Delaware v. Prouse

While the State has an interest in ensuring the safety of its roadways, an individual still retains a reasonable expectation of privacy in a vehicle, despite significant governmental regulation of vehicles. If an individual was subjected to unrestricted governmental intrusion every time he or she entered a vehicle, the Fourth Amendment prohibition against unreasonable searches and seizures would be severely undermined. Instead, “except in those situations in which there is at least articulable and reasonable suspicion that a motorist is unlicensed or that an automobile is not registered, or that either the vehicle or an occupant is otherwise subject to seizure for violation of law, stopping an automobile and detaining the driver in order to check his driver’s license and the registration of the vehicle are unreasonable under the Fourth Amendment.”