Continuity mistake: After Ajax is arrested Swan goes to the station with "tough chick", the first time you see the train platform it's empty but a few seconds later a man has appeared from nowhere, then a policeman sees Swan and chases him and the man has once again vanished. (00:55:25)
Visible crew/equipment: In the final scene before Phil Daniels rides the scooter off the cliff you can see a shadow of the helicopter filming the scene.
Factual error: In the opening scene that shows San Francisco scenery there is a shot of a large TV tower called Sutro Tower. The film takes place in 1960 and Sutro Tower wasn't built until 1973.
Factual error: All Borstal inmates were subject to the same mandatory haircut of short back and sides, yet many types of hairstyles are shown in the film.
Continuity mistake: During the time when Vince and Sheldon are on the highway, in the cab fleeing the bad guys in Tijada , the same cars can be seen over and over again between shots.
Continuity mistake: When Watson is conned by the prostitute who says she knows Mary Kelly, she lures him into a closed alley. After Watson has called the police and subdued the attacker, 2 constables arrive and arrest Watson, but as they all leave, a third constable comes from behind the camera. Either he magically appeared, or he walked through the wall behind.
Other mistake: The Onion Field is a true story about a cop who who is murdered on March 9, 1963. In the film prior to the murder one of the suspects is shown watching General Hospital on TV. GH didn't debut until April 1 1963, that almost a month after the murder happened. (00:20:55)
Continuity mistake: Kindaichi follows the gang of rollerskating thieves in their hideout. The female leader says she has a question about his book, and hands him what he identifies as his book of short stories. He's holding it with the left hand in close-up, but in the next shot it's the right hand. (00:17:40)