In order to interdict illegal drugs, the city of Indianapolis began to set up vehicle checkpoints in 1998. The city had six such checkpoints, and between August and November of 1998 it stopped 1,161 vehicles and arrested 104 motorists. Fifty five of the arrests were for drug related offenses, while forty nine were unrelated to drugs. The procedure is as follows: At each checkpoint the police stop a predetermined number of vehicles, and the driver is asked for a license and the car registration. The driver in each case is inspected for signs of impairment. The directives authorize that the police can conduct a search only by consent or if they have “particularized suspicion.” The officers must stop each car in a particular sequence, and they cannot stop vehicles out of sequence. A dog was used to sniff around the car. Moreover, officers have no discretion to vary the predetermined plan for the checkpoint search. Edmond (plaintiff) and Palmer (plaintiff) were stopped at such a checkpoint in September 1998. They filed a class action lawsuit on behalf of all motorists who were, or would be, stopped. Edmond and Palmer claimed the roadblocks violated the Fourth Amendment. The court of appeals held that the roadblocks did violate the amendment. The United States Supreme Court granted certiorari.