Other mistake: In the scene where Sly and his female partner are using the speed gun, a speeding car drives past. The female cop is pointing the speed gun towards the sky and not at the car, so it would never give a reading. (00:19:30)
Continuity mistake: The first scene with Murray Babitch driving across the George Washington Bridge from New York to New Jersey was actually filmed going the other direction. When driving from New York to New Jersey on the lower level of the bridge you enter a black tunnel first, and exit through a yellow tiled tunnel. The scene in the film starts in the yellow tiled tunnel - New Jersey to New York direction.
Continuity mistake: In one of the scenes, Sheriff Heflin is playing a record, and the music we hear is a song by Springsteen. However, the record doesn't have the red Columbia Records label that all of Springsteen's albums have. They obviously decided to use Springsteen's song later.
Continuity mistake: There's a scene after Superboy jumps from the bridge with a paramedic smoking a cigarette close to the butt. The camera switches and suddenly his cigarette is a freshly lit one.
Continuity mistake: In the final shootout when Freddy is shot by Leo, he falls against the car parked in the driveway and dents the passenger door. When he gets up again after Gary shoots Leo, the dent is gone.
Continuity mistake: In the final shootout at Ray's house, Figgis first fires at the crooked cops with a revolver. When he follows Freddie into the house and shoots at Ray he is shooting a semi-automatic pistol.
Suggested correction: Ray Liotta likely picked up the deceased crooked cop's Glock pistol.