No Turn-Signal Duty Under Indiana Code § 9-21-8-24 for a Right Turn from a Private Commercial Lot

1. Introduction

In Lanier v. State, the Indiana Supreme Court addressed the boundary between enforceable traffic requirements and an officer’s mistaken understanding of those requirements. The immediate question was narrow: did Indiana Code § 9-21-8-24 require Parnell D. Lanier to signal before turning right from a private gas-station parking lot onto a city street? The broader constitutional question was whether an officer could lawfully stop him for that conduct even if the statute did not prohibit it.

Officer Collin Poynter stopped Lanier after observing the unsignaled turn. During the encounter, the officer smelled marijuana and saw a holstered handgun in Lanier’s lap. The ensuing investigation uncovered marijuana, a digital scale, and, during booking, suspected cocaine. The State charged Lanier with Level 5 felony unlawful carrying of a handgun, Level 5 felony possession of cocaine, and Class A misdemeanor possession of marijuana.

Lanier sought suppression of the drugs and handgun under the Fourth Amendment and Article 1, Section 11 of the Indiana Constitution. He argued that no traffic violation justified the initial stop. The trial court denied suppression, and the Court of Appeals affirmed on reasonable-mistake-of-law grounds.

The Supreme Court reversed. Chief Justice Rush’s opinion, joined by Justices Massa, Goff, and Molter, held that the statute did not require Lanier to signal and that the contrary interpretation was not objectively reasonable. Justice Slaughter dissented, stating that transfer should have been denied and the Court of Appeals’ opinion reinstated.

2. Summary of the Opinion

The Court’s decision rests on four conclusions:

1. The signaling statute did not cover this turn. Lanier neither turned “from a direct course upon a highway” nor changed “from one (1) traffic lane to another.” His movement began in a private commercial parking lot.
2. The statute was unambiguous as applied. Its ordinary language, geographic scope, related provisions, and statutory definitions supported only one reasonable interpretation in these circumstances.
3. The officer’s legal mistake did not justify the stop. Under Heien v. North Carolina, an objectively reasonable mistake about an ambiguous law may support reasonable suspicion. The statutory text here did not reasonably support the officer’s interpretation.
4. Suppression was required on the arguments presented. The State raised no exception to the exclusionary rule. The Court therefore ordered suppression without deciding whether Indiana’s Constitution independently permits reasonable-mistake-of-law stops.

The Court granted transfer, vacated the Court of Appeals’ opinion, reversed the suppression ruling, and remanded with instructions to grant Lanier’s motion and conduct further proceedings. This was an interlocutory suppression appeal, not a determination of guilt or an order dismissing the charges.

3. Legal Reasoning

A. The applicable standards of review

The Court distinguished factual findings from legal conclusions. It deferred to the trial court’s factual findings unless clearly erroneous, considering conflicting evidence favorably to the ruling while also considering substantial, uncontested evidence favorable to Lanier. Statutory interpretation and the constitutional validity of the stop, however, received de novo review.

That distinction mattered because the relevant starting point was undisputed: Lanier began his turn at a private parking-lot exit, not on a highway. The central questions concerned what the statute meant and whether the officer’s contrary interpretation was objectively reasonable.

B. Article 9-21’s geographic scope supplied essential context

Indiana Code § 9-21-1-9 generally limits Article 9-21 to vehicle operation on highways and private roads in residential subdivisions unless another location is specifically identified. A private commercial parking lot falls outside those general categories. A city street, by contrast, falls within the statutory definition of a highway.

The Court did not reason that Article 9-21 could never regulate a vehicle entering from private property. Lanier’s entry onto the city street brought him within the article’s general reach. But geographic coverage alone did not establish a signaling duty: the State still had to show that his movement matched one of the movements described in § 9-21-8-24.

C. Turning “from a direct course upon a highway” requires an existing highway course

The “Direct Course Provision,” § 9-21-8-24(a)(2), concerns turning a vehicle “from a direct course upon a highway.” The Court read the entire phrase rather than isolating the word “upon.” Grammatically, “upon a highway” describes the “direct course” from which the vehicle turns.

Using ordinary meanings, the Court understood a “course” as a path of movement, “direct” as movement without deviation or interruption, and “upon” as “on.” Together, those words identify an existing path along a highway.

Lanier had no such starting course. Although his turn ended on the city street, it began outside the highway. The State’s interpretation focused on the destination of the turn while overlooking the statutory requirement concerning its origin. In ordinary usage, Lanier turned onto the highway rather than from a course already upon it.

D. Related statutes distinguish highway entry from highway travel

The Court reinforced its reading through provisions expressly regulating entry or crossing movements:

• Section 9-21-8-34 requires a driver entering or crossing a highway from a private road or driveway to yield to approaching highway traffic.
• Section 9-21-8-42 addresses vehicles emerging from alleys, driveways, or buildings and requires stopping before entering a sidewalk or its extension.
• Section 9-21-8-45(b) requires a farm-wagon operator to stop before crossing a state highway between fields.

These provisions demonstrate how the legislature identifies movements beginning outside ordinary highway travel. Importantly, the Court did not treat their silence about signaling as conclusive: yielding, stopping, and signaling duties could coexist. The stronger point was linguistic. These statutes expressly describe entering, crossing, or emerging, whereas the Direct Course Provision describes departure from an existing highway course.

E. A commercial parking-lot exit is not a “traffic lane” for this provision

The State alternatively argued that Lanier changed from one traffic lane to another under § 9-21-8-24(a)(3). It suggested that entry and exit lanes at a busy gas station could qualify as traffic lanes.

The Court rejected that interpretation. Ordinary language distinguishes entering a roadway from changing lanes. Statutory context confirms the distinction: “traffic” includes vehicles using highways for travel, and the relevant roadway definition identifies part of a highway used or designed for vehicular travel. Read alongside Article 9-21’s geographic scope, these definitions did not encompass the private commercial exit.

The amount of vehicular activity in the parking lot did not alter its legal character. Lanier entered a highway lane; he did not move from one statutory traffic lane to another.

F. The 2022 amendments did not expand the covered movements

The trial court relied on a case applying former § 9-21-8-25, which required a continuous signal for at least 200 feet before turning or changing lanes. The General Assembly repealed that section in 2022.

The same enactment amended § 9-21-8-24(b) to require signaling before a covered movement regardless of whether another vehicle might be affected. It did not expand the movements listed in subsection (a). Thus, removing the former distance requirement did not establish that every turn, wherever it began, required a signal under the surviving provision.

G. An understandable legal error is not necessarily an objectively reasonable one

The constitutional analysis required a separate step. Establishing that Lanier violated no signaling requirement did not automatically establish that the stop violated the Fourth Amendment. Under Heien v. North Carolina, some objectively reasonable legal mistakes can support reasonable suspicion.

The decisive question was whether the statute reasonably supported the officer’s interpretation. Here, the Court found no such support. Neither the Direct Course Provision nor the Traffic Lane Provision reasonably described Lanier’s movement.

The Court expressly rejected two proposed substitutes for textual support: the absence of an earlier appellate decision addressing this precise turn and the Court of Appeals’ agreement that the officer’s reading was reasonable. Those circumstances can reinforce an interpretation that statutory language already supports; they cannot independently create ambiguity.

This is a demanding, objective standard. It does not turn on an officer’s sincerity, and it is more exacting than the standard applicable to qualified immunity. Nor does the Court’s detailed explanation itself establish ambiguity: explaining why a reading fails is different from identifying two genuinely reasonable readings.

H. Federal suppression supplied complete relief

The officer’s mistaken interpretation supplied the only asserted basis for reasonable suspicion. The stop therefore violated the Fourth Amendment. Because the State invoked no exception to the exclusionary rule, the resulting evidence had to be suppressed.

The Court consequently left the state constitutional issue unresolved. Its ruling neither adopts nor rejects reasonable-mistake-of-law stops under Article 1, Section 11. It also denied as unnecessary Lanier’s request for judicial notice of the Indiana Driver’s Manual.

4. Precedents Cited and Their Influence

A. The principal federal precedent

Heien v. North Carolina, 574 U.S. 54 (2014)

Heien v. North Carolina supplied the controlling Fourth Amendment framework. There, an officer stopped a vehicle because one of two brake lights was not working. Although the governing law was ultimately construed to require only one working brake light, the statutory references to “a stop lamp,” “other rear lamps,” and the maintenance of originally equipped rear lamps reasonably supported the officer’s broader reading.

The precedent therefore permits a stop based on an objectively reasonable legal mistake, not merely a factual mistake. But it also limits that permission: an officer cannot benefit from a “sloppy study of the laws.” The relevant uncertainty must arise from the law itself.

The Indiana Court also found persuasive Justice Kagan’s concurrence, joined by Justice Ginsburg, describing genuinely ambiguous statutes that present “really difficult” or “very hard” interpretive questions. The concurrence’s formulation helped distinguish the narrow category of reasonable legal mistakes from understandable but textually unsupported errors. Unlike the statute in Heien v. North Carolina, Indiana’s provisions supplied no reasonable textual foundation for the asserted violation.

B. The prior Indiana signaling decision

Datzek v. State, 838 N.E.2d 1149 (Ind. Ct. App. 2005), trans. denied

The trial court considered this decision directly on point. The Supreme Court explained why it did not control. Datzek v. State upheld a stop under former § 9-21-8-25. Although it addressed arguments involving §§ 9-21-8-24 and 9-21-8-34, its finding of a violation rested on the subsequently repealed statute, and it did not analyze Article 9-21’s geographic scope.

The Court distinguished rather than expressly overruled the decision. Its significance is that an earlier result involving similar conduct cannot replace analysis of the particular statutory language now governing the stop.

C. Indiana constitutional and review principles

Marshall v. State, 117 N.E.3d 1254 (Ind. 2019)

This decision supplied the suppression-review standard and several constitutional propositions: a traffic stop seizes the occupants; reasonable suspicion requires a particularized, objective basis for believing a traffic violation occurred; and Indiana’s constitutional protection receives independent analysis. It also supplied the state-law requirement that police conduct be reasonable under the totality of the circumstances.

Gary v. State, 276 N.E.3d 639 (Ind. 2026)

The Court cited this case alongside Marshall v. State in identifying the legal questions subject to de novo review, including the constitutional validity of the traffic stop.

Mercado v. State, 200 N.E.3d 463 (Ind. Ct. App. 2022), trans. denied

This case supported the proposition that an objectively reasonable factual mistake can justify a stop under Indiana’s Constitution. Its role was to distinguish an established rule concerning mistaken facts from the unresolved state constitutional treatment of mistaken law.

State v. Keck, 4 N.E.3d 1180 (Ind. 2014)

The Court cited this pre-Heien v. North Carolina decision as having addressed a federal mistake-of-law issue without reaching the state constitutional claim. It also supported leaving the state question unresolved once the federal claim supplied complete relief.

D. Statutory interpretation precedents

Town of Linden v. Birge, 204 N.E.3d 229 (Ind. 2023)

This decision supplied the contextual method: statutory text must be read within its broader statutory scheme. That approach made Article 9-21’s scope and Title 9’s definitions integral to interpreting the signaling provisions.

Fix v. State, 186 N.E.3d 1134 (Ind. 2022)

This case supported ending the interpretive inquiry when contextual analysis yields only one reasonable meaning. It underpinned the conclusion that the statute was unambiguous as applied to Lanier’s turn.

Nardi v. King, 253 N.E.3d 1098 (Ind. 2025)

The Court cited this decision as an example of consulting dictionaries to determine the ordinary meaning of undefined statutory words. That method informed its treatment of “course,” “direct,” and “upon.”

Ruby v. Easton, 207 N.W.2d 10 (Iowa 1973)

This persuasive authority construed “direct course upon a highway” as movement along a straight or curved highway. It reinforced the conclusion that the phrase describes an existing highway path, not entry from a parking lot.

State v. Brown, 81 P.3d 916 (Wash. Ct. App. 2003)

This decision supported the ordinary-language distinction between turning “onto” a highway and turning “upon” it. Its contribution was linguistic support, rather than an independent rule of Indiana constitutional law.

Deal v. United States, 508 U.S. 129 (1993)

This case supported rejecting ambiguity manufactured by selecting alternative dictionary meanings in isolation. Context may resolve a word’s meaning even when a dictionary lists several possibilities.

E. Federal decisions defining the limits of reasonable legal mistakes

United States v. Diaz, 854 F.3d 197 (2d Cir. 2017)

The Court cited this decision as an example of federal appellate application of the demanding limitations described in Justice Kagan’s concurrence in Heien v. North Carolina.

Scott v. City of Albuquerque, 711 F. App’x 871 (10th Cir. 2017)

This decision served the same supporting function: it illustrated judicial application of the requirement for genuine statutory uncertainty, rather than merely an understandable officer error.

United States v. McCullough, 851 F.3d 1194 (11th Cir. 2017)

The Court relied on its express proposition that the presence or absence of an appellate decision is not dispositive of objective reasonableness. This directly answered the State’s reliance on the lack of earlier appellate construction.

United States v. Stanbridge, 813 F.3d 1032 (7th Cir. 2016)

The Court cited this decision when concluding that the officer’s interpretation was not objectively reasonable. It reinforced the limit on using mistaken interpretations of unambiguous traffic requirements to justify stops.

F. Remedy and the vacated intermediate decision

Shotts v. State, 925 N.E.2d 719 (Ind. 2010)

This case supplied the general exclusionary-rule principle that evidence obtained through a Fourth Amendment violation is barred. With no exception asserted by the State, suppression followed.

Lanier v. State, 271 N.E.3d 1185 (Ind. Ct. App. 2025)

The intermediate decision upheld the stop without deciding whether the statute required signaling and adopted a reasonable-mistake-of-law approach under both constitutions. The Supreme Court vacated that opinion on transfer. Its state constitutional analysis therefore does not survive as the controlling resolution of that issue.

5. Impact and Limits

Traffic enforcement must track the particular statutory movement

The decision requires attention to where a vehicle’s movement begins, not simply whether it ends on a highway. Officers and courts cannot treat entry onto a roadway as interchangeable with departure from an existing highway course or a lane change.

The holding is nevertheless specific: § 9-21-8-24 did not require a signal for Lanier’s right turn from a private commercial lot onto a city street. It is not a blanket exemption for every maneuver involving private property. Other statutes may impose yielding, stopping, or additional duties, and residential-subdivision roads receive different treatment under the scope provision.

Mistake-of-law arguments require a textual foundation

For future suppression litigation, the opinion makes the statutory source of uncertainty central. The prosecution must identify language that reasonably supports the mistaken interpretation. Novelty, an officer’s good-faith understanding, or judicial disagreement cannot substitute for that showing.

The state constitutional question remains open

Future litigants may still argue whether Article 1, Section 11 permits stops based on reasonable mistakes of law and, if so, under what conditions. The Court deliberately preserved that question rather than harmonizing Indiana’s Constitution with the Fourth Amendment.

The remedial holding depends on the arguments presented

The Court did not decide that every Fourth Amendment violation necessarily produces suppression regardless of exceptions. Its conclusion expressly depended on the State’s failure to invoke any exception. Likewise, the opinion resolves admissibility, not the ultimate disposition of the criminal charges.

The dissent signals disagreement without explaining its basis

Justice Slaughter would have denied transfer and reinstated the Court of Appeals’ opinion. The supplied text contains no developed dissenting analysis, so it does not establish which aspects of the majority’s statutory or constitutional reasoning he rejected.

6. Complex Concepts Simplified

Reasonable suspicion

A concrete, objective basis for suspecting a legal violation. An officer’s unsupported belief that conduct is prohibited is insufficient.

Mistake of fact versus mistake of law

A factual mistake concerns what happened; a legal mistake concerns what the law prohibits. Lanier’s case involved the latter: the officer observed the conduct but misunderstood its legal significance.

Objectively reasonable mistake of law

An incorrect interpretation that the statutory language genuinely permits a reasonable reader to adopt. Sincerity alone does not satisfy this standard.

Unambiguous as applied

The statute has only one reasonable meaning for the particular circumstances before the court. The Court did not declare that every possible application of § 9-21-8-24 is free from uncertainty.

De novo review

The appellate court decides a legal question independently rather than deferring to the trial court’s interpretation.

Exclusionary rule

A rule generally preventing the prosecution from using evidence obtained through an unconstitutional search or seizure, subject to recognized exceptions.

Interlocutory appeal

An appeal from a ruling made before the case reaches final judgment. Here, the appeal concerned suppression before trial.

Transfer and vacatur

The Indiana Supreme Court accepted review and set aside the Court of Appeals’ opinion, replacing it with its own controlling decision.

7. Conclusion

Lanier v. State establishes that Indiana Code § 9-21-8-24 does not require signaling for the right turn at issue from a private commercial parking lot onto a city street. Because the statute unambiguously excluded that movement, the officer’s contrary interpretation could not justify the stop under the Fourth Amendment.

The opinion’s broader significance is its insistence that reasonable-mistake-of-law doctrine remain anchored in genuine statutory uncertainty. It orders suppression on the record presented while leaving Indiana’s independent constitutional treatment of legal mistakes for another case.