Prior to trial on federal drug charges, they moved for suppression of the evidence, arguing that the stop had not been justified by either a reasonable suspicion or probable cause to believe petitioners were engaged in illegal drug dealing activity, and that the officers' traffic violation ground for approaching the truck was pretextual. The motion to suppress was denied, petitioners were convicted, and the Court of Appeals affirmed. The temporary detention of a motorist upon probable cause to believe that he has violated the traffic laws does not violate the Fourth Amendment 's prohibition against unreasonable seizures, even if a reasonable officer would not have stopped the motorist absent some additional law enforcement objective. Petitioners claim that, because the police may be tempted to use commonly occurring traffic violations as means of investigating violations of other laws, the Fourth Amendment test for traffic stops should be whether a reasonable officer would have stopped the car for the purpose of enforcing the traffic violation at issue. However, this Court's cases foreclose the argument that ulterior motives can invalidate police conduct justified on the basis of probable cause.
Subjective intentions play no role in ordinary, probable cause Fourth Amendment analysis.
See, e.g., Robinson, supra, at 236. Nor can the Fourth Amendment 's protections be thought to vary from place to place and from time to time, which would be the consequence of assessing the reasonableness of police conduct in light of local law enforcement practices. Where probable cause exists, this Court has found it necessary to engage in balancing only in cases involving searches or seizures conducted in a manner unusually harmful to the individual. The making of a traffic stop out of uniform does not remotely qualify as such an extreme practice. Scalia, J., delivered the opinion for a unanimous Court.