The writ of _habeas corpus_ provides a remedy for jurisdictional and constitutional errors at the trial without limit as to time.[1440] It may be used to correct errors of that order made by military as well as by civil courts.[1441] Under the common law and the Act 31 Car. II c. 2 (1679), where a person was detained pursuant to a conviction by a court having jurisdiction of the subject matter, _habeas corpus_ was available only if a want of jurisdiction appeared on the face of the record of the Court which convicted him. A showing in a return to a writ that the prisoner was held under final process based upon a judgment of a court of competent jurisdiction closed the inquiry.[1442] Under the Judiciary Act of 1789[1443] the same rule obtained.[1444] But by the act of February 5, 1867,[1445] Congress extended the writ to all persons restrained of their liberty in violation of the Constitution or a law or treaty of the United States, and required the Court to ascertain the facts and to "dispose of the party as law and justice require." This gave the prisoner a right to have a judicial inquiry in a court of the United States into the very truth and substance of the causes of his detention. The Supreme Court has said that there is "no doubt of the authority of the Congress to thus liberalize the common law procedure on _habeas corpus_ * * *" .[1446] Habeas Corpus Not a Substitute for Appeal Since the writ of _habeas corpus_ is appellate in nature, Congress may confer jurisdiction to issue it upon the Supreme Court as well as upon the inferior federal courts.[1447] The proceeding may not, however, be used as a substitute for an appeal or writ of error.[1448] But if special circumstances make it advantageous to use this writ in aid of a just disposition of a cause pending on appeal it may be used for that purpose.[1449] Where facts dehors the record, which are not open to consideration upon appeal, are alleged to show a denial of constitutional rights, a judicial hearing must be granted to ascertain the truth or falsity of the allegations.[1450] Issuance of the Writ