An alibi (from the Latin, alibī, meaning "somewhere else") is a statement by a person, who is a possible perpetrator of a crime, of where they were at the time a particular offence was committed, which is somewhere other than where the crime took place. During a police investigation, all possible suspects are usually asked to provide details of their whereabouts during the relevant time period, which where possible would usually be confirmed by other persons or in other ways (such as by checking phone records, or credit card receipts, use of CCTV, etc.).

During a criminal trial, an alibi is a defence raised by the accused as proof that they could not have committed the crime because they were in some other place at the time the alleged offence was committed. The Criminal Law Deskbook of Criminal Procedure states: "Alibi is different from all of the other defences; it is based upon the premise that the defendant is truly innocent."

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