proof

N. (usually uncountable) a fact or piece of information which shows that something exists or is true

In the United States, you have to show proof of your age to be able to drink alcohol in a bar.

A guilty verdict on the charge of violating the Archaeological Resources Protection Act would have required proof that the men knew or should have known that the petroglyphs were valuable artifacts.

see evidence

to prove

N. to show that something is true