During the fight in the records room of the police station, Bud White inflicts several bruises to the right side of Exley's face. In the very next scene, Exley's face is clear, but when he shows up at Lynn Bracken's home, his face is bruised and discolored again.
During the shot of when Bud White's vehicle arrives at Pierce Patchett's house, there is a JUMP-CUT where several frames have been removed. This is noticeable just before Bud opens his car door, the trees in the background appear to suddenly skip in motion.
At the start, just after Ed Exley is interviewed, Edmund Exley and Dudley Smith walk down the stairs of the police station where Dudley picks up two drinks. He hands one to Ed and the other for himself. When Dudley walks away, his has disappeared.
When Bud White drives up to the Victory Motel for the interrogation of Sid Hudgens, it is raining heavily and the sky is gray and overcast. But in the brief shot of Bud running through the doorway, the parking lot in the background is bathed in bright sunshine.
Bud White smashes Ellis Loew's face into his bathroom mirror twice, with the sound of glass breaking. However, the mirror is completely intact.
During the fight between the cops and the Mexicans, the newspaper photographer raises his camera to take a photo. When he does so, the flashbulb fires. However, the resulting photo was obviously not taken with a flash. If it was, the officers in the foreground would have been overexposed and the rest of the scene would have looked more as though it were lit from the front, rather than from the sides and above.
In the middle of the climactic shoot-out, Exley fires at least 7 shots from the snub-nosed revolver without reloading. The gun shown holds only 6.
As Bud White views Sid Hudgens' body in Hudgens' office, a uniformed policeman addresses him as "Sergeant." Bud White was a plain clothes Detective, but did not hold the rank of sergeant.
In the early drug bust scene with Vincennes and Sid, a 1950 Ford police car is sitting in the parking lot of the bust house. It has 1956 Ford hubcaps, which would not have been factually correct on a 1950 Ford, much less a movie from 1953.
The newspaper headline for "Bloody Christmas" is dated soon after the incident. In fact, Bill Parker and the LAPD covered it up for months before press coverage forced them to acknowledge it,
The phone number of Fleur-de-Lis is CRestview 2239. At the time, Los Angeles was using a mixture of phone numbers with 4 and 5 digits after the exchange (what today would be called 6 and 7 digit phone numbers).
White leaves Lynn's house when it is raining. It is still raining when he fights with Exley in the records room, yet when they confront the District Attorney, it is clear outside with scant evidence of rain having fallen. However, these locations are far enough apart that this is possible. In addition, there are rain streaks and tire tracks that imply the rain had fallen there earlier.
When Ed Exley asks Lynn Bracken what she can tell him about Dudley Smith, she says she has never heard of him. While unlikely to be true, she was quite possibly lying.
When Exley blasts one of the rapists out of the window, an enormous belt can be seen around the man's waist (to yank him backwards).
White's car leaves dust clouds when he leaves the Victory Motel on the way to Lynn's house during the rain storm.
Susan Lefferts is dead, yet her eyelids move as she is being shown for identification by her mother.
When two of Mickey Cohen's henchmen are gunned down in their car (right after the scene where Bud White gets his badge and gun back from Dudley), the outline of an explosive squib can be seen on each actor's forehead before the gunfire begins.
Near the end of the motel shoot-out, a goon with a shotgun is closing in on Exley until Bud White shoots him from under the floorboards. He is shot in the chest and the squib under the actor's shirt causes his tie to fly up into his face, which wouldn't happen if not for the outward force of the squib.
In the Nite Owl café murder scene, as the camera pans over the café, the mustard and ketchup are seen to be in plastic containers. In the 1950s, mustard and ketchup always came in glass bottles.
There is a large vase of Stargazer lilies in Pierce Patchett's living room. The story takes place in 1953. Stargazer lilies were not created until 1974.
In the scenes showing the pot bust, the marijuana is shown in a plastic baggie which did not exist in 1953.
The sign at the Victory Motel indicates each room has a television. This is highly unlikely given the time the story takes place. Televisions were still rare, especially in a motel that was already closed in 1952.
In the street scene after the kidnapped girl is rescued, a blue U.S. Postal Service box is visible. Mailboxes were painted olive drab until the color scheme was changed to red, white and blue on July 4, 1955. The U.S. Postal Service did not exist until 1971, when it replaced the U.S. Post Office Department. Prior to 1971, equipment, including trucks and mail boxes, were labeled "U.S. Mail."
When White meets Dudley for a drink, he asks, "Well Captain, what do you want?", although he is mouthing something else.
The scene outside the liquor store where Bud White confronts Leland "Buzz" Meeks ends with White unloading a revolver he had earlier confiscated from Meeks. He spins the cylinder off-camera, heard as a distinctive series of rapid clicks. However, only old style single-action revolvers - the type seen in westerns - make this sound when their cylinders are spun. This gun is shown to have a swing-out cylinder, which makes no sound when spun like this, since the cylinder is disconnected from the lockwork while swung out.
When Dudley breaks up a fight between White and Exley, he tells Exley not to bother White when his blood is up, although he is mouthing something else.
When Sid Hudgens is talking to Jack Vincennes about the male hooker, his words don't match his lips.
When the D.A. is talking to Bud White in his bathroom in front of the mirror, at one point, his lips don't match what is heard.
In one shot, when Bud White is dangling the D.A. out the window, the actor's safety cable is visible.
After the Night Owl suspects have escaped, Exley has an idea where they might be hiding and asks the police stenographer about the notes on the interrogation where one of the men confessed that they get their drugs from "Roland Naverette. He has a hold-up on Bunker Hill and sells Red Devils." However, neither in the suspect's statement nor the stenographer's transcription is an address specified. Bunker Hill in Los Angeles is not a street but a neighborhood. Yet Exley is able to grab Officer Carlyle and go straight to the apartment without the benefit of a specific street address.
Despite all the noise and commotion made when Bud White is dangling the D.A. out his office window, the District Attorney's conscientious secretary never once comes in to ask what's going on, nor does she call for help.
When Mrs. Lefferts identifies her dead daughter under the sheet on the M.E.'s cold metal gurney, the girl's eyes twitch beneath her closed lids.
Just before the big shoot-out, White throws Exley a magazine of ammo for his pistol, but he calls it a clip. Even though the terms are often used interchangeably, a magazine is not a clip.
When Bud White finds out his ex-partner Dick Stensland was killed, he goes to the morgue, when Bud lifts the sheet, uncovering Stensland's dead body, his eye is seen moving briefly under his eyelid.