United States v. Cortez, 449 U.S. 411 (1981), was a United States Supreme Court decision clarifying the reasonable suspicion standard for the investigative stop of a vehicle. Background Border Patrol officers were monitoring a remote section of the southern Arizona desert known to be a common point for illegal border crossings. The officers repeatedly found human footprints in the sand that indicated that groups of 8 to 20 persons had walked north from the Mexican border to Arizona State Route 86. This pattern of footprints appeared numerous times, always on weekend nights under clear skies. There was also a shoe print with a chevron shape that consistently reappeared, leading the officers to nickname the suspected guide "Chevron." In late January 1977, Border Patrol officers noticed it had been two weeks since the footprints were last seen, and, moreover, it had rained on Friday and Saturday, meaning that Sunday, January 30/31 would be a likely night for "Chevron" to lead another crossing. The Border Patrol officers waited a few miles from where the footprints usually met the state highway. The officers waited from 2 am to 6 am. In this desolate area, only around 15 vehicles passed by, and only two were large enough to fit a large number of passengers. Of these vehicles, a pickup truck with a camper shell passed the officers at 4:30 am going westbound. Then, at 6:12 am, the same vehicle passed the officers again going eastbound. The officers then stopped the vehicle. They found six unauthorized immigrants in the back of the camper, and arrested Jesus Cortez, the vehicle's driver. The Ninth Circuit ruled that the officers did not have a sufficient basis to justify the stop. The Court of Appeals relied on United States v. Brignoni-Ponce, ruling that the officers "did not have a valid basis for singling out the Cortez vehicle" and had violated Cortez's Fourth Amendment rights. Opinion of the Court The Supreme Court unanimously reversed the Ninth Circuit, ruling that the Border Patrol had reasonable suspicion to stop Cortez's vehicle. Chief Justice Burger emphasized that reasonable suspicion must be based on the "totality of the circumstances," and does not depend on "hard certainties, but ... probabilities." Officers who stop a vehicle must have a "particularized and objective basis for suspecting the particular person stopped," but are allowed to use their experience and training to "draw inferences and make deductions." The Court