The State of North Carolina (plaintiff) prosecuted Nicholas Brady Heien (defendant) on drug charges related to cocaine that a police officer found in Heien's car. The officer had stopped the car for operating with only one of its two brake lights working. The officer believed this to violate state traffic laws. The trial judge denied Heien's motion to exclude the seized cocaine from evidence. Heien was convicted and appealed to the North Carolina Court of Appeals, which reversed the trial judge's ruling. The appellate court noted that the applicable North Carolina traffic law required only one working brake light, and therefore the police officer's initial traffic stop was unjustified. Without proper justification, the officer's search of Heien's car and seizure of the cocaine violated Heien's Fourth Amendment rights. The state appealed to the North Carolina Supreme Court, which reversed the appellate court on the grounds that the officer reasonably misinterpreted an ambiguously worded traffic law, and therefore a traffic stop based on that misinterpretation was justifiable. On remand, the appellate court affirmed the trial judge's evidentiary ruling. On appeal, the North Carolina Supreme Court affirmed the appellate court judgment. Heien appealed to the United States Supreme Court, which granted certiorari.