Below I have compiled a list of examples to demonstrate how this type of cut can be used:
Predator (1977) Dir: John McTiernan
J cuts and L cuts come under a technique of editing known as split editing. Split editing is referring to any type of cut in a film or video that involves a transition from one shot to another where the transition or cut of the audio and video occur at different times. This allows an edit to enhance the flow of the film it is being used in, and there are a multitude of different ways these two cuts can be implemented to produce different outcomes.
Most commonly we find this type of editing used in dialogue scenes where two characters are having a conversation. These cuts make it possible to let the characters talk normally without having to cut the image back and forth between them, which would result in a conversation that feels more like a game of ping pong. If you simply cut back and forth between two people talking the resulting clip would appear stale and boring. J and L cuts give editors an option to hold on an actor’s reaction to what they hear and introduce a different, more interesting pace to the scene.