Heien v North Carolina, holding 8-1 that a police officer's reasonable mistake about the law will justify a seizure and not run afoul of the Fourth Amendment. Chief Justice Roberts wrote the opinion for the majority, while Justice Kagan (joined by Justice Ginsburg) wrote a concurring opinion. Justice Soto-Mayor was alone in her dissent.
Heien was traveling on Interstate 77 in North Carolina when Sgt. Matt Darisse of the Surry County Sheriff's Department pulled in behind him because Heien looked "stiff and nervous." Further down the road, Heien braked for slower traffic, and only his left brake light came on. The deputy, believing that he had observed a traffic infraction (a defective brake light) stopped the vehicle. He ultimately ended up searching the vehicle and found a baggie of cocaine. Turns out, the North Carolina motor vehicle code only requires one working brake light, though the statute is somewhat confusing on that issue. Heien moved to suppress the evidence because of the invalid stop.
The trial court denied the motion. The North Carolina Court of Appeals reversed, holding that the motor vehicle code required only one working brake light and, therefore, the deputy's stop of the vehicle was objectively unreasonable. The State appealed and the North Carolina Supreme Court reversed, finding that the statute in question was ambiguous on the issue of the number of brake lights required and that the deputy's decision to stop Heien, though wrong, was nonetheless reasonable.
SCOTUS upheld that decision, noting previous cases where officers who search and seize evidence based on objectively reasonable factual mistakes have been upheld in the past. "The warrantless search of a home, for instance, is reasonable if undertaken with the consent of a resident, and remains lawful when officers obtain the consent of someone who reasonably appears to be but is not in fact a resident. See Illinois v. Rodriguez, 497 U. S. 177, 183–186 (1990). By the same token, if officers with probable cause to arrest a suspect mistakenly arrest an individual matching the suspect’s description, neither the seizure nor an accompanying search of the arrestee would be unlawful. See Hill v. California, 401 U. S. 797, 802–805 (1971)."
The issue was whether an officer is similarly justified when he or she makes a mistake about the law, presumably something they should have the expertise to understand before being allowed to exercise their authority in the community. The majority held that an officer is justified, provided his "mistake" was objectively reasonable. In this case, it was, given the confusing motor vehicle code in North Carolina. Justice Kagan concurred in the result, but wrote separately to highlight the holding that the officer's mistake must not be his subjective belief about what the law is. Therefore, "That means the government cannot defend an officer’s mistaken legal interpretation on the ground that the officer was unaware of or untrained in the law."
Justice Soto-Mayor dissented. Her fear is that interpretations of the law should not be left to police officers in the street. Though officers who make reasonable factual mistakes will be protected, "The same cannot be said about legal exegesis. After all, the meaning of the law is not probabilistic in the same way that factual determinations are. Rather, 'the notion that the law is definite and knowable' sits at the foundation of our legal system. Cheek v. United States, 498 U. S. 192, 199 (1991). And it is courts, not officers, that are in the best position to interpret the laws."