Habeas Corpus, in English law, is the formal commencement of several writs, issued by the superior courts, which direct a person who has another in custody to produce the body of the prisoner. Such writs are or have been used in practice for various purposes. Thus, the habeas corpus ad respondendum was used to bring up a prisoner to serve him with a writ; and the habeas corpus ad testificandum may still be used to bring up a prisoner to give evidence. But the best-known and by far the most important form of the writ is the habeas corpus ad subjiciendum, by which the person detaining another in custody is ordered to bring up his prisoner, and to state the reasons for such detention, that the court may judge of their sufficiency. This 'prerogative writ' is one of the chief securities of English liberty. By the law of England, as embodied in the Great Charter, no freeman could be imprisoned except for a crime of which he was found guilty by his peers, or for a civil debt. The effect of this rule of law was that the executive government had no right to imprison an individual on suspicion, or for an indefinite period. Arrest and imprisonment could only be justified by making a definite charge against the prisoner, and by putting him on his trial before a jury without unreasonable delay. A person illegally imprisoned could demand of the Court of King's Bench a writ of habeas corpus; and on return being made to the writ, the court might discharge the party, or admit him to bail, or send him back to await his trial, according to the nature of the case. This was the rule of law; but it need hardly be said that in despotic times the courts could not be relied on to protect the subject against illegal imprisonment. In the reign of Charles I. the judges refused to issue a habeas corpus in vacation time. They also assumed a discretionary power to grant or refuse the writ; and the government sometimes evaded the law by sending prisoners beyond the sea, to Jersey and other places. These abuses led in 1679 to the enactment of the statute 31 Car. II. chap. 2, commonly known as the Habeas Corpus Act. This act did not, as is often supposed, introduce any new form of process; but it secured to the subject the ancient constitutional remedy of which the weakness of the judges and the bad faith of the government had deprived him. The writ may be sued out by motion in court, or by an application to the Lord Chancellor or one of the judges, supported by affidavits showing that the person on whose behalf the motion or application is made is illegally detained. The chief rules of the act are as follows. When a person is committed to prison the judge to whom application is made must, unless there has been great delay in making the application, grant the writ of habeas corpus. The writ must be obeyed, more or less promptly according to the distance; but in no case must the delay exceed twenty days. Any officer who refuses the prisoner a copy of the warrant of commitment, or who shifts the prisoner to another custody without authority, forfeits £100, and for the second offence £200, and is disabled to hold office. No person once delivered by habeas corpus may be recommitted for the same offence under a penalty of £500. A person committed for treason or felony may insist on being tried in the next term or session, or admitted to bail, unless the crown witnesses cannot be ready: if not tried in the second term or session he must be discharged. Any judge who denies the writ forfeits £500. This is now the only case in which a private person may take proceedings against a judge in respect of an act done in his judicial capacity.
The Habeas Corpus Act extends only to the cases of persons imprisoned on criminal charges; but in 1816 its provisions were extended to other cases by the 56 Geo. III. chap. 100. The result of these enactments is that in all cases where any person, whether man, woman, or child, is deprived of liberty, some friend may apply for a habeas corpus directed to the officer or private person having custody of the prisoner. Refusal to make any return to the writ will of course be dealt with as contempt of court. If the party is detained by lawful authority (e.g. in the case of a child in the care of its parents, or a dangerous lunatic privately kept under restraint by his friends) the facts must be stated in the return. If the alleged authority is of a formal character (e.g. a warrant of commitment, or a certificate of lunacy) it must be produced, and the court will judge of its legal sufficiency. A writ of habeas corpus runs in any county palatine or privileged place, in the Channel Islands, and the Isle of Man. In the case of Anderson, a slave who in 1853 had escaped to Canada after killing a Missouri planter, it was held that the writ might be applied for by a person confined in a colony; but an act passed in 1862 provides that the writ shall not run in any colony where there is a court having authority to grant a habeas corpus.
The law of habeas corpus does not extend to Scotland; but the subject is protected by the Wrongous Imprisonment Act, 1701, chap. 6, which is often called the Scotch Habeas Corpus Act. In Ireland there was no Habeas Corpus Act until 1783; and the provisions of the law then passed have frequently been suspended by acts arming the government with exceptional powers. The protection of habeas corpus is secured to American citizens by the constitution of the United States, and by the constitution of most of the states. The state courts do not discharge persons imprisoned by order of federal courts; nor will the federal courts interfere with persons imprisoned under state process.
In times of rebellion or disturbance the government may find it necessary to arrest dangerous persons, and to detain them in custody without bringing them to trial. In such cases the government may either break the law and apply to parliament for an Act of Indemnity, or it may invite parliament to suspend the Habeas Corpus Act for a time. In 1881, for example, the Irish government was empowered to detain without trial all persons reasonably suspected of complicity in treason and crime. In the United States, Merryman's case, in 1867, gave rise to a keen discussion, some eminent lawyers maintaining that the president, of his own authority, could suspend the law of habeas corpus, others contending that the power of suspension could only be exercised by congress. For the history and law of Habeas Corpus, see Blackstone's Commentaries, Hallam's Constitutional History, Story's Commentaries on the Constitution of the United States, &c.