Background
On January 21, 2024, Aberdeen Police Officer Brady Woehl stopped Nathan Hawley after observing him come to a complete stop at a stop sign, activate his right turn signal, and then turn right. Officer Woehl believed Hawley violated SDCL 32-26-18.1 by failing to activate his turn signal for a continuous 100 feet before turning. The stop led to a DUI investigation, Hawley’s arrest, and a blood draw revealing a blood alcohol concentration of .197%.
Hawley moved to suppress all evidence, arguing the stop violated the Fourth Amendment because Officer Woehl misread the turn-signal statutes. He pointed out that SDCL 32-26-18.1 requires a signal only “when required,” and that SDCL 32-26-22 makes a signal required only when the operation of another vehicle “may be affected” by the turn—a circumstance the State never established. Officer Woehl testified he was unfamiliar with SDCL 32-26-22 and believed a 100-foot turn signal was required before every turn, without exception.
The magistrate court denied suppression, finding the statute unambiguous and the stop lawful. After a court trial on stipulated facts, Hawley was convicted of DUI. The circuit court affirmed, reasoning that even speculative possibilities—such as a trailing vehicle that might have been speeding, or unseen pedestrians in a residential area—satisfied the “may be affected” condition. Hawley appealed to the South Dakota Supreme Court.
The Court’s Holding
The Supreme Court reversed unanimously on the merits. Reading SDCL 32-26-18.1 and 32-26-22 together, the Court held that a turn signal is not required in every instance; the “when required” language in SDCL 32-26-18.1 would be rendered surplusage under the officer’s all-circumstances interpretation. SDCL 32-26-22 supplies the triggering condition: a signal is required only when the operation of another vehicle “may be affected” by the turn. The Court relied on its 1993 decision in State v. Eidahl, which had reached the same statutory construction, and noted that precedent is a relevant factor in assessing whether an officer’s mistake of law is objectively reasonable.
The Court found that the circuit court’s attempt to satisfy SDCL 32-26-22 rested on hypothetical scenarios—speeding drivers, unseen pedestrians—that were unsupported by any evidence in the record or the parties’ stipulated facts. The only vehicle the record placed in the vicinity was Officer Woehl’s patrol car, traveling about one block behind Hawley, and there was no testimony that even that vehicle may have been affected by the turn. Officer Woehl’s belief that a signal was always required was therefore an objectively unreasonable mistake of law, and the stop lacked reasonable suspicion.
The Court remanded for further proceedings consistent with its opinion. Justice Salter concurred specially to note that an officer’s observation of a traffic violation actually supplies probable cause—a higher standard than reasonable suspicion—but agreed the distinction was immaterial here because the stop failed constitutional scrutiny under either standard given the unreasonable mistake of law.
Key Takeaways
- South Dakota’s turn-signal statutes (SDCL 32-26-18.1 and 32-26-22) do not require a signal before every turn; a signal is required only when another vehicle’s operation “may be affected” by the movement, and that condition must be supported by actual facts, not speculation.
- An officer’s objectively unreasonable mistake of law cannot supply reasonable suspicion or probable cause for a traffic stop, even if the officer acted in subjective good faith; officers are obligated to understand the laws they enforce at an objectively reasonable level.
- Courts may not supply the factual predicate for a traffic stop by hypothesizing scenarios not in the record; Fourth Amendment analysis must rest on the evidence actually presented.
- Prior judicial interpretations of a statute—here, Eidahl‘s reading of SDCL 32-26-22—are a relevant factor weighing against a finding that an officer’s contrary interpretation was objectively reasonable.
Why It Matters
This decision reinforces the limits of the Heien v. North Carolina mistake-of-law doctrine in South Dakota. While Heien permits stops grounded in reasonable mistakes of law, Hawley makes clear that the leeway is narrow: where the relevant statutes are unambiguous and existing precedent directly contradicts an officer’s interpretation, the mistake will not be deemed reasonable. Defense counsel in DUI and other traffic-stop cases should closely scrutinize whether the specific statutory predicate cited by an officer was actually satisfied on the facts of record.
The decision also illustrates a recurring tension in multi-statute traffic codes: an enforcement statute (SDCL 32-26-18.1) that contains a “when required” qualifier must be read in conjunction with the statute that defines when the requirement is triggered (SDCL 32-26-22). Prosecutors cannot rely on officers’ incomplete knowledge of interlocking statutes to shore up a stop after the fact with hypothetical facts never established at the suppression hearing.