A subpoena is a writ by a court, that has authority to compel testimony by a witness or production of evidence under a penalty for failure. There are two common types of subpoena:
1.subpoena ad testificandum
- orders a person to testify before the ordering authority or face punishment. The subpoena can also request the testimony to be given by phone or in person.
2.subpoena duces tecum
- orders a person or organization to bring physical evidence before the ordering authority or face punishment. This is often used for requests to mail copies of documents to requesting party or directly to court.
Legally, a summons (also known in England and Wales as a claim form) is a legal document issued by a court (a judicial summons) or by an administrative agency of government (an administrative summons) for various purposes.
The summons announces a date by which the defendant(s) must either appear in court, or respond in writing to the court or the opposing party or parties. The summons is the descendant of the writ of the common law. It replaces the former procedure at common law by which the plaintiff actually had to ask the sheriff to arrest the defendant in order for the court to obtain personal jurisdiction in both criminal and civil actions.
In most U.S. jurisdictions, the service of a summons is in most cases required for the court to have personal jurisdiction over the party who is being "hauled" into court involuntarily. The process by which a summons is served is called service of process. The form and content of service in the federal courts is governed by Rule 4 of the Federal Rules of Civil Procedure, and the rules of many state courts are similar. The federal summons is usually issued by the clerk of the court. In many states the summons may be issued by an attorney, but some states use filing as the means to commence an action and in those states the attorney must first file the summons in duplicate before it becomes effective; one or more copies are stamped by the court clerk with the court seal and returned to the attorney, who then uses it to actually serve the defendants. Other jurisdictions may only require that the summons be filed after it is served on the defendants. New York is notorious for its permissive filing system, in which the summons or complaint need not be filed at all.