Certiorari is the writ by which, since the abolition of imprisonment for debt and the consequent disuse of the better known writ habeas corpus, causes are removed from inferior courts of record into the High Court of Justice. This is a matter of considerable importance to the commercial public. Such removal is either before or after judgment in the inferior court. Before judgment certiorari is competent as tort, in all cases except where the sum sued for is less than £5. Either party can remove the cause, but, where the sum is less than £20, the defendant must give his sureties for the debt and costs. The removal must be within six weeks after appearance of defendant. In the superior court the plaintiff must make a fresh statement of claim. The certiorari is obeyed by sending up the original record. Under the Judicature Acts there is a further power of removal when any defence or counter-claim is set up which is beyond the jurisdiction of the inferior court. In the county courts, where the action on contract is above £20, or on tort above £5, the defendant has a general right to certiorari on security for costs. Where the discretion of the superior court is appealed to, such considerations as the difficulty of legal points, the improbability of obtaining an impartial jury, are important. After judgment, certiorari is often applied for by the successful plaintiff for purposes of execution, where the person or effects of the defendant cannot be found in the jurisdiction of the inferior court. Certiorari may also be obtained as of right by the crown to remove an indictment in a criminal cause to the Queen's Bench Division or the Central Criminal Court. This writ used also to be of right to private prosecutors, but since the institution of the Court of Criminal Appeal it is necessary to show cause, as in a civil case from the county courts, and to give security.
In the United States, certiorari is generally provided for by statute, but where no such provision is made, or no other mode of review of the proceedings of an inferior court has been provided by statute, any superior court exercising common law jurisdiction has an inherent right to issue this writ. It is used in both civil and criminal cases to bring the whole record of the inferior tribunal before a superior court, to determine whether the former has proceeded within its jurisdiction, and also to enable substantial justice to be done whenever an inferior tribunal has failed to proceed according to the requirements of the law. It is used as an original process to remove a cause, and change venue, only where the superior court is satisfied that an impartial trial will not otherwise be had.