an ancient common-law writ, issued by a court or judge directing one who holds another in his custody to produce the body of the person before the court for some specified purpose. Although there have been and are many varieties of the writ, the most important is that used to correct violations of personal liberty by directing judicial inquiry into the legality of a detention. The habeas corpus remedy is recognized in the countries of the Anglo-American legal system but is generally not found in civil-law countries, although some of the latter have adopted comparable procedures.

Many of the procedures that made for effective assertion of these rights were provided by the Habeas Corpus Act of 1679, which authorized judges to issue the writ when courts were on vacation and provided severe penalties for any judge who refused to comply with it. Its use was expanded during the 19th century to cover those held under private authority. In 1960 legislation was enacted limiting the instances in which habeas corpus could be denied and establishing new lines of appeal.

In the British colonies in North America, by the time of the American Revolution, the rights to habeas corpus were popularly regarded as among the basic protections of individual liberty. The U.S. Constitution guarantees that the privilege “shall not be suspended, unless when in cases of rebellion or invasion the public safety may require it.” In England such suspension had occurred during the wars with France at the time of the French Revolution. In the United States, Pres. Abraham Lincoln (Lincoln, Abraham) suspended the writ by executive proclamation at the outbreak of the Civil War in 1861. The presidential act was challenged by Chief Justice Roger Taney (Taney, Roger Brooke) who, in the case of Ex parte Merryman (Merryman, Ex Parte), vigorously contended that the power of suspension resided only in Congress. Lincoln ignored the order of the court, but the weight of modern opinion appears to support the view that suspension of the writ requires the consent of Congress.

The current uses of habeas corpus in the United States are quite varied. The Supreme Court's liberal interpretation of the constitutional rights of those accused of crime led in the mid-20th century to the filing of many habeas corpus petitions by prisoners, challenging their convictions. A writ frequently is requested on behalf of one in police custody for the purpose of requiring the police to either charge the arrested person with an offense or release him. Habeas corpus proceedings may be employed to obtain release of the accused prior to trial on the ground that the bail set is excessive. On occasion habeas corpus relief has been granted a prisoner who is unlawfully detained after expiration of his sentence. In cases of one arrested on a warrant of extradition, a proceeding in habeas corpus may be instituted to challenge the validity of the warrant.

The writ may also be employed in a wide variety of situations not involving criminal proceedings. Thus competing claims to the custody of a minor may be adjudicated in habeas corpus. One confined to a mental hospital may in some jurisdictions bring about his release by showing at a habeas corpus hearing that he has recovered his sanity.