The Supreme Court in this case made it clear that police officers may not ordinarily stop a person’s car without probable cause or reasonable suspicion of criminal activity. The car in Delaware v. Prouse was stopped by a police officer who had not observed any suspicious activity at all. He claimed to have made the stop randomly, just to make a spot check to see if the driver possessed his license and registration.
Upon approaching the stopped car, the officer smelled marijuana and, ultimately, he found some inside. The Court held that the marijuana should be suppressed because the officer had no right under the Fourth Amendment to the Constitution to stop the car, given the driver’s reasonable expectation of privacy.
Justice White reasoned for the majority that permitting such suspicionless spot checks would only contribute marginally, if at all, to the goal of highway safety. Since the Court could not ‘‘conceive of any legitimate basis upon which a patrolman could decide that stopping a particular driver for a spot check would be more productive than stopping any other driver,’’ approving such stops would have created a ‘‘grave danger’’ of abuse of discretion. ‘‘This kind of standardless and unconstrained discretion,’’ Justice White concluded, ‘‘is the evil the Court has discerned when . . . it has insisted that the discretion of the official in the field be circumscribed.’’
Subsequent Supreme Court decisions have permitted police to operate suspicionless, drunk-driving roadblocks when they take great care to avoid this sort of ‘‘standardless and unconstrained discretion’’ in the selection of cars to be stopped. But, the core of the Prouse decision remains vital and has been applied in other settings as well—for example, when a city sought to stop cars simply to see whether occupants possessed drugs.
JOHN M. BURKOFF