Key Points:

• Arizona Supreme Court rules driving in middle lane can be reason for traffic stop

• Officer had “reasonable suspicion” to stop driver in middle lane, court says

• The ruling sends the case back to a trial judge for further review

The Arizona Supreme Court is providing motorists with a new reason to keep right: Failure to do so can get you stopped and pave the way for a search of your vehicle.

In a unanimous ruling, the justices rejected claims by Asalia Alvarez-Soto that the fact she was driving in the middle lane of Interstate 10 through Pinal County was insufficient reason for Ashton Shewey, an officer with the Department of Public Safety, to pull her over. And once she was pulled over and consented to have a canine sniff around her vehicle, that means the 55 pounds of marijuana found in the trunk of her vehicle was legally seized and could be used as evidence against her.

Of note is that Friday’s ruling is contrary to the one reached a year ago by the state Court of Appeals.

There, a majority of the judges concluded that the stop in this case was an overly strict interpretation of the state’s “stay right” laws.

They said the evidence was that Alvarez-Soto was driving around the speed limit and had not interfered with the flow of traffic. They said the trooper was enforcing the law in a way that could “subject all travelers to virtually random seizures.”

And with the traffic stop not justified, they said the evidence seized could not be used in the criminal case against her.

Friday’s ruling overturns all that.

The case dates to December 2018 when Shewey stopped Alvarez-Soto for violating the statutes that makes it illegal to impede traffic flow by failing to drive in the right lane.

Court records show the stop wasn’t entirely random.

It says Shewey observed the 2007 Chevrolet Malibu, with the trooper later testifying that he knew that drug-trafficking organizations often use Chevy models from 2002 to 2008 as “company vehicles” used to move narcotics out of border cities.

A check of the license plate revealed it was newly registered out of Nogales and recently crossed the international border multiple times. All that, he said, led to his decision to follow the vehicle and, if he saw any traffic violation, pull it over.

While writing her a warning, the trooper asked her about her travel plans and requested her consent to search the vehicle, which she refused.

But she did agree to let Chili, the trooper’s dog, sniff around the vehicle. And when the dog alerted, that led to a search that uncovered the suitcase.

That led to her conviction on charges of possession and transportation of marijuana for sale and a sentence of five years in state prison.

Justice John Lopez, writing for the unanimous Supreme Court, said the key is that the Fourth Amendment to the U.S. Constitution requires only that police have “reasonable suspicion” to stop and briefly detain a vehicle.

That, he said, is determined on the “totality of the circumstances viewed in consideration of the officer’s training and experience.”

In this case, Lopez said, the officer observed the vehicle traveling in the middle lane three miles an hour over the posted 75 mph speed limit over several minutes and several miles. She slowed to 70 mph, at which point another vehicle passed her on the right.

Lopez pointed out that the law requires motorists drive in the right-hand lane if they are going less than the normal speed of traffic. And once Alvarez-Soto slowed to 70 and was passed on the right, he said, that met the “minimal reasonable suspicion threshold.”

He also rejected the argument advanced by the Court of Appeals that interpreting the law that way essentially would force Arizona motorists to violate speeding laws — Alvarez-Soto was driving 78 mph with the flow of traffic — to avoid being pulled over on the “stay right” provision. Lopez said she had multiple opportunities to comply by pulling into the right lane after she was passed on the right.

Lopez acknowledged that a traffic court might reach a different conclusion about whether Alvarez-Soto was violating the traffic law — the reason the trooper said he pulled her over in the first place — something that might require a judge in traffic court to determine whether she was driving at the “normal speed of traffic.” But he said that doesn’t affect the decision of a police officer to stop a motorist in the first place.

“The Fourth Amendment does not require an Arizona officer to interpret every traffic provision with some measure of flexibility before initiating an investigatory stop,” the justice wrote.

“It requires only that the officer have a particularized and objective basis to suspect that a violation may have occurred,” Lopez continued. “An officer’s reasonable mistake about the facts or relevant law does not preclude reasonable suspicion.”

The new ruling does not end the case. Instead, it sends the case back to a trial judge to determine whether the officer unlawfully prolonged the traffic stop.

A 2015 U.S. Supreme Court ruling says that police generally cannot extend a traffic stop beyond the time necessary to deal with the reason for the stop — in this case, a warning for violating the stay right law — unless they have reasonable suspicion that another crime has occurred.