An arrest is using legal authority to deprive a person of his or her freedom of movement. An arrest is generally made with an arrest warrant. An arrest may be made without a warrant if probable cause and exigent circumstances are presented at the time of the arrest.
Probable cause is a reasonable belief of the police officer in the guilt of the suspect, based on the facts and information prior to the arrest. For instance, a warrantless arrest may be legitimate in situations where the police officer has a reasonable belief that the suspect has either committed a crime or is about to commit a crime. The police officer might also arrest the suspect to prevent the suspect’s escape or to preserve the evidence. A warrantless arrest may be invalidated though, if the police officer failed to demonstrate exigent circumstances and probable cause.
The right to make warrantless arrests are commonly defined and limited by statutes subject to the due process guaranty of U.S. Constitution. The suspect arrested without a warrant is entitled prompt judicial determination generally made in 48 hours.