State v. Wright, 2010 SD 91

Wright was convicted of possession of marijuana (SDCL 22-42-6) and challenged suppression of evidence from a stop and search.
Trooper Biehl stopped Wright on I-90 after observing Wright’s headlights appear exceptionally bright and allegedly not dimmed as Wright overtook him.
SDCL 32-17-7 requires dimming headlights when meeting or overtaking, but not when being passed by another vehicle; the officer misapplied the statute.
Trial court denied suppression, acknowledging the misinterpretation but finding it objectively reasonable due to the statute being counterintuitive.
The Supreme Court held that the stop was not supported by a proper application of SDCL 32-17-7 and reversed Wright’s conviction.
The case discusses the role of a mistaken belief about the law (mistake of law) in determining the reasonableness of a traffic stop.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the stop was justified by probable cause under SDCL 32-17-7	Wright argued no violation occurred; the stop was predicated on an erroneous interpretation.	Wright contends the officer’s mistake of law cannot justify a stop.	No; the stop lacked valid justification due to an unreasonable mistake of law.
Whether an officer’s objective reasonable mistake of law can justify a stop	The officer’s reasonable belief based on the statute could justify the stop.	Mistake of law cannot provide objective grounds for stop if the law is clear.	No; a clear, unambiguous statute cannot be justified by a mistaken belief; suppression affirmed.
Impact of officer’s subjective belief versus statutory text on Fourth Amendment analysis	The officer acted on good faith misunderstanding of the law.	Objective reasonableness may validate stops despite mistakes.	The officer’s subjective good faith is insufficient when the statute is clear and unambiguous.

State v. Hayen, 2008 S.D. 41, 751 N.W.2d 306 (S.D. 2008) (establishes stopping based on reasonable suspicion for vehicle stops)
State v. Muller, 2005 S.D. 66, 698 N.W.2d 285 (S.D. 2005) (reasonable suspicion standard for traffic stops clarified)
State v. DeLaRosa, 2003 S.D. 18, 657 N.W.2d 683 (S.D. 2003) (probable cause and warrantless searches framework)
State v. Akuba, 2004 S.D. 94, 686 N.W.2d 406 (S.D. 2004) (observations of traffic violations justify stops; legal standards for stop)
Webb v. S.D. Dep’t of Commerce & Reg., 2004 S.D. 63, 680 N.W.2d 661 (S.D. 2004) (officer’s understanding of law not objectively reasonable when unsupported by statute)
Sanders, 196 F.3d 910 (8th Cir. 1999) (officer’s mistake of law can be objectively unreasonable; depends on statutory authority)
Martin, 411 F.3d 998 (8th Cir. 2005) (objective reasonableness of mistake of law; factors include drafting history and prior interpretations)
Washington, 455 F.3d 824 (8th Cir. 2006) (limits of mistake-of-law defense; need for clear statutory basis)
DeGasso, 369 F.3d 1139 (10th Cir. 2004) (addressed reasonable grounds for stops under state law)