A prerogative writ used to challenge the validity of a person's detention, either in official custody (e.g. when held pending deportation or extradition) or in private hands. Deriving from the royal prerogative and therefore originally obtained by petitioning the sovereign, it is now issued by the Divisional Court of the Queen's Bench Division, or, during vacation, by any High Court judge. If on an application for the writ the Court or judge is satisfied that the detention is prima facie unlawful, the custodian is ordered to appear and justify it, failing which release is ordered.
From: habeas corpus in A Dictionary of Law »