Gerstein v. Pugh

Probable cause is the constitutional standard governing arrest. It balances the individual's interest in liberty against the government's interest in enforcing criminal law, permitting arrest when facts and circumstances would lead a prudent person to believe that the suspect committed or was committing an offense.

Police may make a warrantless arrest on their own on-the-scene assessment of probable cause because requiring advance judicial approval in every case would unduly burden legitimate law enforcement. But once the suspect is in custody, the practical reasons for dispensing with a magistrate's judgment largely disappear: the suspect cannot flee while police present their evidence, and the need for neutral review becomes more pressing.

Extended pretrial detention imposes serious harms distinct from the initial arrest. It can cost a person a job and income, disrupt family life, and burden even a released defendant through restrictive conditions of release. The Fourth Amendment therefore requires the detached judgment of a neutral judicial officer before the State may continue a significant restraint on liberty.

The rule also accords with common-law practice. An arrested person was ordinarily brought promptly before a justice of the peace, who examined the prisoner and available evidence, then discharged, bailed, or committed the person. That historical practice informed the Fourth Amendment's conception of a reasonable seizure.

A prosecutor who conscientiously decides that the evidence supports a charge may provide some protection against unfounded detention. But the prosecutor is part of the law-enforcement process and cannot serve as the neutral and detached magistrate the Fourth Amendment requires for an extended deprivation of liberty.

The Court's prior decisions establish that probable cause for an arrest warrant must be determined by someone independent of police and prosecution. The separation is designed to guard against even well-intentioned overzealousness in criminal enforcement by dividing authority among different officials.

The Court distinguished the validity of detention from the validity of prosecution itself. A judicial probable-cause hearing is not a constitutional prerequisite to prosecution by information, and an unlawful arrest or pretrial detention does not invalidate a later conviction. The constitutional requirement concerns the present justification for significant pretrial custody or restraint, not judicial supervision of prosecutorial charging discretion.

The only question at this stage is whether there is probable cause to detain the arrested person pending further proceedings. That is the same practical, probability-based standard that governs arrest, not a determination of guilt or even a full assessment of whether the State can prove its case at trial.

Traditionally, magistrates have determined probable cause in nonadversary proceedings that may rely on written materials and hearsay. Because probable cause does not ordinarily require the fine resolution of factual conflicts or credibility disputes demanded by proof beyond a reasonable doubt, an informal procedure can reliably decide the limited question.

The required determination is not a critical stage requiring appointed counsel. Unlike the adversary preliminary hearing at issue in Coleman v. Alabama, this proceeding does not decide whether the State may prosecute and does not require the prosecution to present witnesses whose testimony must be explored or preserved for trial.

States retain flexibility to integrate the determination into a first appearance, bail proceeding, or another component of their pretrial system. Whatever procedure a State selects, it must furnish a fair and reliable judicial probable-cause determination promptly after a warrantless arrest when the defendant faces significant pretrial restraint.