The U.S. Supreme Court issued a 6-3 ruling on April 21, 2015, holding that the police are not permitted to detain a suspect for driving on the shoulder of the road, for even 10 minutes, or otherwise prolong a traffic stop to wait for drug-sniffing dogs to inspect vehicles.
“A police stop exceeding the time needed to handle the matter for which the stop was made violates the Constitution’s shield against unreasonable seizures,” Justice Ruth Bader Ginsburg wrote for the majority.
The matter on appeal concerned a Nebraska police officer witnessing a Mercury Mountaineer driven by Dennys Rodriguez veer onto the shoulder of a state highway just after midnight. The police officer, Morgan Struble, performed a routine traffic stop, questioning Mr. Rodriguez and his passenger and running a records check. The officer then issued Mr. Rodriguez a written warning. That completed the stop, but the LEO noted the presence of air freshener and had his drug-sniffing dog, Floyd, circle the vehicle. Floyd smelled drugs and led his officer to a large bag of methamphetamine. About eight minutes elapsed between the written warning and Floyd’s alert.
Mr. Rodriguez moved to suppress the evidence. SCOTUS held that if an officer can complete traffic-based inquiries expeditiously, then that is the amount of “time reasonably required to complete the stop’s mission.” Hence, a traffic stop “prolonged beyond” that point is “unlawful.”
You can read the entire opinion here: http://www.supremecourt.gov/opinions/14pdf/13-9972_p8k0.pdf