What legal document compels a witness to appear and testify in court?

A subpoena is the legal document that compels a witness to appear and testify in court. This instrument is an essential tool in the legal process, ensuring that individuals with relevant information can be brought before the court to provide their testimony, which can be critical for establishing facts in a case. A subpoena can also require the production of documents, records, or evidence pertinent to the matter at hand.

The other options do not perform the same function. An affidavit is a written statement made under oath, used primarily to present evidence in a written format rather than summons an individual to testify in person. A writ of certiorari is a type of order by which a higher court reviews a case from a lower court; it does not compel witness testimony. A summons is typically a document issued to notify a defendant that a legal action has been initiated against them and to request their appearance in court, but it does not specifically address compelling witnesses to testify.