A writ of certiorari is a writ, or order, sent from a higher court to a lower one which orders the lower court to turn over transcripts and documents related to a specific case for review. In general, a writ of certiorari is issued by the highest court in a nation after a request from a petitioner. The decision to grant such a writ is made at judicial discretion.

The term comes from a Latin word which means “to be ascertained” or “to make certain.” A writ of certiorari is one of the ways in which a high court can review a case. When a petitioner asks for a writ of certiorari, the request must include an explanation of why the petitioner is resorting to a writ. The request must also indicate what in the case is under dispute, so that justices are aware of what they are being asked to review.

When a request for a writ of certiorari is submitted to a high court, clerks review it before passing it on to the justices. The justices vote on which cases shall be granted writs. In the United States, less than 5% of the requests for a writ of certiorari are granted, due to the high volume of requests and the busy court schedule. In Supreme Court shorthand, this is a “Cert. Denied.” When a writ is denied, it does not necessarily mean that the higher court approves of the actions of the lower court, and the denial cannot be viewed as the court's final statement on the issue.

Since most high courts are responsible for interpreting and defending national constitutions and the law, justices tend to grant writs for controversial cases, or cases which may set a precedent. Once a lower court has been served with a writ of certiorari, it must turn the requested material over to the higher court. After review, the justices offer a decision on the material, either affirming the decision of the lower court, or rejecting it. In most cases, and majority and minority both submit a written opinion of the case.

Petitioners should consider a writ of certiorari a technique of last resort. Since the writ must include a reason why the petitioner has no other avenue of redress, it is important to explore all of the ways in which a legal problem can be addressed before submitting it to the highest court. In most nations, the judicial system has a tiered appeals process which should be followed first, in addition to other legal means which a lawyer may suggest.