The United States Supreme Court held that an officer can inquire into matters unrelated to the justification for her traffic stop so long as the inquiry does not measurably extend the stop.

Police officers were patrolling a neighborhood in Tucson, AZ that was associated with the Crips gang. They stopped a vehicle to issue a citation for a violation. The back-seat passenger, Johnson (defendant), was asked to get out of the car after the Officer learned that he was from a town with a Crips gang and that he had previously been in prison. After exiting the car, the two of them had a conversation about his gang affiliation. Because the Officer expected that Johnson was armed, she patted him down and felt the butt of a gun. He struggled but was handcuffed.

Johnson was charged with possession of a weapon by a prohibited possessor. The trial court denied his motion to suppress the evidence, concluding that the stop was lawful and that the Officer had cause to suspect that Johnson was armed and dangerous.

The Arizona Court of Appeals reversed and the Supreme Court of Arizona denied review. The United States Supreme Court granted certiorari. The Supreme Court began with a review of Terry v. Ohio, stating the when a stop is justified by suspicion that criminal activity is afoot, the police officer must be positioned to act instantly on reasonable suspicion that the persons temporarily detained are armed and dangerous. A limited search of outer clothing for weapons serves to protect both the officer and the public and thus, a patdown is constitutional.

The Arizona Court of Appeals recognized that, initially Johnson was lawfully detained incident to the legitimate stop of the vehicle in which he was a passenger. However, the Court of Appeals also determined that when the Officer began questioning Johnson about matters unrelated to the traffic stop, the patdown authority ceased to exist, absent reasonable suspicion that Johnson had engaged in, or was about to engage, in criminal activity.

The U.S. Supreme Court disagreed with the findings of the Arizona Court of Appeals. The Court stated in Muehler v. Mena, 544 U.S. 93 (2005) that "an officer's inquiries into matters unrelated to the justification for the traffic stop, this Court has made plain, do not convert the encounter into something other than a lawful seizure, so long as those inquires do not measurably extend the duration of the stop."

In sum, "a traffic stop of a car communicates to a reasonable passenger that he or she is not free to terminate the encounter with the police and move about at will." There was nothing in the interaction that would have led Johnson to believe that the stop had ended or that he was otherwise free to leave without the Officer's permission. The Officer was not constitutionally required to give Johnson an opportunity to leave without first ensuring that, in doing so, she was not permitting a dangerous person to leave the scene.

The court observed: "'The risk of harm to both the police and the occupants [of a stopped vehicle] is minimized,'" we have stressed, "'if the officers routinely exercise unquestioned command of the situation.'" Maryland v. Wilson, 519 U.S. 408, (1997) (quoting Michigan v. Summers, 452 U.S. 692, (1981). Three decisions cumulatively portray Terry's application in a traffic-stop setting: Pennsylvania v. Mimms, 434 U.S. 106 (1977) (per curiam); Maryland v. Wilson, 519 U.S. 408 (1997); and Brendlin v. California, 551 U.S. 249 (2007).

In Mimms, the Court held that once a motor vehicle has been lawfully detained for a traffic violation, the police officers may order the driver to get out of the vehicle without violating the Fourth Amendment's proscription of unreasonable searches and seizures." The government's "legitimate and weighty" interest in officer safety, the Court said, outweighs the "de minimis" additional intrusion of requiring a driver, already lawfully stopped, to exit the vehicle. Citing Terry as controlling, the Court further held that a driver, once outside the stopped vehicle, may be patted down for weapons if the officer reasonably concludes that the driver "might be armed and presently dangerous."

Wilson held that the Mimms rule applied to passengers as well as to drivers. Specifically, the Court instructed that "an officer making a traffic stop may order passengers to get out of the car pending completion of the stop." "The same weighty interest in officer safety," the Court observed, "is present regardless of whether the occupant of the stopped car is a driver or passenger."

It is true, the Court acknowledged, that in a lawful traffic stop, "there is probable cause to believe that the driver has committed a minor vehicular offense," but "there is no such reason to stop or detain the passengers." On the other hand, the Court emphasized, the risk of a violent encounter in a traffic-stop setting "stems not from the ordinary reaction of a motorist stopped for a speeding violation, but from the fact that evidence of a more serious crime might be uncovered during the stop." "The motivation of a passenger to employ violence to prevent apprehension of such a crime," the Court stated, "is every bit as great as that of the driver." Moreover, the Court noted, "as a practical matter, the passengers are already stopped by virtue of the stop of the vehicle," so "the additional intrusion on the passenger is minimal," Completing the trilogy, Brendlin held that a passenger is seized, just as the driver is, "from the moment [a car stopped by the police comes] to a halt on the side of the road." A passenger therefore has standing to challenge a stop's constitutionality. After Wilson, but before Brendlin, the Court had stated, in dictum, that officers who conduct "routine traffic stop[s]" may "perform a 'patdown' of a driver and any passengers upon reasonable suspicion that they may be armed and dangerous." Knowles v. Iowa, 525 U.S. 113, (1998). That forecast was confirmed by the Supreme Court to accurately capture the combined thrust of the Court's decisions in Mimms, Wilson, and Brendlin.

So in the situation at hand, a limited search of outer clothing for weapons served to protect both the officer and the public and thus, the patdown was constitutional.

The judgment of the Arizona Court of Appeals was reversed and the case remanded for further proceedings.