## Facts

- A Delaware patrolman stopped a vehicle to check the driver’s license and the car’s registration.
- Before the stop, the officer observed no traffic or equipment violations and no suspicious activity.
- The stop was not conducted under any departmental or statewide standards, guidelines, or procedures for document checks.
- After the stop, the officer saw marijuana in plain view on the car floor and seized it.
- William J. Prouse, III was indicted for illegal possession of a controlled substance.
- The trial court suppressed the evidence, finding the stop “wholly capricious” and in violation of the Fourth Amendment.
- The Delaware Supreme Court affirmed; the U.S. Supreme Court granted certiorari and held it had jurisdiction because the state court’s judgment depended on federal constitutional law.

## Issues

1. Whether stopping a vehicle to check a driver’s license and registration, without any articulable and reasonable suspicion and without neutral standards limiting officer discretion, is an unreasonable seizure under the Fourth and Fourteenth Amendments.
2. Whether the Supreme Court had jurisdiction where the state court referenced the state constitution but its judgment depended on federal constitutional grounds.

## Decision

- The Court held it had jurisdiction because the state court did not clearly rest its judgment on an independent and adequate state ground.
- The Court affirmed the suppression ruling, holding that stopping an automobile and detaining its occupants to check license and registration, absent at least articulable and reasonable suspicion, is unreasonable under the Fourth Amendment.
- The Court emphasized that a traffic stop, even if brief and for a limited purpose, is a “seizure” within the meaning of the Fourth and Fourteenth Amendments.
- The Court concluded that Delaware’s interests in roadway safety and licensing enforcement did not justify suspicionless, discretionary spot checks conducted at an officer’s unstructured discretion.
- The Court noted that less discretionary, systematic approaches (e.g., stops conducted under neutral criteria) were not foreclosed by its holding.
- Vote: 8–1 (White, J.); Blackmun, J., concurring (joined by Powell, J.); Rehnquist, J., dissenting.

## Legal Principles

- Stopping an automobile and detaining its occupants, even briefly and for limited purposes, constitutes a Fourth Amendment seizure.
- Reasonableness is assessed by balancing the intrusion on Fourth Amendment interests against the promotion of legitimate governmental interests.
- Absent at least articulable and reasonable suspicion that a motorist is unlicensed, a vehicle is unregistered, or the vehicle/occupants are otherwise subject to seizure for a legal violation, a license-and-registration stop is unreasonable.
- Unstructured officer discretion in choosing which motorists to stop heightens the risk of arbitrary enforcement and weighs against Fourth Amendment reasonableness.
- The Fourth Amendment permits roadway enforcement methods that meaningfully constrain discretion through neutral standards and procedures, even where individualized suspicion is not present.

## Conclusion

The Court held that random, discretionary stops to check a driver’s license and vehicle registration—unsupported by articulable and reasonable suspicion and unconstrained by neutral standards—are unreasonable seizures under the Fourth Amendment, and evidence discovered as a result of such a stop must be suppressed.


Delaware v. Prouse, 440 U.S. 648 (1979)