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  • WisBar News
    July 16, 2015

    Supreme Court: Reasonable Mistake of Law Can Support a Traffic Stop

    Joe Forward

    July 16, 2015 – Mistakenly believing that Richard Houghton was violating the law while driving with a missing front license plate and a dangling air freshener and GPS system slightly obstructing his view, police made a traffic stop and uncovered marijuana in a subsequent vehicle search. Recently, the state supreme court upheld the search.

    In State v. Houghton, 2015 WI 79 (July 14, 2015), the Wisconsin Supreme Court ruled (5-2) that police officers can conduct traffic stops with reasonable suspicion that the driver is committing a traffic violation, even if the officer is mistaken about the law.

    That is, “an officer’s objectively reasonable mistake of law may form the basis for a finding of reasonable suspicion,” and “an officer’s reasonable suspicion that a motorist is violating or has violated a traffic law is sufficient for the officer to initiate a stop of the offending vehicle,” Justice David Prosser wrote in a majority opinion of the court.

    Traffic Stop

    In 2012, an East Troy police officer observed a passing vehicle with an air freshener suspended from the rearview mirror. A GPS was also visibly attached to the windshield, and the vehicle, with a Michigan license plate in the rear, was missing the front plate.

    The officer initiated a traffic stop, believing the windshield obstructions and the missing front license plate were violations of Wisconsin motor vehicle laws.

    As he approached the car, the officer smelled marijuana. Upon a vehicle search, the officer found paraphernalia consistent with sales and distribution of drugs, such as plastic baggies, together with a quantity of marijuana nearing 200 grams.

    The state charged Houghton, the driver, with one count of possession with intent to deliver THC (200 to 10000 grams). Houghton filed a motion to suppress the evidence, arguing the officer’s traffic stop and subsequent vehicle search were illegal.

    Specifically, Houghton argued that the officer made an illegal traffic stop because driving without a front license plate or minor viewing obstructions are not violations of state law. Thus, the officer did not have reasonable suspicion to make the stop.

    A circuit court denied the motion, and Houghton pleaded guilty in exchange for the state’s recommendation for lighter sentence. Houghton appealed.

    Obstructed View?

    On appeal, the state conceded that a front license plate is not legally required for all vehicles that drive on Wisconsin roadways. However, the state argued that the dangling air freshener and GPS unit gave the officer a sufficient reason to make the traffic stop.

    The court of appeals reversed, concluding the air freshener and GPS unit did not create probable cause to believe Houghton was violating laws that prohibit drivers from placing objects in vehicles that “obstruct” the driver’s view through the front windshield.

    On appeal to the supreme court, the state argued that the officer was justified in making the stop because Wisconsin driving laws prohibit drivers from suspending or attaching anything from windshields or rearview mirrors, including air fresheners like the one Houghton had suspended from his rearview mirror.

    The supreme court rejected that argument, concluding that not all objects will rise to a level considered an “obstruction.” Wis. Stat section 346.88(3)(b) requires a “material” obstruction, even if minor, to be considered a violation of the statute, the court noted.

    The majority said this case was a close call. But the officer did not violate constitutional protections by conducting a stop for what he believed to be a traffic violation, even if it wasn’t, because police officers can make traffic stops based on a mistake of law.

    Mistakes of Law Allowed

    At the time of the appeals court decision in this case, a similar case was pending before the U.S. Supreme Court, Heinen v. North Carolina. In that case, the court was asked to determine whether an officer’s mistake of law could provide grounds for a traffic stop.

    Ultimately in Heinen, the U.S. Supreme Court ruled that seizures based on an officer’s objectively reasonable mistake of law do not violate protections against unreasonable searches and seizures; reasonable suspicion to stop can be based on an officer’s mistake of law, so long as the officer’s mistake of law was objectively reasonable.

    Justice Prosser noted that prior Wisconsin cases – State v. Brown, 2014 WI 69, 355 Wis. 2d 668, 850 N.W.2d 66 and State v. Longcore, 226 Wis. 2d 1, 594 N.W.2d 412 (Ct. App. 1999), made clear that traffic stops cannot be predicated on a mistake of law.

    The majority explained that states may, under state constitutions, provide more protections to individuals than those provided by the U.S. Constitution and thus, the court was not obligated to follow the U.S. Supreme Court’s holding in Heinen.

    “[W]e have traditionally understood the Wisconsin Constitution’s provision on search and seizure to be coextensive with the Fourth Amendment,” Justice Prosser noted.

    In other words, the majority said it historically follows the U.S. Supreme Court’s Fourth Amendment interpretations on what constitutes an unreasonable search and seizure.

    “Accordingly, we hold that an objectively reasonable mistake of law by a police officer can form the basis for reasonable suspicion to conduct a traffic stop,” Justice Prosser wrote. “All Wisconsin cases holding otherwise are hereby overruled to the extent the conflict with this holding.”

    In this case, although the officer mistakenly believed Wisconsin law prohibited drivers from attaching any nonexempt item to windshields or dangling objects from rearview mirrors, it was an objectively reasonable belief, the majority concluded.

    Finally, the majority noted that it was not objectively reasonable for the officer to believe Houghton’s car needed two license plates, because the car had a Michigan plate.

    In Wisconsin, two plates are required only when two plates are issued, the majority noted, and it would be unreasonable to allow police officers to assume that two plates were issued for an out-of-state car, when the state of origin may only require one.

    “On the other hand, if an officer observes some indicia that a vehicle without a front license plate is from Wisconsin, then the officer may indeed have reasonable suspicion to stop the vehicle,” wrote Justice Prosser, noting Wisconsin issues two license plates.


    Justice Shirley Abrahamson wrote a dissenting opinion, joined by Justice Ann Walsh Bradley. Abrahamson said the Wisconsin Supreme Court should not always defer to the U.S. Supreme Court’s interpretations of the U.S. Constitution as it did here, and she would have reversed the conviction based on the precedent of Longcore and Brown.

    “In the instant case and in many like it, this court is doing what the drafters of the Wisconsin Constitution did not do, namely adopting the federal Bill of Rights,” she wrote. Abrahamson said justices have an oath to support the Wisconsin Constitution, not simply replace the Wisconsin Declaration of Rights with its federal counterpart.

    Related Article

    Supreme Court: Police Traffic Stop Based on Questionable Tail Light was IllegalWisBar News (July 17, 2014)

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