574 U.S. 54 (2014)
On the morning of April 29, 2009, Sergeant Matt Darisse of the Surry County Sheriff's Department observed northbound traffic on Interstate 77 near Dobson, North Carolina.1 He followed a Ford Escort whose driver appeared nervous.2 When the Escort braked, only the left brake light illuminated; Darisse noted that the right brake light was not working, activated his vehicle's lights, and pulled the Escort over.3
Two men were in the car: Maynor Javier Vasquez was driving and petitioner Nicholas Brady Heien lay across the rear seat.4 Darisse told Vasquez he would receive only a warning ticket for the broken brake light if the license and registration checked out. After a records check, Darisse issued a warning.5 During the stop, Darisse became suspicious because of the occupants' behavior and inconsistent answers about their destination. After asking for and receiving consent to search the vehicle from Heien, who owned the car, Darisse discovered a bag containing cocaine in a duffle bag.6 Both men were arrested and the State charged Heien with attempted trafficking in cocaine.7
Heien moved to suppress the evidence.8 The trial court denied the motion.9 Heien pleaded guilty but reserved the right to appeal the suppression ruling.10
The North Carolina Court of Appeals reversed the trial court's decision.11 The North Carolina Supreme Court reversed the Court of Appeals' decision.12 The North Carolina courts ultimately upheld the denial of suppression, and the Supreme Court of the United States granted certiorari.13
Whether a police officer's reasonable misunderstanding of the law can give rise to the reasonable suspicion necessary to justify a traffic stop?14
The Fourth Amendment prohibits unreasonable searches and seizures. A traffic stop is a seizure that must be supported by reasonable suspicion.15 Reasonable suspicion arises from the combination of an officer's understanding of the facts and his understanding of the law.16 If an officer is reasonably mistaken about either, the Fourth Amendment addresses whether that belief is objectively reasonable.17
Yes. Sergeant Darisse observed that only the left brake light illuminated on the Ford Escort driven by Vasquez.18 He pulled the vehicle over based on his understanding that the right brake light not working violated North Carolina law.19 The North Carolina statute required a stop lamp and provided that a stop lamp may be incorporated into a unit with one or more other rear lamps.20
The referent other suggests that a stop lamp may be a type of rear lamp, and the statutory scheme had not been previously construed by North Carolina appellate courts.21 Given those features, it was objectively reasonable for Sergeant Darisse to think that a faulty brake light violated state law.22 Because the mistake of law was reasonable, there was reasonable suspicion justifying the stop of the vehicle owned by Heien.23
Because Sergeant Darisse's mistake about North Carolina's brake-light law was objectively reasonable, the stop in this case did not violate the Fourth Amendment.24
Related opinions on this issue
Joined by Justice Ginsburg
Justice Kagan, joined by Justice Ginsburg, concurred because the Court correctly explains that reasonable mistakes of law can support the reasonable suspicion necessary to stop a vehicle under the Fourth Amendment, and that such mistakes must be objectively reasonable.25 An officer's subjective understanding of the law is irrelevant, so the government cannot defend a seizure by pointing to the officer's lack of training or reliance on an incorrect memo.26 This inquiry is more demanding than qualified immunity doctrine, which shields officials who are not plainly incompetent or who make reasonable but mistaken judgments about open legal questions.27
To sustain a stop based on a mistake of law, the legal question must be genuinely difficult, so doubtful that reasonable judges could disagree.28 The North Carolina statute's language poses a difficult interpretive question, and Sergeant Darisse's view was a reasonable reading that a court could accept.29
Justice Sotomayor dissented on the ground that the Court's holding departs from the traditional framing of the Fourth Amendment reasonableness inquiry.30 That inquiry evaluates an officer's assessment of the facts against the actual state of the law and does not take the officer's understanding of the law as an input.31 She would hold that a police officer's mistake of law, however reasonable, cannot provide the individualized suspicion necessary to justify a seizure under the Fourth Amendment.32
Our cases discussing reasonable suspicion and probable cause have focused on factual determinations rather than the officer's understanding of legal rules.33 Permitting reasonable mistakes of law to justify seizures erodes Fourth Amendment protections in contexts such as traffic stops.34 The early customs cases and Michigan v. DeFillippo do not justify the conclusion because they arose from distinct statutory schemes or involved enforcement of presumptively valid laws.35