What is the standard of reasonableness in the context of a Fourth Amendment suppression ruling?

We independently review a Fourth Amendment suppression ruling " 'measur[ing] the facts, as found by the trier, against the constitutional standard of reasonableness.' " (People v. Leyba (1981) 29 Cal.3d 591, 597.)

When a vehicle has been lawfully stopped for a traffic violation, the detention "must be temporary and last no longer than is necessary to effectuate the purpose of the stop." (Florida v. Royer (1983) 460 U.S. 491, 500.) "A lawful roadside stop begins when a vehicle is pulled over for investigation of a traffic violation. The temporary seizure of driver and passengers ordinarily continues, and remains reasonable, for the duration of the stop. Normally, the stop ends when the police have no further need to control the scene, and inform the driver and passengers they are free to leave. [Citation.] An officer's inquiries into matters unrelated to the justification for the traffic stop . . . do not convert the encounter into something other than a lawful seizure, so long as those

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