Although traffic stops are not the most burdensome seizures regulated by the FOURTH AMENDMENT, they have become among the most controversial?partly because they are so common. Most Americans have never been arrested, but the vast majority have been pulled over. More importantly, traffic enforcement is highly discretionary. Vehicle codes are so widely breached that the police can stop almost any car if they follow it with a modicum of patience. This discretion is a boon for law enforcement; police departments increasingly have found vehicle codes a useful tool for finding and apprehending violators of more serious laws.
But the discretionary nature of traffic enforcement also has a worrisome side. Because vehicle codes give police officers authority to stop practically any motorist, they present some of the same risks of arbitrariness posed in colonial America by GENERAL WARRANTS and WRITS OF ASSISTANCE, the very instruments against which the Fourth Amendment was most clearly aimed. And a growing body of evidence suggests that the police are far more likely to pull over cars driven by members of racial minorities, particularly African Americans, and that minority motorists stopped by the police are more likely to be verbally or physically abused.
Recent decisions by the Supreme Court have exacerbated these dangers. In the most important of these decisions, Whren v. United States (1996), the Court held unanimously that the police can stop a car whenever they have PROBABLE CAUSE to believe that the driver has violated traffic laws, regardless of the officers' true motivation, and regardless of whether the violation would prompt a reasonable officer to pull the car over. Whren put to rest a persistent ambiguity in constitutional CRIMINAL PROCEDURE, ruling that "[s]ubjective intentions play no role in ordinary, probable-cause Fourth Amendment analysis." The decision also rejected the reasoning of some scholars and lower courts that a traffic stop should be deemed unconstitutionally pretextual if it departed so sharply from usual police practices that a reasonable officer would not have made the stop for the reasons given. Writing for the Court, Justice ANTONIN SCALIA saw this alternative approach as an unwieldy and unjustifiable attempt to bring subjective intentions back into the analysis through the back door.
In other recent cases the Court has broadened the power that the police can exercise once they pull over...