Can a Police Officer Lawfully Pull Over a Car For A Traffic Violation Based on an Erroneous Understanding of the Traffic Laws?

Under Whren v. United States, 517 U.S. 806 (1996), the police can pull over a car based on probable cause to believe a traffic violation has occurred. Any civil traffic violation counts: If you’re driving at 36mph in a 35 mph zone, you can be lawfully pulled over. But what if the officer pulls over a car based on his belief that a violation has occurred, and it turns out that the officer has the law wrong? That is, what if you’re not violating the law, and the officer mistakenly thinks you are? And here’s where it gets interesting: What if the officer’s mistake about the law is a reasonable one?

Lower courts are deeply divided on the question, and the Supreme Court of North Carolina just entered the fray with State v. Heien, ruling by a vote of 4-3 that the Fourth Amendment permits an officer to execute a seizure based on a reasonable mistake of law. The facts of Heien are the best possible facts for the government in a case like this. An officer spotted a car with a broken rear right brake light. The officer pulled over the car, and the traffic stop eventually led to the discovery of drugs in the car. The defendant was convicted, and on appeal persuaded the North Carolina Court of Appeals to adopt a rather surprising interpretation of the traffic laws. According to a long statutory analysis from the North Carolina Court of Appeals, interpreting several archaic sections of the traffic code, it was actually legal to have one broken brake light as long as the other brake light functioned properly. The state government saw the opportunity: It accepted this interpretation of the statutes, and it petitioned the North Carolina Supreme Court only on the Fourth Amendment question of whether the stop was constitutionally reasonable even though it turned out that the officer’s belief that a broken tail light was unlawful was not correct. That is, did pulling over the car with a broken tail light violate the Fourth Amendment?

A divided North Carolina Supreme Court ruled that the stop was constitutionally reasonable. The officer had a reasonable belief as to what the traffic laws meant, the majority reasoned, and he acted reasonably. Because the Fourth Amendment requires reasonableness, this is all the Fourth Amendment requires and the resulting stop was constitutional. The dissent agrees that the officer acted reasonably in a generic sense, but it argues that we would not want to systemically allow stops of people who are not breaking the law at all based on erroneous officer understandings of what the law is. The dissent also points out that this is like an exclusionary rule case in disguise: The majority’s reasoning is akin to saying that there is a good faith exception at the remedies stage, the kind of thinking that should not infuse the court’s reasoning at the initial stage of whether a constitutional violation occurred.

This is a very interesting Fourth Amendment issue — and not an easy one, at least to me. At first blush, my sympathies tend to be with the defense here. That’s true for three reasons, which I’ll concede may be a bit idiosyncratic. First, I’ve always thought that the unstated rationale of why the courts allow a traffic stop for a non-criminal violation must be to enforce the traffic laws — it’s a sort of regulatory rationale which acts as an exception to the usual rule that cause of criminality is required to make a stop. Given that regulatory purpose, it seems sensible that the scope of the police power is based on what that law actually prohibits, not what an officer mistakenly thinks it prohibits. And it doesn’t help that the police tend to have tremendous influence on their state traffic laws: As a practical matter, if an officer can’t find a traffic violation to stop a car, he isn’t trying very hard. And if a court identifies a problem with the traffic laws as the lower court did here, the legislature is likely to fix it in the government’s favor pronto. Given that, I’m not sure why we would need a doctrine that makes room for officer errors of law.

Second, as a Criminal Law professor, I can’t help but approach the question by reference to the doctrine of mistake of law in criminal law. When a citizen makes a reasonable mistake of law as to what is criminal, the general rule is that ignorance of the law is no excuse. If a citizen reads the law and perfectly reasonably thinks his conduct is lawful, only to have a court take a surprising reading of the criminal law and say he is guilty, the courts say “enjoy your time in prison, Mr. Marrero.” And they say that for a good reason. Although it seems harsh in rare cases where the law is construed in a surprising way, we generally want citizens to approach the law with care and have an incentive to learn about it. Looking beyond that one case, it’s very hard to administer routine areas of the law if anyone has an out based on their claim to have reasonably misunderstood it. If we apply that rule to citizens facing the awesome power of the state, it seems only fair to apply the same rule to the state facing its citizens.

Third, I agree with the Heien dissent that this is basically a remedies question under the guise of substantive Fourth Amendment law. If the exclusionary rule is going to be about officer culpability, then say that there is a Fourth Amendment violation here and no exclusionary remedy. But it doesn’t make much sense to harness the same principle to determine what is a Fourth Amendment violation in the first place: If you’re going to draw a sharp rights/remedies distinction, then I think the rationale for the rights and remedies should be kept separate.

With that said, if this case goes up to the U.S. Supreme Court, I highly doubt a majority of the Court would share my initial instincts. If the U.S. Supreme Court takes this case, they will probably see this as an easy case for much of the same reason they saw Davis v. United States as an easy case: The officer acted reasonably based on the law known at the time, so the government should win. They might look at the legal question differently in a case with better facts for the defense, but the facts here would seem to make a government win particularly likely.

And finally, there’s a cynical case to be made that the ultimate outcome may not make much of a difference in the setting of traffic stops. As long as the Whren rule survives that a traffic violation alone justifies a stop, occasional ambiguities in the traffic laws are not likely to interfere much with traffic stops. If the officers can rely on reasonable mistakes of law, then the courts will allow the stops. And if the officers can’t rely on them, the police can go to the legislature and the legislature wil clarify the ambiguities in their favor. Either way, the police have the advantage in cases like this over the long haul so long as Whren is in place.

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