Mistake of Law Doesn't Make Traffic Stop Illegal: Supreme Court

By Brett Snider, Esq. on December 16, 2014 | Last updated on March 21, 2019

Police officers may stop a vehicle based on a misunderstanding of traffic laws without violating the civil rights, the Supreme Court has ruled.

In its 8-1 ruling on Monday, the High Court found that even though a North Carolina police officer misunderstood a state traffic law regarding brake lights, the mistake was reasonable, and thus the search that followed was not illegal. The driver, Nicholas B. Heien, consented to the search of his car following the stop, which yielded a baggie of cocaine.

So why did the Court rule for a search based on a good-faith mistake in Heien v. North Carolina?

'Stop Lamp' Law

The situation in Heien is a familiar one: A car is stopped because of a broken brake light; the officer gets oral consent to search the vehicle and finds drugs. The standard of suspicion necessary to pull a car over for a traffic stop is pretty low -- reasonable suspicion. An officer need only observe a traffic violation to make a legitimate stop of a vehicle.

But what if what the officer thinks is a traffic violation isn't exactly against the law? Heien argued successfully before a North Carolina state appellate court that having one working brake light was enough to satisfy the relevant North Carolina law. The law required that a car be "equipped with a stop lamp," which Heien argued was satisfied by his one working brake light.

Since the car's condition -- based on this interpretation of the "stop lamp" law -- wasn't a traffic violation, Heien argued that the officer had no legitimate basis for stopping the car. Assuming this, the cocaine found as a result of that stop should be excluded as fruit of an illegal stop.

Mistake of Law Can Be Reasonable

The Supreme Court, however, disagreed, finding that police officers could make a reasonable mistake of law and still not violate a suspect's civil rights. After all, the Fourth Amendment permits officers to make reasonable factual mistakes during a reasonable search or seizure, so why wouldn't it allow an officer to a reasonable misunderstanding of the law?

The High Court in Heien notes that the law is often ambiguous, and new advances will make it difficult to determine whether the current law applies (e.g., is a segway a "vehicle"?).

Bottom line: Reasonable mistakes of law can be made without having an investigatory stop violate the Fourth Amendment.

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