Introduction

Probable Cause and Arrest Procedure

Introduction

The Fourth Amendment protects "[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures."¹ A person is seized when officers take control of that person's liberty, and an arrest is the fullest version of that control: the officers take the person into custody and end the freedom to walk away. Because an arrest is a seizure of a person, it must be reasonable under the circumstances, and each question in this chapter is a different way of asking whether a particular arrest met that standard.² In District of Columbia v. Wesby, the Court gave the baseline: a warrantless arrest is reasonable if the officer has probable cause to believe the suspect committed a crime in the officer's presence.³ Probable cause is the officer's reasonable basis for that belief. It requires only a probability or substantial chance of criminal activity, not proof that a crime occurred.⁴

The place of the arrest decides whether anything more than probable cause is needed. Many searches are presumed unreasonable when conducted without a warrant, but an arrest in a public place carries no such presumption, so officers may make a full custodial arrest on probable cause without first asking a magistrate for permission.⁵ An arrest inside a home is different, because the home carries the strongest expectation of privacy, and the Fourth Amendment therefore requires an arrest warrant or a search warrant there.⁶ Those two rules mean that most arrest problems reduce to three questions, asked in order. The first is whether the police made a custodial arrest at all, and if so, whether they had probable cause for it. The second is whether a warrant was required, which turns mainly on whether the officers entered a home to make the arrest. The third is whether the federal rules on issuing, executing, and serving warrants and summonses, and on bringing the arrestee before a judge, were followed.

Those questions sit in two layers of law. The constitutional layer, covering probable cause, warrants, and the special protection of the home, sets the floor that every arrest in the country must clear. The statutory layer, found in the Federal Rules of Criminal Procedure, governs the mechanics of federal arrests: what a warrant must say, who may carry it out and where, when a summons replaces a warrant, and what must happen once the defendant is in custody. A complete answer to an arrest problem therefore has to run both layers, because an arrest that satisfies the Fourth Amendment can still be followed by a procedural misstep, and a carefully followed procedure cannot rescue an arrest that lacked probable cause. All of this machinery applies only when police conduct amounts to an arrest, so the first section asks when a detention crosses that line.