle one is never used except for out of service trains. Most of the train stations on that line service the right or left track, not the middle one.
Continuity mistake: When Popeye's being shot at by the sniper, he's hiding behind a tree and rolls towards a wall that's relatively well-lit by sunshine. The angle changes and it's now completely in shadow.
Factual error: Check out the sign over the front of the train, it should read "B", not "N". The "N" train runs on an entirely different line.
Continuity mistake: During the car crash scene, the Commanding Officer, Popeye, Detective Russo and the other cop are walking toward the accident. Close shot of Popeye, as he says, "I say we keep sitting on Boca", and they all stop walking. Immediate cut to long shot, and they are all still walking toward the accident. (01:05:41)
Continuity mistake: During the subway chase scene, Popeye's car loses about a half dozen hubcaps! The hubcaps are back in place when Popeye parks the car at the end of the chase.
Audio problem: As Popeye Doyle is chasing the elevated train, he is continually honking his car's horn to warn pedestrians and whoever else to get out of his way. One scene shows him with one hand firmly on the wheel, and he hits the top-most rim of the wheel in frustration, and the horn honks on both hits. That car did not have a rim-blow type horn mechanism - only Fords had those, and this was a Pontiac Le Mans.
Continuity mistake: At the start of the movie in France, we see an undercover French policeman shot by Pierre Nicoli, if you look quickly when the policeman is shot, we can see blood splatter all over his face. However, when we see the wider shot of him falling down his face is clean and has no blood on it at all.
Audio problem: As Popeye and Detective Russo are in the bar staking out Sal Boca, each have drinks. As they raise the glasses to their mouths, the sound of clinking ice cubes is heard. When Popeye downs his drink, the ice clinking is again heard, even though there is actually no ice in his glass.
Audio problem: When Buddy is in Sal & Angie's asking Angie Boca to model for him, their lips rarely match their words. Sometimes they appear to be saying something else, and other times it looks like they aren't speaking at all. (00:24:25)
Factual error: In the beginning of the movie when the Frenchman is shot in the face, his face is instantly a mess of blood. In reality, an entrance wound from a pistol shot is a neat little hole (i.e. blood splatters from the bullet's exit wound, not the entrance). It would take awhile for blood to cover his face. (00:03:05)
Continuity mistake: During the final shootout, Popeye chases Frenchman 1 into a building; he is wearing his hat. One shot has him without the hat.
Continuity mistake: When Popeye is tailing "Frog #1", he waits outside while the Frenchman eats a long lunch in a restaurant. At first, we see the Frenchman sitting in an interior seat, with another table of diners to his left. But by the time dessert is served, he's at a seat by the window.
Other mistake: At the very start of the chase scene, where the shooter tries to kill Popeye, he looks up to the shooter's position. There are at least 6-7 floors of the building. When Popeye looks over the edge, he can see the shooter running away from the building. In the next scene, he is chasing the shooter on foot and is not far behind him. By the time Popeye had run back down all those flights of stairs, the shooter would be long gone.
