Alibi

The plea or mode of defense under which a person on trial for a crime proves or attempts to prove that he was in another place when the alleged act was committed; as, to set up an alibi; to prove an alibi.

Evidence showing that a person was elsewhere when a crime occurred.

exonerate by means of an alibi

(law) a defense by an accused person purporting to show that they could not have committed the crime in question