Deliberate mistake: At the end of the film, two officers attempt to surround and handcuff Joshua. Using two officers to cuff someone is NEVER done for the exact reason of what ends up happening, as Joshua manages to grab a gun from one of the officers. Only one officer would have been doing the deed in the real world, but it's clear this error in being completely against police protocol had to happen so the good guys could prevail over the villain.
Lethal Weapon (1987)
1 deliberate mistake
Directed by: Richard Donner
Starring: Mel Gibson, Danny Glover, Gary Busey, Mitch Ryan, Tom Atkins
Revealing mistake: Riggs handcuffs himself to the depressed businessman. They jump off the building but they're not handcuffed to each other anymore. They used plastic cuffs which could separate during the stunt in case anything went wrong. They break just as they jump, so they grab each other's hands to stay in contact. After they land the cuffs are attached again. (00:31:00)
Roger Murtaugh: See how easy that was? Boom, still alive. Now we question him. You know why we question him? Because I got him in the leg. I didn't shoot him full of holes or try to jump off a building with him.
Martin Riggs: Hey, that's no fair. The building guy lived.
Trivia: During the scene in which we see Murtaugh talking to Hunsaker about his involvement with the Drug dealers. Hunsaker mentions 'Air America', a CIA front during Vietnam. Air America was a film regarding this very thing, starring Mel Gibson and filmed three years after Lethal Weapon.
Question: In the nightclub, Mel Gibson shoots a guy who says "Hey, what are you..." Was he a bad guy, or was he just a random citizen?
Chosen answer: He was one of Hunsacker's men.