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 Maryland, as in other states, an arrest warrant is a legal document issued by a judge or magistrate that authorizes law enforcement to take an individual into custody on suspicion of a crime. The issuance of an arrest warrant in Maryland must be based on probable cause, which aligns with the Fourth Amendment of the U.S. Constitution. This means there must be sufficient evidence or reasonable grounds to believe that the person named in the warrant has committed a criminal offense. The process of obtaining an arrest warrant typically involves law enforcement presenting evidence to a judge or magistrate, who then determines whether the standard of probable cause is met. Maryland law also recognizes exceptions to the warrant requirement, such as when a crime is witnessed by a police officer, which allows for an arrest to be made without a warrant. The purpose of an arrest warrant is to safeguard individuals from arbitrary arrests by ensuring that a neutral and detached authority reviews the circumstances before an arrest is made, and to inform the accused of the specific charges they are facing.