“Lane Straddling” as the Precursor to a DUI Stop

Posted by Jon Ibanez on April 30th, 2014

In my last post, I mentioned that officers often indicate that the basis for a DUI stop is the observation of a vehicle swerving. Forget about the DUI for a moment. Can the officer initiate a traffic stop for swerving within a lane, often called lane-straddling?

The stopping of a vehicle by law enforcement is a “seizure” and, as such, must adhere to the strictures of the 4th Amendment of the Constitution. The 4th Amendment prohibits unreasonable searches and seizures. To be “reasonable” under the 4th Amendment, the officers must have a reason for the stop. If the officer observes the vehicle violate a traffic law and bases the stop on the violation of the traffic law, the 4th Amendment requirements are usually met.

Is there a traffic law for swerving? Yes.

California Vehicle Code §21658(a), provides, “A vehicle shall be driven as nearly as practical within a single lane and shall not be moved from the lane until such a movement can be made with reasonable safety.”

But what does it mean to drive “as nearly as practical within a single lane?” Does it mean that we cannot have our tires touch the painted lines until we intend on safely merging into an adjacent lane? Fortunately, according to the 9th Circuit Court of Appeals, no.

In U.S. v. Colin, 314 F.3d 439, the 9th Circuit Court of Appeals dealt with this very issue. The arresting officer observed defendant drift onto the solid white fog line of the far side of the right lane for about ten seconds. The defendant’s vehicle then drifted to the left side of the right lane, signaled a lane change, and moved into the left lane. The officer then observed the vehicle drift to the left side of the left lane where its left wheels traveled along the solid yellow line for approximately ten seconds. The defendant’s vehicle then returned to the center of the left lane, signaled a lane change, and moved into the right lane.

Can you picture it?

The arresting officer then pulled the defendant over for possible violations of California Vehicle Code §21658(a) for lane straddling and DUI.

The court held that the officer’s stop was illegal, stating,  “Touching a dividing line, even if a small portion of the body of the car veers into a neighboring lane, satisfies the state’s requirement that that a driver drive as ‘nearly as practical within a single lane’… It is reasonable that a driver with no cars abreast of him might veer slightly within his lane or over the lane lines in the course of making a lane change to ensure that it is safe to do so. In sum, we conclude that the facts, taken together, support the conclusion that [the officer] lacked probable cause to stop [the defendants] for lane straddling.” Id. at 444-445.

It’s good to know that the Court recognizes that we are, after all, just humans who aren’t perfect.

It went on to say, “If a failure to follow a perfect vector down the highway or keeping one’s eyes on the road were sufficient reasons to suspect a person of driving while impaired, a substantial portion of the public would be subject each day to an invasion of their privacy.” Id. at 447.

This is not to say that swerving within a lane cannot be indicative of driving under the influence.

It was articulated in People v. Perez, 221 Cal.Rptr. 776, 778, that “pronounced weaving within a lane provides an officer with reasonable cause to stop a vehicle on suspicion of driving under the influence where such weaving continues for a substantial distance.” (emphasis added).

While officers many times use the observation of swerving and lane straddling as the precursor to a DUI stop, the truth is they often don’t account for simple human error. How often have you inadvertently veered within your lane after a sneeze or while changing the radio station.  The law doesn’t require perfection and neither should officers.

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