An alibi is a defense used in legal contexts to prove that a person was not present at the scene of a crime when it occurred. It typically involves providing evidence or testimony that confirms the individual's location elsewhere, making it impossible for them to have committed the alleged act. In criminal cases, an alibi can be supported by various forms of evidence, such as witness statements, video footage, or receipts. Establishing a credible alibi can significantly impact the outcome of a trial, as it may lead to the exoneration of the accused if proven valid.