Supreme Court holds that reasonable mistake of law is excusable. On the morning of April 29, 2009, Sergeant Matt Darisse of the Surry County Sheriff ’s Department sat in his patrol car near Dobson, North Carolina, observing northbound traffic on Interstate 77. Shortly before 8 a.m., a Ford Escort passed by. Darisse thought the driver looked “very stiff and nervous,” so he pulled onto the interstate and began following the Escort. A few miles down the road, the Escort braked as it approached a slower vehicle, but only the left brake light came on. Noting the faulty right brake light, Darisse activated his vehicle’s lights and pulled the Escort over. As a result of the vehicle stop, which lead to a consent search, the driver and passenger were both charged with attempted trafficking of cocaine. They challenged the stop, but plead guilty to drug charges. Full opinion of Supreme Court here. Bottom line: Even if police pull you for the wrong reason like speeding 35 in 25 and the speed limit is actually 45, the stop is probably still legal, if the judge finds the mistake is reasonable. Unless it is a clear violation of your 4th amendment right to privacy. "An officer’s mistaken view that the conduct at issue did not give rise to such a violation—no matter how reasonable—could not change that ultimate conclusion."