The Supreme Court ruled unanimously that in evaluating whether a police officer had "reasonable suspicion" to detain a suspect briefly for questioning, courts should pay more attention to the officer's experience and the event's overall context than to individual parts of an incident.

The case concerned a federal border patrol agent's stop of a minivan carrying two adults and three children on an unpaved road in a remote area of southern Arizona. The vehicle was found to be carrying 128 pounds of marijuana, but the federal appeals court in San Francisco ruled that the stop was unconstitutional because the border patrol agent did not have reasonable suspicion.

The appeals court looked at the incident in separate components, such as the minivan driver slowing abruptly when he saw the patrol car, avoiding eye contact with the agent, and the children in the back seat waving at teh agent in an oddly mechanical manner, as if they had been instructed to do so. The appeals court ruled that these events were "insufficient to give rise to reasonable suspicion."

In his opinion, Chief William H. Rehnquist said the appeals court's assessment of the case's individual factors was inconsistent with the Supreme Court's insistence in its precedents that reasonable suspicion be based on a "totality of the circumstances."

Rehnquist said the border patrol agent, Clinton Stoddard, "was entitled to make an assessment of the situation in light of his specialized training and familiarity with the customs of the area's inhabitants."