Habeas Corpus is a writ by which the personal liberty of the subject can be enforced. By the Petition of Right (3 Charles I.) it is expressly declared that no freeman shall be imprisoned or detained without cause shown, to which he may make answer according to law, and by the 16th Charles I. c. 10 it was enacted that if any person should be restrained of his liberty by order or decree of an illegal court, or by command of the King's Majesty in person, or by warrant of the Council Board or of any of the Privy Council, he should, upon demand of his counsel, have a writ of habeas corpus to bring his body before the Court of King's Bench or Common Pleas, and such court should thereupon determine whether the cause of his commitment were just, and should forthwith do as to justice should appertain. And by Statute 31 Charles II., c. 2, commonly called the "Habeas Corpus Act," amended and made more effectual by the 56 George I., c. 100, the methods of obtaining the writ of habeas corpus are so plainly pointed out and enforced that, so long as this statute remains unimpeached, no subject of England can be long detained in prison, except in those cases in which either the general law requires and justifies such detention, or else some special legislation (always regrettable) has been found necessary so to provide in exceptional circumstances. Moreover, lest the habeas corpus should be evaded by demanding unreasonable bail or sureties for the prisoner's appearance, it is declared, by a statute passed in the first year of the reign of William and Mary, that excessive bail ought not to be required, though, on the other hand, to prevent such abuses as are usually apt to occur in the resort to a writ of this description, it is a rule with the courts that they will not grant a habeas corpus as of course or without probable cause shown.
Of great importance to the public is the preservation of this personal liberty. If even the highest magistrate could imprison arbitrarily whenever he or his officers thought proper, as in pre-Revolutionary France was the frequent practice of the Crown, there would soon be an end of all other rights and immunities. Indeed, some have thought that unjust attacks even upon life or property at the arbitrary will of the ruler are less dangerous to the commonwealth than such as are made upon the personal liberty of the subject. To deprive a man of life, or by violence to confiscate his estate, without accusation or trial, would be so gross and notorious an act of despotism as must at once convey the alarm of tyranny throughout the whole kingdom; but confinement of the person by secretly hurrying him to gaol, where his sufferings are unknown or forgotten, is a less public, a less striking, and therefore a more dangerous engine of arbitrary government. And yet sometimes, when the State is in real danger, even this may be a necessary measure, as has frequently happened in the administration of Ireland. But the happiness of our constitution is that it is not left to the executive power to determine when the danger of the State is so great as to render this measure expedient, for Parliament alone, when it sees proper, by suspending the Habeas Corpus Act for a short and limited time, can enable the Crown to imprison suspected persons summarily, and without the possibility of their obtaining their discharge during that period by resort to the courts, as the Senate of Rome was wont to have recourse to a dictator when they judged the Republic to be in grave and imminent danger.
Habeas corpus as a form is not known to the law of Scotland. The way in which a person imprisoned gets his trial brought on, or his release if he is not brought to trial, is there called "Running Letters."