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.
When Brewster goes to Sternmueller's apartment, from the exterior shot the black window blind is closed. In the next, interior shot, it is half open.
In the beginning of the film, when the police have been called to the scene of the shooting, a traveling shot of a responding police car shows a black and white car--no lettering saying "Police", or a city logo, or badge, or anything; just a plain black and white four-door sedan. However, when it pulls into the alley next to the crime scene and the driver gets out, the word "POLICE" in large black lettering can be seen on the door.
When Patty and Barney enter the model house, the ceiling of the one-story house is much higher than the height of the house seen from outside.
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.
At the very start of the movie Chandler attaches a silencer onto a gun by pushing it into the revolver. It would have been screwed in or it would pop out by the force of a gunshot. Following this, he holds the gun by the silencer which would be white hot if he actually shot a bullet out of it.
About 5 seconds into the opening tracking shot of "Detective Nolan" striding down the sidewalk, the shadow of the camera dolly is seen on the wall behind him.
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.
At the beginning of the movie, as Nolan pulls his first victim into the alley, the shadow of the boom mic is clearly visible on the wall behind them.
When Nolan wipes his fingerprints from the dead man's apartment, he overlooks the pencil he'd picked up.
When Patty takes off her pajamas and gets dressed, she is shown with bare shoulders in a shot that ends slightly lower. Then she puts on a shirt and starts buttoning it. No way a woman in 1954 would wear a thin shirt with nothing under it.