United States v. Cortez

Border Patrol officers patrolling a sparsely populated area of southern Arizona repeatedly discovered distinctive human footprints in the desert over roughly two months, indicating that groups of 8 to 20 people were being guided north from the Mexican border across 30 miles of desert to a pickup point on Highway 86. One recurring footprint had a distinctive chevron-shaped pattern, and officers nicknamed its wearer Chevron. From the pattern and timing of the tracks, officers deduced that Chevron typically operated on clear nights near weekends, that a vehicle picked up the group and approached from and returned to the east, and that the pickup generally occurred between 2 and 6 a.m. On a night officers believed a crossing was likely, given a two-week gap since the last tracks and recent rain, they staked out a position along the highway and observed a pickup truck with a camper shell pass going west and then, about the time needed for a round trip to the suspected pickup point, pass again going east. Officers stopped the truck; the driver, Cortez, and passenger Hernandez-Loera, who wore shoes matching the chevron pattern, were inside, along with several undocumented aliens in the camper. Cortez and Hernandez-Loera were convicted of transporting illegal aliens after the district court denied their motion to suppress the evidence from the stop; the Ninth Circuit reversed, holding the officers lacked a sufficient basis to justify the stop.