A more thorough explanation:

The criminal-instrumentality rule is a principle that states that when a criminal act is committed, the act itself will be considered the proximate cause of the crime, rather than any negligence on the part of the victim that may have made the crime possible.

For example, if someone leaves their car unlocked and it is stolen, the thief is still responsible for the crime of theft, even though the victim's negligence made it easier for the thief to commit the crime. The criminal-instrumentality rule ensures that the thief cannot use the victim's negligence as a defense.

Another example would be if someone leaves a ladder leaning against their house and a burglar uses it to climb in through a window. The burglar is still responsible for the crime of burglary, even though the victim's negligence in leaving the ladder out made it easier for the burglar to commit the crime.

The criminal-instrumentality rule is important because it ensures that criminals are held responsible for their actions, regardless of any negligence on the part of the victim. It also helps to deter criminal behavior by making it clear that criminals cannot use the victim's negligence as an excuse for their actions.