WASHINGTON – A police officer can stop a car based on a mistaken understanding of the law without violating the Fourth Amendment, the Supreme Court ruled on Monday in an 8-1 decision.

The case arose from a traffic stop in North Carolina based on a broken brake light. But state law there required only a single working “stop lamp,” which the car in question had.

YOU CAN READ THE PDF HERE:

http://www.supremecourt.gov/opinions/14pdf/13-604_ec8f.pdf

In an opinion by Chief Justice John G. Roberts Jr., the Supreme Court ruled that the officer’s mistake was reasonable and so did not run afoul of the Fourth Amendment’s ban on unreasonable searches and seizures.

The case concerned a 2009 traffic stop near Dobson, N.C., conducted by Sgt. Matt Darisse. The car’s owner, Nicholas B. Heien, who had been asleep in the back seat while a friend drove, consented to a search. Sergeant Darisse found a sandwich bag containing cocaine.

Mr. Heien was charged with attempted drug trafficking, and he challenged the stop as a violation of the Fourth Amendment. A midlevel state appeals court agreed, basing its decision on an interpretation of the state traffic law as requiring only a single working brake light. The interpretation was not challenged as the case was further appealed. The North Carolina Supreme Court nonetheless reversed the decision, saying Sergeant Darisse’s mistake about what the law meant had been reasonable.

In Monday’s decision, Heien v. North Carolina, No. 13-604, the United States Supreme Court agreed. Chief Justice Roberts noted that searches and seizures based on a police officer’s reasonable misunderstanding of the facts had long been permissible. He said that reasoning applied to mistaken interpretations of the law.

Chief Justice Roberts wrote that the court’s decision “does not discourage officers from learning the law,” because only objectively reasonable mistakes were permitted.

“An officer can gain no Fourth Amendment advantage,” the chief justice wrote, “through a sloppy study of the laws he is duty-bound to enforce.”

Justice Elena Kagan joined the majority opinion but added a concurrence, which was joined by Justice Ruth Bader Ginsburg. She emphasized that the state law in question “poses a quite difficult question of interpretation, and Sergeant Darisse’s judgment, although overturned, had much to recommend it.”

Justice Sonia Sotomayor dissented. She said the court’s ruling “means further eroding the Fourth Amendment’s protection of civil liberties in a context where that protection has already been worn down.”

The majority’s approach will also, she said, contribute to distrust between citizens and the police. If police officers are given leeway to interpret the law, she wrote, “one wonders how a citizen seeking to be law-abiding and to structure his or her behavior to avoid these invasive, frightening and humiliating encounters could do so.”

Chief Justice Roberts conceded that the court’s decision at first blush ran afoul of the maxim that “ignorance of the law is no excuse.”

On reflection, he said, the maxim holds the government and its citizens to the same standard where it counts.

“Just as an individual generally cannot escape criminal liability based on a mistaken understanding of the law,” Chief Justice Roberts wrote, “so too the government cannot impose criminal liability based on a mistaken understanding of the law.”