The Supreme Court didn’t buy that argument. “
Authority for the seizure... ends when tasks tied to the traffic infraction are—or reasonably should have been—completed,” wrote Justice Ruth Bader Ginsburg for the majority. The court focused exclusively on the true “mission” of traffic stops—incidentals such as “checking the driver’s license, determining whether there are outstanding warrants against the driver, and inspecting the automobile’s registration and proof of insurance.” All of these things are well and good when the initial stop is valid.
The problem arises when a well-meaning officer turns the traffic inquiry into a prolonged, crime-fighting one. Such unrelated “detours” away from the original traffic mission, the court observed, are unconstitutional without independent, reasonable suspicion that an actual crime has taken place. A cop’s “large hunch” about criminal wrongdoing won’t do.
http://www.newrepublic.com/article/...upreme-court-rules-against-long-traffic-stops