Continuity mistake: Their car goes round the corner and the police light falls off the roof and dangles, yet is back on the roof a second later.
Continuity mistake: When Murtaugh comes downstairs and checks his tie it's on the outside of his vest. He then walks through a door and the tie is on the inside of his vest.
Continuity mistake: When Riggs is counting out of the money to pay the three drug dealers, he puts a 20 dollar note on the table. The wind then blows the note against the bag of cocaine and it is lying flat down, but in the next shot the note is folded up.
Continuity mistake: When Hunsaker is talking to Murtaugh in his house, the shadows outside dramatically change throughout the scene. First the sun is beating down on Riggs from the right (over the ocean), then from the left leaving Riggs under a bunch of shadows from the tree. This constantly changes throughout the scene.
Continuity mistake: When Riggs is working undercover at a Christmas tree lot sampling cocaine, he agrees to do business with the dealers. After one of them quotes a price, Riggs sits there looking pleasantly surprised. At this point, note how the sky behind his right shoulder is mostly overcast. Seconds later, Riggs shakes his head in agreement and reaches for his wallet - but by now mostly all of the cloud cover has vanished (as if minutes have passed by). (00:17:10)
Continuity mistake: On the shooting range, Roger hangs the target on the mechanical arm and runs it out a short distance. After it settles, the bottom hangs at about ten° to the left of the target's center. After running it back to show to his partner, and before Riggs runs it all the way to the wall, the bottom now hangs about 3 to 5° to the right of the target's center.
Continuity mistake: When Murtaugh starts questioning Alfred about the suspicious man he saw near Dixie's house, Alfred lifts up his sunglasses. Through a few questions, the glasses' ear stem rests normally behind his ear where it should (left one is visible). Suddenly Murtaugh asks about the man's hair color, but now the ear stem is hanging off. (01:09:40)