Character mistake: The "MAC-10" machine pistol used by Darryl and Sergeant Murtough is actually a Cobray M11/9.
Other mistake: When Cole is looking at the LAPD records, Billy Phelps has a birth-date of 9/16/63 and is listed as 28 years old, meaning the current date is at least 9/16/91. However, the first record, Rick Sabman, has a birth-date of 9/1/60 and is only listed as 30 years old, when he should be 31.
Continuity mistake: When Riggs and Murtaugh are disarming the bomb in the car at the start of the movie, the sweat on Murtaugh's face keeps disappearing and re-appearing between shots.
Continuity mistake: During the chase involving the road-rail truck, the truck used by the villains is diesel powered, as evidenced by the "DIESEL" decal below the left headlight, seen while the truck is still on rails. However, later on when the truck is on surface roads, the below-headlight decal has changed to "EFI", indicating it is now a gas-powered truck.
Other mistake: In the scene where 'Sergeant' Jack Travis is asking to see billy Phelps, he is addressed as a Sergeant, later when Lorna is showing the CCTV footage from the interrogation room, she calls him Lieutenant Jack Travis. Is he a sergeant or a lieutenant? Furthermore, given he is a former police officer, he wouldn't be allowed near the station, let alone be allowed to interrogate a suspect in police custody.
Other mistake: After the shootout, where Rog kills his son's friend, Rog turns the kid's body over. He pulls his sunglasses off. The kid, who is supposedly dead, moves his eyes.
Visible crew/equipment: When Leo pulls up with the folks looking at Murtagh's house, film lights are reflected in both vehicles. They look very out of place.
Visible crew/equipment: When Riggs and Murtaugh go to see Billy, who has just been murdered, the camera and its operator are reflected in the interrogation room door.
Other mistake: Murtaugh is in the bathtub in the end and his kids rush in to celebrate his retirement. He's supposedly naked. Later, he pulls his wife in with him and you can tell he is wearing black underwear.
Other mistake: At the construction site, when the car rolls in empty. Not only is the windshield suddenly tinted, the car is also riddled with about 100 bullet-holes when only 1 or 2 guys fired a few bursts.
Continuity mistake: Just before the end, Riggs and Murtaugh argue in the street. In the background is a cloud of dust and a greenish car driving around. This same car drives the same piece of road 5 seconds later, and another 10 seconds later you hear the same engine/exhaust sound during a close-up (4 passes total if you count the first dust cloud).
Continuity mistake: When Riggs and Sergeant Cole are showing battle wounds at her house, Riggs pulls his pants down to show her the knife wound in his leg from Lethal weapon 2. He is showing her his left leg with a scar on it but it was his right leg that got stabbed.
Suggested correction: He shows his right leg (the correct leg).
Visible crew/equipment: As Riggs and Murtaugh start shooting at the construction site, a shadow of camera equipment can be seen on the pile of wood they are hiding behind.
Continuity mistake: When the armor truck driving thief starts to come to on the hood, he lifts his head straight up. But in the next shot his head is back down and tilted and he lifts it up again.
Visible crew/equipment: Leo pulls up to the construction site and gets out of his vehicle. During this entire sequence, you can see a very obvious film light with a diffuser reflected in the driver's side of his red car.
Visible crew/equipment: Leo is arguing with Riggs and Murtaugh at the construction site about shooting out his tires. The camera pans over to see them leaving in their cruiser. The camera crew's feet can be seen in the bumper.
Continuity mistake: After the end credits roll there is a brief scene similar to the opening, with a building being blown up. Riggs and Murtaugh back out of the area just as the explosion starts and completely leave. There is a high angle shot and a police car appears where they just were. It wasn't there before.
Visible crew/equipment: The first angle of the building exploding is from high up, looking down on the scene. There is a visible crane with a camera on it in the bottom left of this brief angle.
Visible crew/equipment: Right after Riggs saves Rianne's job, he and Murtaugh are driving in Rigg's vehicle. There is a shot looking through the driver's side window. Pay close attention to the reflection the truck makes in the glass on the buildings, you can see the crew and at least two cameras shooting the shot from a rig.
Other mistake: The end credits mis-spell St. Petersburg as "St. Petersberg".
