Continuity mistake: When Hunsaker's shot, his eggnog gets all over his tie and shirt. When the camera angle cuts to Murtaugh's reaction, Hunsaker's shirt and tie are clean and there is no eggnog pouring from the container. Also there is no hole of any kind in the glass door behind him in which the bullet made.
Continuity mistake: The Christmas illumination on the balcony of Amanda Hunsaker's hotel room is arranged in three different ways: In the first shot, before she takes drugs, it is attached to the side of the railing. When she steps out, the lights are hanging about 10 inches below the railing, like they are later when Murtaugh searches her room. And when she climbs up to jump the bulbs are directly hanging down from the railing.
Continuity mistake: As Riggs exits the car, he takes the cigarette out of his mouth. The camera angle chages to show him standing outside the car, handling his pistol, and the cigarette is back in his mouth, with no time to put it there and the audio indicates the shots are consecutive time.
Continuity mistake: While working out the case at the shooting range, Murtaugh only fires one shot, and Riggs fires 9 (offscreen shots during their continuous conversation are noticeably quieter, from other shooters). When they reel in the targets, Murtaugh's target has 6 holes, and Riggs' has 14 or 15.
Continuity mistake: When coked-up Amanda first looks down from the balcony, we see the ground from her vantage point. Were she to jump from this location, she would land on the huge awning below (the curved dark area). If she put real effort into jumping forward to clear the awning (and she didn't), she'd land just to the right of the lighted sidewalk, onto the grass. And if she were an olympic long-jumper and not high on cocaine, she might have landed on the red or black car parked at the curb. Under no circumstances could she have landed on the gray car, well to her left - yet she does.
Continuity mistake: In the scene where Riggs is chasing Joshua and is told by Murtagh to take a shortcut to catch Joshua, he is shown running in bare feet. After shooting at Joshua from on top of the freeway he then runs down the embankment and is shown wearing tennis shoes, but there is nowhere these shoes could have come from and he is never shown putting them on.
Continuity mistake: When Riggs sees the car with Mr. Joshua coming he pushes the hooker away and starts running, but when he is shot at it looks as if he was standing with his back to a shop window. Accordingly, his bullet-proof vest has holes in the front, but then his red jacket has only holes in the back.
Continuity mistake: Director's cut (or extra scenes on Lethal Weapon 4 DVD): When Riggs is sitting there at the beginning of the movie, he is crying and looking at the picture of his wife on the right and wedding day on the left. Earlier in the movie when the picture was setting on the TV set his wife's picture was on the left and his wedding day picture was on the right. Not only that, but in at the start the pictures are in a folding frame. During the near-suicide scene they are not. [The first scene shows Riggs has damaged the frame, and says to the photo of his wife, "I'll buy you a new one." which explains the later changes.]
Continuity mistake: In the scene just after the jumper, Murtaugh pulls Riggs into a room and asks Riggs if he wants to die. He hands Riggs his pistol. When Riggs puts the pistol to his temple you can see and hear him cocking the hammer. After some arguing about the positioning of the gun, Riggs then puts the barrel unter his chin. While he's pulling the trigger the camera goes to a close-up of the pistol and shows the hammer pulling back, as he squeezes the trigger.
Continuity mistake: When Riggs is talking to Mr. Joshua before the electrical shock treatment starts, every time the camera shows a side shot the water is covering his head and face, but every time the camera angle changes to the front he is completely dry and the water is in the background nowhere near him.
Continuity mistake: After Murtaugh teams up with Riggs they walk through a parking garage. A police car drives by them twice (at walking speed, with its lights on - in the garage), first in a closer, then in a wider shot, while the dialogue continues, ruling out any artistic intention of this repetition.
Continuity mistake: Towards the end of the meeting between the General and Mendez, Mendez steps backwards and bumps into one of the General's men. He turns around and makes some jerky moves with both arms. The camera cuts to the General, and we see Mendez in the background colliding with the other guy once again in exactly the same way as before.
Continuity mistake: When Amanda is first shown lying in bed, she is wearing her left shoe, but not the right. When she steps up onto the railing, the shoe is on her right foot, but this looks to be a mirror image, possibly on the sliding glass door - fair enough. But when she's lying on the roof of the car, she's wearing both shoes.
Continuity mistake: When Riggs and Murtaugh are driving to the house in Beverly Hills to shoot the guy in the pool, Riggs is lighting a cigarette and then Murtaugh says "You're not gonna smoke in the car." Riggs answers "Yes, but I'm gonna roll down the window." In the previous shot you can see that the window is already rolled down.
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 the helicopter with Joshua comes up and he starts firing at the house, Hunsaker has both hands on the carton of eggnog. When the camera cuts to a wide shot, he's starting to react to being shot again, and his left hand is about a foot away from the carton.
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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).
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.
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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.