When Veering Out of Your Lane of Travel Leads to a DUI Conviction: Did Police Have Probable Cause to Pull You Over?

If you are a regular reader of this blog, you know that DUI cases can rise and fall based upon police conduct alone, without getting into any issues of driver impairment. So, what happens when police pull over a driver for veering out of his/her lane of travel? Is there probable cause for such a stop, which would allow police to use in court the DUI evidence they recovered?

As with many issues in law, the answer is: It depends. Here’s a case where the Superior Court of Pennsylvania found that police had probable cause to pull over a driver and consequently upheld his DUI conviction.

Crossing Two Lines

In Commonwealth v. Bonawitz, a police officer in a marked cruiser observed a driver on a two-lane road cross over the center line into oncoming traffic. The officer made a U-turn to follow the vehicle and observed it cross over the center line two more times thereafter. In addition, the officer observed the vehicle cross multiple times over the fog line into the shoulder and travel closely beside trees, telephone poles, and a traffic sign. The driver also drove directly on top of the center and fog lines in addition to swerving over them.

All this was captured on motor vehicle recordings from the police cruiser.

The officer stopped the driver for violations of Pennsylvania’s Motor Vehicle Code. He described the driver as “fumbling around, looking for his license, registration, and insurance.” The officer, who was specially trained related to DUIs, observed that the driver had bloodshot, glassy eyes and that an odor of alcohol consistent with intoxication emanated from the vehicle. The driver was asked to submit to field sobriety and preliminary breath tests, and he refused. During the stop, the driver repeatedly asked the officer to contact another police officer who he allegedly knew. The officer indicated that the driver became “defensive and combative” when he asked him about whether he had been drinking that evening. The driver refused to exit his vehicle and instead turned on his cell phone to record the stop.

The officer arrested the driver based on his suspicion that he was unable to operate his vehicle safely due to intoxication. A search of the vehicle revealed three open containers of beer and a cooler with ice and eleven unopened beers on the floor in the front of the car.

The driver was charged with DUI ― general impairment and sought prior to trial to suppress all evidence derived from the traffic stop, arguing that the officer lacked probable cause to stop his vehicle. The trial court refused to suppress the evidence, and the case proceeded to a nonjury trial that same day. The driver was found guilty of the DUI charge.

The driver appealed to the Superior Court of Pennsylvania, again arguing that the officer lacked the requisite probable cause to stop his vehicle and therefore any evidence obtained should have been suppressed.

On Appeal

On appeal, the Superior Court affirmed the lower court’s decision refusing to suppress the DUI evidence.

First, the court noted that Pennsylvania’s Motor Vehicle Code provides that a “vehicle shall be driven as nearly as practicable entirely within a single lane and shall not be moved from the lane until the driver has first ascertained that the movement can be made with safety.”

The court went on to reason that based upon the officer’s observations that the vehicle repeatedly crossed the center and fog lines and the recording that captured the vehicle’s movements, the trial court properly found that the officer had probable cause to stop the driver for violating the statute.

Since the stop was valid, the DUI evidence that it yielded was admissible in court.


Unfortunately for the driver, his conviction will stand. However, it is important to distinguish this case from others where a driver does not repeatedly veer from his/her lane of travel. Notably, in 2016, the Superior Court found that “where a vehicle is driven outside the lane of traffic for just a momentary period of time and in a minor manner, a traffic stop is unwarranted,” and therefore a police officer lacked probable cause.

Query whether this conviction would stand if the officer had only observed the driver veer over the line once before pulling him over.

As always, if you are facing a DUI charge, we recommend that you consult with a qualified DUI attorney immediately to ensure that your legal rights are protected and that you exercise all available defenses.