A search warrant is a legal document issued by a judge or magistrate that authorizes law enforcement officers to conduct a search of a person, location, or vehicle and seize specific items. Under the Fourth Amendment to the U.S. Constitution, warrants require "probable cause" — a reasonable basis to believe that a crime has been committed and that evidence of that crime is at the location to be searched. Warrant applications must specify the place to be searched and the items to be seized. In federal cases, the FBI must apply for a search warrant through a federal magistrate judge, who reviews the warrant affidavit for probable cause before issuing or denying it. Courts can later suppress evidence obtained through improperly issued warrants.