What is the effect of a traffic stop by a police officer on a motor vehicle?

"'"As a general matter, the decision to stop an automobile is reasonable where the police have probable cause to believe that a traffic violation has occurred." [Citation.] If there is a legitimate reason for the stop, the subjective motivation of the officers is irrelevant.' [Citations.] '[T]he law contemplates that the officer may temporarily detain the offender at the scene for the period of time necessary to discharge the duties that he incurs by virtue of the traffic stop.'" (People v. Tully (2012) 54 Cal.4th 952, 980.)

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Officers are permitted to ask about matters unrelated to the traffic stop so long as the questioning does not unduly prolong the stop. (See id. at p. 981; People v. McGaughran (1979) 25 Cal.3d 577, 584.)