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."
Sobriety