Thirty-one states now allow law-enforcement officials to access license photos to help identify potential suspects

By Zusha Elinson

When police in the small Maryland city of Hagerstown used a cutting edge, facial recognition program to track down a robbery suspect last week, it was one of the first such cases to come to light.

In the process of identifying a possible suspect, investigators fed an Instagram photo into the state’s vast facial recognition system, which quickly spit out the driver’s license photo of an individual who was then arrested.

This digital-age crime-solving technique is at the center of a debate between privacy advocates and law-enforcement officials: Should police be able to search troves of driver’s license photos, many who have never been convicted of a crime, with facial recognition software?

An increasing number of police departments across the country are running images through driver’s license databases in their investigations But the Hagerstown case is one of the few resulting in an arrest that has become public, experts in the field say.

Thirty-one states now allow police to access driver’s license photos in facial-recognition searches in addition to mug shots, according to the Center on Privacy and Technology at the Georgetown University Law Center. Roughly one in every two American adults—117 million people—are in the facial-recognition networks used by law enforcement, according to a 2016 report by the center.

Civil liberties advocates say that giving police unfettered access to photos of people who have committed no crimes infringes on their privacy.

“People provide their photo for a driver’s license database so they can drive,” said Jennifer Lynch, an attorney with the Electronic Frontier Foundation, a nonprofit privacy organization. “They should not become suspects in a criminal investigation.”

Law-enforcement officials who advocate for using facial recognition searches of driver’s license photos argue that it is a valuable tool for finding potential suspects who have no criminal past.

“This is no different than if I laid out all those photos in front of me…and said ‘No, that doesn’t look like him, that doesn’t look like him, here we go, that’s him,’ ” said Sheriff Bob Gualtieri of Pinellas County, Fla. “The only thing is I am doing it in a different way, a more automated way, a more efficient way.”

Mr. Gualtieri, who launched a facial recognition system in 2001 that is now used by police around Florida, said that it is not uncommon for investigators to get a match on a driver’s license photo in his state.

In New York City, police say they want to get access to driver’s license photos in their facial-recognition searches, which are currently limited to mug shots, but have faced opposition from privacy advocates.

In Maryland, police use the what they call the Maryland Image Repository System to compare images with more than 7 million driver’s license photos and more than 3 million mug shots.

In a report last December, Stephen Moyer, Maryland Secretary of Public Safety & Correctional Services, assured lawmakers that people’s privacy was being protected.

With the technique now being more widely used across the U.S., Ms. Lynch, of the EFF, said there should be more checks and balances because of the risk of mis-identifying suspects using facial recognition software, which is less accurate with darker faces, according to a recent MIT Media Lab study.

In the Hagerstown case, Raven Dennis reported that a former Dunkin’ Donuts co-worker came to her apartment and allegedly stole her iPhone 8 and $650 last Sunday, according to the police department’s probable cause statement. When she chased after him, the man threatened her with a handgun, she said.

Ms. Dennis told police that she only knew the man’s first name, Aamir, but the two had been in touch on social media, so she sent two Instagram photos to investigators. When a detective ran a screenshot through the state’s facial recognition system, the first image that came back was a Motor Vehicle Administration photo of Aamir Watson-Jones, according to the probable cause statement.

Mr. Watson-Jones was arrested and charged with armed robbery, robbery, theft, and a handgun violation. He has yet to enter a plea.

An attorney for Mr. Watson-Jones and the Hagerstown detective on the case didn’t return calls seeking comment.

Joseph Michael, deputy state’s attorney in Washington County, Md., where the case unfolded, said facial recognition is useful for police, but it can’t be the sole source of identifying a suspect. “You still need a positive identification, as happened in this case,” he said.

Mr. Michael said he understands the privacy concerns, but noted that “the expectation of privacy ends when you sit down and smile at the government desk.”

Write to Zusha Elinson at zusha.elinson@wsj.com