The following is a general discussion of federal case law on probable cause and traffic stops.
A traffic stop is a “seizure” within the meaning of the Fourth Amendment, even though the purpose of the stop is limited and the resulting detention is quite brief. Delaware v. Prouse, 440 U.S. 648, 653 (1979). See also United States v. Brigham, 382 F.3d 500, 506 (5th Cir. 2004) (en banc); Francis v. Smith, 922 S.W.2d 176, 178 (Tex.Crim.App. 1996).
Law enforcement officers may stop and briefly detain persons suspected of criminal activity on less information than is constitutionally required for probable cause to arrest. Terry v. Ohio, 392 U.S. 1, 22 (1968). Because a routine traffic stop is more analogous to an investigative detention than a custodial arrest, traffic stops are analyzed as Terry stops. Berkemer v. McCarty, 468 U.S. 420, 439 (1984); United States v. Brigham, 382 F.3d 500, 506 (5th Cir. 2004) (en banc).
Both the driver and any passengers are considered seized within the meaning of the Fourth Amendment and may challenge the legality of the stop and the length and scope of their detention. Brendlin v. California, 551 U.S. 249 (2007).
Under Terry, the court must determine the reasonableness of the search or seizure by asking (1) whether the officer’s action was justified at its inception; and (2) whether the officer’s action was reasonably related in scope to the circumstances which justified the interference in the first place. Terry at 392 U.S. 19. In the context of a traffic stop, obtaining identification, registration, and insurance papers, running warrant checks, and asking questions of the driver regarding his travel itinerary are all reasonably related to the reason for the stop. United States v. Shabazz, 993 F.2d 431, 435 (5th Cir. 1993).
“Once the purpose of a valid traffic stop has been completed and an officer’s initial suspicions have been verified or dispelled, the detention must end unless there is additional reasonable suspicion supported by articulable facts.” United States v. Gonzales, 328 F.3d 755, 758 (5th Cir. 2003) (citing United States v. Machuca-Barrera, 261 F.3d 425, 434 (5th Cir.2001); Shabazz, 993 F.2d at 436). However, “a traffic detention may last as long as is reasonably necessary to effectuate the purpose of the stop, including the resolution of reasonable suspicion, supported by articulable facts within the officer’s professional judgment, that emerges during the stop.” United States v. Brigham, 382 F.3d 500, 512 (5th Cir. 2004) (en banc).