By Alex De Grand, Legal Writer, State Bar of Wisconsin

May 27, 2009 – Even a “momentary” swerve across the centerline of the road can support a traffic stop, the Wisconsin Supreme Court held in State v. Popke, 2009 WI 37.

A police officer had observed Michael Popke’s truck make a left-hand turn onto a cross street at in the early hours of July 8, 2007. The officer saw three-quarters of Popke’s vehicle briefly cross the center of the road immediately after completing the turn. Popke then moved back into the proper lane, but overcompensated and almost hit the curb on the right-hand side of the road. Popke nearly struck the median next, prompting the officer to stop Popke and arrest him. Blood alcohol tests revealed Popke had a blood-alcohol concentration of 0.255 percent.

The circuit court denied Popke’s motion to suppress evidence obtained by the stop, ruling that the officer’s observation of Popke driving on the left side of the road in violation of Wis. Stat. § 346.05 provided probable cause for the traffic stop. If there had not been probable cause for this traffic infraction, the circuit court stated that Popke’s driving would have been sufficient to give the officer a reasonable suspicion that Popke was operating a motor vehicle under the influence. Popke entered a no-contest plea to a charge of operating while intoxicated.

Popke’s appeal

The Wisconsin Court of Appeals reversed the circuit court’s decision, concluding there had been no probable cause to believe a traffic violation had occurred. According to the court of appeals, Popke had not driven down the wrong side of the road within the meaning of Wis. Stat. § 346.05 because he had only crossed the center of the road “momentarily.”

Further, the court of appeals held that Popke’s driving did not give rise to a reasonable suspicion that a traffic or criminal code violation had occurred because it is not uncommon for a motorist to cross the center of the road for so short a time.

Probable cause

Before the supreme court, the state argued that under Wis. Stat. § 346.05, the extent and duration of the crossing of the center is irrelevant.

The state argued that the court should be concerned with the fact that the legislature wrote the statute with several exceptions for when a vehicle may drive in the left lane and not one of them applies to Popke.   Moreover, the state contended that the issue is not whether Popke would actually have been convicted of violating the statute, but whether the police had probable cause to believe a traffic law had been violated.

In its unanimous decision, the supreme court agreed with the state. Citing the police officer’s observations of Popke’s departure from the right-hand lane, the court concluded that the officer had probable cause to believe Popke violated Wis. Stat. § 346.05 and this, in turn, justified the traffic stop.

Probable cause, the court explained, is found with evidence sufficient to lead a reasonable police officer to believe that a traffic violation has occurred. The standard only requires the reasonable officer to believe guilt is more than a possibility, not that guilt is established beyond a reasonable doubt.

The court rejected Popke’s argument that he was not “driving” on the wrong side of the road because he had only fleetingly crossed the center. Defining “drive” to mean “the exercise of physical control over the speed and direction of a motor vehicle while it is in motion,” the court observed that no better word describes Popke’s behavior.

Popke warned that under the state's application of the statute, probable cause arises “if one tread of tire moves over the centerline for even one millisecond.” This enables police to pull over thousands of vehicles every day, Popke argued.

But the justices said this same argument had been rejected in Whren v. United States, 517 U.S. 806 (1996). In Whren, the U.S. Supreme Court said there was no principled basis to say “at what point a code of law becomes so expansive and so commonly violated that infraction itself can no longer be the basis of enforcement.”

Reasonable suspicion

The justices further said that the circuit court correctly believed the police officer would have had reasonable suspicion to conduct an investigatory stop of Popke’s vehicle.

An officer has a reasonable suspicion when specific and articulable facts, taken with their rational inferences, reasonably warrant the intrusion of a stop, the court stated. An inchoate and unparticularized suspicion or hunch cannot be the basis for a reasonable suspicion, the court continued.

Although any one single fact observed by an officer might not be sufficient standing alone to establish a reasonable suspicion, these facts can “accumulate,” the court said. As facts accumulate, reasonable inferences about the cumulative effect can be drawn, the court said.

In this case, the court found that the officer observed several instances of Popke’s erratic driving over the course of approximately one block at 1:30 a.m. The court disagreed with Popke’s argument that the officer’s observations were too few and not detailed enough.