Officer Struble observed a car veer slowly onto the shoulder of the road for one or two seconds and then jerk back onto the road. Struble pulled the car over. His dog Officer Floyd, was in his patrol car that night. Two men were in the car: the driver, D, and a front-seat passenger, Scott Pollman. D claimed he had swerved to avoid a pothole. Struble gathered D’s license, registration, and proof of insurance, and asked D to accompany him to the patrol car. D asked if he was required to do so, and Struble answered that he was not. D decided to wait in his own vehicle. Struble returned and asked passenger Pollman for his driver’s license and began to question him about where the two men were coming from and where they were going. Pollman replied they went to look at a Ford Mustang that was for sale and that they were returning. Struble called for a second officer. Struble then began writing a warning ticket for D for driving on the shoulder of the road. Struble completed the stop and issued the warning and returned their documents. Struble asked for permission to walk his dog around D’s vehicle. D said no. Struble then instructed D to turn off the ignition, exit the vehicle, and stand in front of the patrol car to wait for the second officer. D complied. At 12:33 a.m., a deputy sheriff arrived. The dog alerted to the presence of drugs halfway through Struble’s second pass. Seven or eight minutes had elapsed from the time Struble issued the written warning until the dog indicated the presence of drugs. A search of the vehicle revealed a large bag of methamphetamine. D moved to suppress the evidence seized from his car on the ground that Struble had prolonged the traffic stop without reasonable suspicion in order to conduct the dog sniff. A Magistrate Judge recommended that the extension of the stop by “seven to eight minutes” for the dog sniff was only a de minimis intrusion on D’s Fourth Amendment rights and was therefore permissible. Everyone up the chain agreed, and the Supreme Court granted certiorari.