Continuity mistake: When Harry, dressed as an overseas pilot, enters the aeroplane during the hijack scene, one of the hijackers draws his gun right in front of Harry when he says "Good afternoon". In the next scene, the gun is further away from Harry than it was in the previous shot.
Continuity mistake: When Lt. Briggs is being interviewed after the swimming pool massacre, we see a close up of Briggs and there is a man with a moustache next to him. But when we cut to the next shot where Briggs is on television at Carol McCoy's house, the man with a moustache has suddenly disappeared.
Factual error: When the pimp murders the hooker in the taxi, he is said to have forced drain cleaner down her throat. However, he uses an aerosol can. You can even hear the metal ball shaking inside of it several times. In the 1970s, drain cleaner did come in metal cans, but what he is using is a spray can of some kind, which drain cleaner did not come in. It is always in liquid form to pour down a drain, spray would not release enough.
Revealing mistake: After the pool massacre, a police cop walks away from the scene and we see the pool with dead bodies. If you look carefully, you can see a "dead" woman in a red bikini moving her arms as if she was treading water.
Continuity mistake: After one of the cars escapes from Palancio's hideout, we get a view from the driver's seat and Harry fires a bullet into the windscreen and the car is heading directly for an office. In the next scene, the car is much further away from the office than it was in the previous shot.
Other mistake: In the scene where the mob boss gets interviewed in the garden atrium after being freed, the news media pushes up to get really close to the podium. Note that the first reporter, dressed like Gilligan, trips and almost falls into the podium. He catches himself but has to keep his head down during the rest of the shot.
Other mistake: In the beginning credits Harry says "This is the 44 magnum, the most powerful hand gun in the world" but later when he's at the range with David Soul and the other cops, when asked about his what his gun loads he says he uses .357 lite magnum.