Continuity mistake: At the end of the movie, when Riggs is in the cargo area, a gunman shoots at him, he rolls and starts emptying the clip into him - you see the bullet holes in the gunman. But as Riggs is face to face with the gunman, the holes disappear.
Continuity mistake: While he's on the toilet, Murtaugh is wearing a flak jacket that disappears for one shot while he is getting instructions from the bomb squad leader. (00:54:25)
Continuity mistake: In the fight scene toward the end of the film between Riggs and the guy who killed his wife and Rika, look carefully at the watch Riggs is wearing - it moves from one arm to the other in close-up as Riggs forces the guy to stab himself. (01:38:35)
Continuity mistake: The right headlight of Murtaugh's car, when it is chasing the BMW, falls off when he hits something, but later on it is fine. (00:03:20)
Continuity mistake: Near the end of the car chase you see a shot of the station wagon Riggs and Murtaugh are riding in get held up by a couple of police cars. The hood is popped open. The shot changes to the BMW crashing into the store window and then back to the station wagon. The hood is down.
Continuity mistake: When Hans first walks into the room with the fishtank, the plastic on the floor flaps up behind him as he walks, ending up folded up on itself without much space between the man and the end of the plastic. When he gets shot and falls back onto it, it's perfectly flat and he's a lot further forward. (00:16:25)
Continuity mistake: During the opening chase when Riggs is driving through the small gap on the bridge, as Murtaugh shouts, "Get off ya mother f***er", the car that is next to them goes from being right up against their car to a good 10 feet away between the 2 shots.
Continuity mistake: When the bathroom explodes, from one angle we see the toilet come sailing out over the roof of a police truck parked at the front of the house. While the angles make it a bit tricky to judge, there's a definite leftward trajectory. We then cut to a closeup of Murtaugh's car, and the toilet lands on it as if it was flying to the right. Even if the angles are misleading, in the first shot the police truck and other cars are parked to the right of the exploding window. In the shot of Roger's car he's also parked to the right, but without all the cars visible around it which there should be. (00:57:15)
Continuity mistake: In the scene where Riggs and Rika are in the trailer while the men in the helicopters are shooting, after the scene where you see the T.V. fall down, You see the cabinet being shot. If you look carefully, you can see pieces of the cabinet fall down, then appear again. Director's cut.
Continuity mistake: During a chase scene involving Murtaugh's station wagon and a flatbed tow truck, the hotel waiter shoots at Riggs through the truck's rear window. In this series of shots, notice how Riggs is swinging by a chrome handle on the passenger's side - which wasn't there during the gunpoint hijack shot just moments ago. (00:39:30 - 00:40:45)
Continuity mistake: In the scene where Murtaugh is shooting his attackers with the nail gun the walls are apparently covered with super plastic. How is it that the plastic sheeting is light enough for the bad guy to punch through, but is able to support the weight of his corpse by a single nail when Murtaugh shoots him through the plastic? Wouldn't the plastic tear and drop the body to the floor? (01:15:45)
Continuity mistake: Near the end, when Riggs is captured by the bad guys they tie him in a straight-jacket and toss him off a pier into the drink, he's wearing a pair of Dingo style boots. Underwater when he dislocates his shoulder and escapes the straight-jacket, he sees Patsy Kendit's corpse, swims over, checks her pulse and swims to the surface. Now he's barefoot. Yet when he attacks and kills the two thugs he's got the boots on again. They can even be heard on the pavement.
Continuity mistake: After Murtaugh confirms the Alba Varden is a ship, one of Rudd's henchmen enters the house armed with a knife. Moments later when they're struggling by the hobby room's blueprint table, Murtaugh grabs the nail gun and shoots him in the forehead. Now right here, you can notice the sound of a knife being thrown to the floor as he reaches for his head. But when the henchman is up against the unhinged doors, he's once again holding a knife in his right hand. (01:21:55)