Use the adjective exonerated to describe someone who's been proven innocent. A boy whose mother thinks he stole a bag of candy is exonerated when his teacher explains that he won the candy in a spelling contest.
When a suspect is let off the hook, or freed from guilt, he is exonerated. A prisoner set free after his lawyer presents new evidence is exonerated of his crime, and a basketball player might be exonerated of a foul accusation once the referees examine a video tape of the game. Exonerated comes from the Latin word for "remove a burden or unload," exoneratus. When the burden of guilt is removed from you, you're exonerated.