Habeas Corpus is a writ by which a person can seek relief from wrongful detention of him or herself or some other party and it is often called by its full name, habeas corpus ad subjuciendum, in order to differentiate it from some other writs which are somewhat similar. The writ has played a very important part in the safeguarding of individual freedom against despotic action by the state or its agents. The great writ, as it is also called, is an order of a court demanding that a person who has another in his or her custody bring such a detainee before the court together with proof of the authority under which such a person has been detained in order that the court may determine the lawfulness or otherwise of the authority. If the purported authority fails the test of lawfulness, the detainee is set free forthwith.
The great writ was a development of the Common Law as developed by the English courts, and the first recorded instance of its use was in 1305, although writs which served to achieve substantially the same effect had been used as far back as the twelfth century. The explanation for the writ is that the king (or the state) is entitled to know why his subject (its citizen) has been deprived of his liberty at anytime.
The procedure, originally grounded in common law, is now regulated by statutory or constitutional provisions in most jurisdictions. Statutory intervention had become necessary in England because many early judicial rulings served to restrict the effectiveness of the remedy. In 1640, the English Parliament was obliged to pass legislation to overturn a ruling that a mere declaration that the detention, whose validity was being challenged, had been carried out at the king’s behest was a sufficient and satisfactory answer to the writ, and in 1679 the whole procedure was regularized and put on a statutory footing by the Habeas Corpus Act of that year. The value which those who were opposed to arbitrary power placed upon the great writ is underlined by the fact that the American colonists, throwing off British rule felt obliged to state in section 9, Article 1 of their new constitution that the privilege of habeas corpus shall not be suspended, unless when in cases of rebellion or invasion, the public safety may require it.
The great writ is not only available when the alleged unlawful detention is done by public officials or bodies; even where the alleged unlawful detention is done by private individuals or bodies, the writ will run. It was by way of the great writ that, in 1771, the black slave, Somersett, was declared a free man; Lord Mansfield CJ declaring that under the common law of England the concept of slavery was unknown.
Habeas Corpus is deemed a privilege, not a right; so it is liable to suspension in certain circumstances, and it has been on many occasions. The question that arises in such circumstances is whether the deprivation of the right to potential suitors is justified. In the UK, recent abridgements of the privilege have been done under statutory authority, for example, during both world wars and during the disturbances in Northern Ireland. Of course, in the UK, constitutional theory is wrapped up in the idea of the supremacy of Parliament, so that, even if the procedure were technically available to such detainees, any attempt to enforce the writ would fail since a detention done under an Act of Parliament would meet the requirement of lawfulness. However, since 1988, after the passage of the Human Rights Act, the situation has, theoretically, changed. The act of that year empowers the UK courts to overrule an Act of Parliament on the grounds that it is not compatible with the European Convention on Human Rights. But, this provision is weightier in principle than in practice; such a declaration by the court has no legal effect until, and unless, it is put into effect by the government.
In the United States as well, Habeas Corpus is not an unrestricted right, the Constitution clearly defining it as a privilege which is liable to suspension in certain circumstances and it has been suspended, or purported to be suspended, on a number of occasions, including as recently as 2006.