An arrest warrant is a written order from a judge or magistrate that commands the police or other authority to physically take a person accused of a criminal offense into custody. The Fourth Amendment to the United States Constitution requires an arrest warrant to be supported by probable cause—which means there is a reasonable basis to believe the person to be arrested committed a crime.

Arrest warrants protect people from unlawful arrests by requiring the independent review of supporting facts by a person (judge or magistrate) who is not involved in the process of investigating the alleged crime. Arrest warrants also give the accused actual notice of the charge of a criminal offense committed by the accused. Arrest warrants are generally required to take an accused into physical custody unless there is an exception to the warrant requirement—such as when the crime is committed in the presence of the arresting officer.

In Massachusetts, an arrest warrant is a legal document issued by a judge or magistrate that authorizes law enforcement to take a person into custody on suspicion of having committed a criminal offense. Consistent with the Fourth Amendment of the U.S. Constitution, Massachusetts law requires that an arrest warrant be based on probable cause, which is established when there is a reasonable basis to believe that the individual has committed a crime. The process of obtaining an arrest warrant involves presenting evidence to a neutral judge or magistrate, who must then determine whether the evidence is sufficient to justify the arrest. This process ensures that individuals are protected from arbitrary arrests. While arrest warrants are typically necessary to arrest someone who is not in the immediate presence of law enforcement, there are exceptions to this requirement. For example, if a crime is committed in an officer's presence, or in certain exigent circumstances, an officer may make an arrest without a warrant.