Heien v. North Carolina

Sergeant Matt Darisse stopped a Ford Escort in North Carolina after seeing that only one brake light worked. During the stop, he became suspicious of the occupants' answers and behavior.

The car owner, Nicholas Brady Heien, consented to a search, and officers found cocaine. Later, a court concluded North Carolina law required only one working stop lamp, so the officer had been mistaken about the brake-light law.

The dispute reached the courts because the police action, prosecution, civil-rights claim, or government policy raised a constitutional question that could not be answered by the facts alone.

Can a traffic stop satisfy the Fourth Amendment's reasonable-suspicion requirement when the officer's suspicion rests on a mistaken, but objectively reasonable, understanding of the law?

In plain English, the court had to decide where police authority ended and constitutional protection began under the facts of this case.

Yes. The Supreme Court held that a reasonable mistake of law can support reasonable suspicion under the Fourth Amendment. Because the North Carolina vehicle-code provisions were ambiguous enough to make Sergeant Darisse's mistake objectively reasonable, the stop was lawful.

The decision matters because heien expanded Fourth Amendment doctrine by treating reasonable legal mistakes like reasonable factual mistakes for some investigatory stops. It does not excuse poor legal knowledge; the mistake must be objectively reasonable, not merely sincere.

Police do not have to be legally perfect during a stop, but their legal mistake must be one a reasonable officer could make under an unclear law.

The case matters in traffic-stop litigation, suppression motions, and police training. It encourages courts to distinguish genuinely ambiguous laws from clear statutes that officers simply misread.