When Barney visits the witness who saw the murder and robbery, inside his apartment, the curtains of the window that opens on the alley are straight inside the apartment, but are brought up at an angle when seen from the outside.
In the opening scene, Nolan walks past a full-length glass door. Visible in reflection is a stage light with a screen in front of it with large perforations - to give the street lighting an uneven or "dappled" look.
Brewster gives out the address of the Castle Heights model home over the police radio as 466 South Camden Drive. That location is in Beverly Hills, between W. Olympic Blvd. and W. Pico Blvd. - not Castle Heights.
No such thing as a silenced revolver: At the very beginning of the movie, the bookie is shot with a snub nose revolver having a silencer attached to the barrel. Because combustion gases leak through the gap between the cylinder and the barrel (allowing a loud noise to escape), a revolver cannot be effectively silenced. Only guns with a continuous firing chamber and barrel, such as an automatic or a single shot, can be silenced.
The goof item below may give away important plot points.
The 'double bourbon' that Detective Nolan has in the bar after killing the deaf mute witness is only a single shot. But even the girl sitting next to him in the bar stays in script and refers to his 'double bourbon.'