The development of English Common Law relied on the courts to issue writs that allowed persons to proceed with a legal action. Over time the courts also used writs to direct other courts, sheriffs, and attorneys to perform certain actions. In modern law, courts primarily use writs to grant extraordinary relief, to grant the right of appeal, or to grant the sheriff authority to seize property. Most other common-law writs were discarded in U.S. law, as the courts moved to simpler and more general methods of starting civil actions.
U.S. courts commonly use several extraordinary writs, which are issued only when the courts believe that usual remedies have failed. The writ of Habeas Corpus, sometimes called the “great writ,” is probably the best-known example of a writ. A writ of habeas corpus is a legal document ordering anyone who is officially holding the petitioner (the person requesting the writ) to bring him into court to determine whether the detention is unlawful. A federal court can hear an application for a writ of habeas corpus by a state prisoner who is being held in custody, allegedly in violation of the U.S. Constitution or the laws of the United States.