A border-patrol agent working in an area of Arizona often travelled by smugglers received an alert that a traffic sensor had been triggered. The agent went to investigate. Based upon his experience, the agent became suspicious that Ralph Arvizu (defendant) might be smuggling contraband. The agent based this suspicion on numerous facts including the van occupants’ behavior, Arvizu’s effort to avoid checkpoints, the peculiar elevation of the back passenger’s knees, the fact that the van’s registered address was in an area populated by smugglers, and the fact that minivans are commonly used for smuggling. The agent pulled Arvizu over, and Arvizu consented to a search of the vehicle. The agent found over 100 pounds of marijuana in the van. Arvizu was arrested for possession with the intent to distribute marijuana. Arvizu moved to suppress the evidence obtained during the stop on the basis that the stop was unreasonable under the Fourth Amendment. The United States District Court for the District of Arizona denied the motion. The United States Court of Appeals for the Ninth Circuit reversed, finding that none of the relevant facts gave rise to reasonable suspicion.