Background
A La Crosse police officer observed a vehicle with darkly tinted rear and rear passenger windows and initiated a traffic stop based on suspected violation of Wisconsin’s window tinting standards. During the stop, the officer observed signs of intoxication and apparent drugs and alcohol in the vehicle. The driver, Michael P. Bundy, was arrested and charged with operating while intoxicated as a third offense. At the time of the stop, the officer used a tint meter that registered 20 percent light transmission through the windows—below Wisconsin’s 35 percent minimum for after-market tinting. However, the windows were factory-installed.
Bundy moved to suppress all evidence from the traffic stop, arguing the officer lacked reasonable suspicion for any equipment violation. The trial court found the windows were legally factory-installed and granted the suppression motion, concluding the stop violated the Fourth Amendment because the officer operated under an incomplete understanding of Wisconsin’s tinting law. Bundy’s vehicle windows did not actually violate any law.
The Court’s Holding
The Wisconsin Court of Appeals affirmed the suppression order. The court held that the officer lacked reasonable suspicion to stop the vehicle because he operated under an objectively unreasonable misinterpretation of Wisconsin’s window tinting statute. Wisconsin law permits factory-installed window tint regardless of opacity, but the officer was not trained to differentiate between factory and after-market tinting. Instead, he assumed all windows must comply with the 35 percent transmission standard.
The court distinguished between two lines of precedent. While general law permits officers to rely on reasonable suspicion without ruling out innocent explanations, a separate line of cases—specifically addressing equipment violations—requires that when a statute creates exceptions based on circumstances, an officer must have particularized suspicion that the vehicle falls into the regulated category. Applying precedents from State v. Houghton (involving a missing front license plate) and State v. Lerdahl (involving a missing brake light), the court found the officer here had no indicia whatsoever that Bundy’s windows were subject to the 35 percent transmission requirement. The officer’s general observation of dark tint cannot support reasonable suspicion when the officer lacks particularized knowledge that the vehicle falls within the class of vehicles subject to that requirement.
Key Takeaways
- Officers cannot rely on objectively unreasonable misinterpretations of equipment violation statutes to establish reasonable suspicion, even when the vehicle actually appears to violate the standard.
- When a statute creates exceptions—such as factory-installed versus after-market tinting—an officer must have particularized suspicion that the vehicle falls into the regulated category, not merely that it appears to violate the regulation.
- Mistakes of law that misunderstand statutory exceptions are constitutionally different from innocent explanations that officers need not rule out under general reasonable suspicion doctrine.
- Lack of officer training on statutory distinctions can establish that a stop rested on an objectively unreasonable legal theory, rendering suppression appropriate.
Why It Matters
This decision reinforces constitutional protections in traffic stops by holding that reasonable suspicion cannot rest on an officer’s fundamental misunderstanding of the law itself. The ruling creates meaningful consequences for law enforcement training: if a statute contains exceptions or categorical distinctions, agencies cannot simply train officers to look for apparent violations without also training them on who is exempt or subject to the regulation. An officer’s ignorance of a statutory exception is not a reasonable basis for a seizure.
The decision is particularly significant for DUI enforcement, where traffic stops based on suspected equipment violations often lead to impaired-driving investigations. By requiring particularized suspicion when exceptions exist, the court has established a check on pretextual traffic stop patterns. The ruling also matters for the window tinting context specifically: the increasing popularity of factory-tinted vehicles means officers cannot stop vehicles based on appearance alone without knowing whether the tint is factory or after-market.