Heien v. North Carolina

The driver in this case was stopped by the police because his car had only one working tail light, which the police mistakenly believed was a violation of North Carolina law. The ACLU's amicus brief, submitted with the National Association of Criminal Defense Lawyers and the Cato Institute, argues that a mistake of law can never supply the reasonable suspicion of wrongdoing that the Fourth Amendment requires in order to justify a traffic stop. Ignorance of the law is not an excuse for motorists, and it ought not to be an excuse for the police.