Do you have to use your turn signal when you pull out of a gas station onto a city street? Under Indiana law, no. And today the Indiana Supreme Court held that a police officer’s mistaken belief otherwise could not justify a traffic stop under the Fourth Amendment to the U.S. Constitution. The Court reversed the denial of a defendant’s motion to suppress the drugs and handgun found after the stop.
The decision matters for two reasons. First, it settles a recurring question about Indiana’s turn-signal statute. Second, and more broadly, it puts real limits on the “reasonable mistake of law” doctrine.
The Stop
In May 2024, Lanier turned right out of a gas station parking lot onto a city street without signaling. An officer parked across the street followed Lanier and initiated a traffic stop for his failure to signal. On approach, the officer smelled the odor of marijuana and saw a handgun in Lanier’s lap. A search of the vehicle and Lanier’s person revealed marijuana, a digital scale, and suspected cocaine.
After being charged with several felonies, Lanier moved to suppress all evidence under both the Fourth Amendment and Article 1, Section 11 of the Indiana Constitution, arguing that no statute required him to signal. At the suppression hearing, the officer cited to Indiana Code section 9-21-8-24 as the basis for the stop. But the officer acknowledged that the statute only required a signal before the driver turned “from a direct course upon a highway,” and the gas station was not a highway.
Nevertheless, the trial court denied the motion. On interlocutory appeal, the Court of Appeals affirmed. The Court of Appeals did not discuss whether the statute required a signal. Instead, its holding rested on the fact that it believed the officer’s reading of the statute was objectively reasonable.
The Statute Did Not Require a Signal
The Supreme Court disagreed. The Court held that the statute was unambiguous, and the plain language made clear that the defendant was not required to signal before exiting a gas station parking lot.
The Reasonable Mistake of Law Doctrine Did Not Save the Stop
The State’s fallback argument was that, even if the officer was wrong, his reading of the law was reasonable. The Supreme Court disagreed, and the important part is how. It expressly adopted the following formulation, taken from Justice Kagan’s Heien v. North Carolina, 574 U.S. 54 (2014): an officer’s mistake of law is reasonable only if the statute was genuinely ambiguous, requiring “hard interpretive work” to overturn the officer’s judgment. Such cases would be exceedingly rare.
Here, the Supreme Court found no comparable textual support for the officer’s interpretation of the statute. Consequently, the evidence should have been suppressed.
The Court declined to decide the Article 1, Section 11 issue because it held that the Fourth Amendment required suppression.