Subpoenas and warrants are both legal documents issued by a court, but that's where the similarity ends. The focus, purpose and intended recipient of each document distinguishe one from the other.
A subpoena is a court order that requires an eyewitness or a material witness to appear in a specific place, such as an attorney’s office or in court, on a specific date and time to provide sworn testimony about what the person saw, heard or knows -- or to provide relevant documents.
Unlike with a warrant, a subpoena applies in both civil and criminal cases. In a civil case, the focus is usually an out-of-court deposition conducted to gather information during the discovery phase. In a criminal case, a subpoena can be issued to someone to provide pre-trial information or to appear as a witness during a trial.
Unlike a warrant, a subpoena that pertains to a civil matter can be issued by an attorney; the issuer doesn't have to be a judge. According to FindLaw, the only time a judge or court commissioner must issue the order in a civil proceeding is when the recipient is a high-level government official. Subpoena delivery takes place well in advance of the required appearance date. A subpoena must be hand delivered by a sheriff, a process server or anyone who is 18 or older and not a party to the case.
A warrant is a court order that authorizes law enforcement personnel to search or seize property or arrest a person suspected of committing a crime. The U.S. Constitution requires a warrant to protect an accused person’s Fourth Amendment rights.
Unlike with a subpoena, a judge must always issue a warrant -- and only if the request meets the “probable cause” standard. Probable cause requires some type of evidence, not just a suspicion of a crime. Although a warrant is hand-delivered just as a subpoena is, law enforcement personnel deliver a search-or-seizure warrant while executing it and an arrest warrant before or after the arrest.