Last month, the U.S. Supreme Court decided an interesting case that clarified a question that can come up, even if infrequently, in criminal defense: may police develop reasonable suspicion to stop a vehicle based on a mistake of law? Established case law already holds that an officer is able to develop reasonable suspicion, or probable cause for that matter, based on a reasonable mistake of fact. But does the same principle apply to mistakes of law?
The question came up in connection with a North Carolina case in which a driver had been pulled over after an officer noticed he had a burnt out brake light. During the stop, the officer found drugs and the motorist was subsequently charged with drug trafficking. Although state law doesn’t technically require both brake lights to be in working order, the officer had assumed that having only one working light constituted a violation of the traffic code. As it turns out, that mistaken assumption was deemed to be reasonable, and for that reason the court upheld the stop.