Because the government has a unique interest in policing its borders at and around border crossings, and because people have a lower reasonable expectation of privacy at such places, police officers can search cars and their occupants even if they have no reason to be suspicious. Essentially, neither citizens nor noncitizens have Fourth Amendment rights in these situations, with few exceptions (personal searches, such as strip-searches and body-cavity searches, may require a warrant).

Broad Definition of "Border"

Customs or immigration officials may conduct warrantless searches without probable cause not only at borders, but at their "functional equivalents," such as international airports. Essentially, neither citizens nor noncitizens have Fourth Amendment rights in these situations.

Permanent Checkpoints

Border officials may stop motorists at fixed checkpoints that are reasonably located relative to the border, to question motorists even in the absence of reasonable suspicion of a crime, let alone probable cause. (U.S. v. Martinez-Fuerte, U.S. Supreme Court, 1976.) The right to search in the absence of suspicion allows police to dismantle a car, and even extends to searching a vehicle’s gas tank (U.S. v. Flores-Montano, U.S. Sup. Ct. 2004).

Roving Patrols

Police using roving patrols need a reasonable suspicion that crime is afoot before they can stop a car, unlike the broader right to stop and search at the border. However, the fact that occupants appear to be Hispanic will not, by itself, justify a roving patrol stop. (U.S. v. Brignoni-Ponce, U.S. Supreme Court, 2004.) Patrols may not search a car without a warrant unless an exception to the warrant requirement applies, such as when occupants give consent.

Getting Professional Help

Whether the stop and search in your case was valid will depend on how appellate courts in your state have decided in cases involving facts such as yours. You'll need the help of an experienced criminal defense attorney to know where you case falls within the "valid-not valid" spectrum of cases.