A person called 9-1-1 reporting that a truck driver was driving dangerously and had just run the person off the road. The person gave the make, model, color, and license plate number of the truck to the State of California (plaintiff) highway patrol. A police officer saw the truck, driven by Lorenzo Navarette (defendant), on the highway and followed it for five minutes before pulling it over. The officer did not note any reckless driving in the time he was following the truck. Upon approaching the truck, the officer smelled marijuana. The officer searched the truck and found 30 pounds of marijuana. Navarette challenged the constitutionality of the traffic stop and incident search. The trial court found the stop and search to be constitutional. The California Court of Appeal affirmed. The California Supreme Court denied review. The United States Supreme Court granted certiorari.