The U.S. Supreme Court recently considered whether it was permissible under the Fourth Amendment for law enforcement officers to locate witnesses to a fatal hit-and-run accident by setting up a checkpoint to stop vehicles. This recent case, together with the rulings and language from four earlier decisions, may have wider application to the homeland security issues that agencies increasingly confront.
Near the Border
For many years, the court has upheld the constitutionality of briefly stopping vehicles at fixed checkpoints at or near international borders to check immigration status. In the 1976 opinion in U.S. v. Martinez-Fuerte, the court acknowledged that when Border Patrol officers cause a motorist to slow down or stop before passing through a checkpoint, a detention has occurred. "Checkpoint stops are 'seizures' within the meaning of the Fourth Amendment," said the court.
The general rule, of course, is that seizures must be supported by individualized suspicion that the person being seized is involved in criminal activity. When the Border Patrol stops vehicles at immigration checkpoints, there will not necessarily be any individualized suspicion that the occupants are in violation of immigration laws. The court therefore summarized the issue it considered in Martinez-Fuerte as, "whether a vehicle may be stopped at a fixed checkpoint for brief questioning of its occupants even though there is no reason to believe the particular vehicle contains illegal aliens."
Answering affirmatively, the court created an exception to the general rule by balancing the slight nature of the intrusion on the liberty of the motoring public with the significant need to address the serious problem of illegal immigration.
In Martinez-Fuerte, checkpoints had been used near the international border in Texas and California. They were fixed sites, with signs informing motorists of the nature of the checkpoints. Locations were chosen on major highways, and only a small percentage of vehicles were diverted for secondary inspection. On balance, the court reasoned that the public interest in interdicting illegal aliens outweighed the minimal intrusion, and held that "the stops and questioning at issue may be made in the absence of any individualized suspicion at reasonably located checkpoints."
In Michigan v. Sitz, the Supreme Court considered police use of a checkpoint to detect impaired drivers. The sites for the checkpoints were selected by supervisors, every approaching car was stopped by uniformed officers for a brief observation of signs of intoxication, and only where such indications were noted were the drivers diverted to secondary sites for a license check and further tests of impairment.
The Supreme Court again used a balancing test in upholding the lawfulness of the initial stops. The court found it important that individual officers did not make discretionary decisions about which cars to stop. Against the momentary inconvenience to stopped motorists, the court weighed the enormity of the risks of "death and mutilation" on the nation's highways posed by impaired drivers, and declared the sobriety checkpoints permissible under the Fourth Amendment.
On the other hand, the Supreme Court ruled that it was unconstitutional for police in Indianapolis to establish roadblocks for the purpose of allowing drug-sniffing dogs to circle each vehicle, looking for a hit. Whereas checkpoints might be justified to address illegal immigration and drunken driving, the court viewed the narcotics checkpoint as merely an intrusion on motorists' liberty in order to try to catch the occasional drug carrier. The Court reasoned that drug possession does not immediately threaten highway safety or the nation's territorial integrity.