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A controversial facial recognition system let police quickly discover the name of a suspect captured after he shot journalists at the Capital Gazette in Annapolis, Maryland, last week, officials said.

"We would have been much longer in identifying and being able to push forward in the investigation without that system," Tim Altomare, Anne Arundel county police chief, said at a press conference June 29. Five people were killed in the shooting.

The suspect was carrying no identification when he was apprehended. Initial attempts to use fingerprints didn't work, as there was a "lag" on the computer system, Altomare said.

So police ran an image of the man through the Maryland Image Repository System (MIRS), which compares photos to millions of driver's license pictures and mug shots.

Despite facial recognition's role in identifying the shooter, critics have questioned the use of the technology. Among other things, they say, it can be inaccurate and the errors can disproportionately affect minorities. It can also threaten civil rights. In 2016, the American Civil Liberties Union criticized Maryland police for using the system to monitor protesters. Still others have said the technology could lead to mass surveillance systems like those used in China.

"It's extremely questionable that the police actually needed facial recognition technology to identify this shooter, who had made multiple prior threats, was in custody and was already fingerprinted," said ACLU Legislative Counsel Neema Singh Guliani. "The public has a right to more answers and an informed debate before any mass surveillance capable technologies, like facial recognition, are acquired or utilized."

Last year, state lawmakers in Maryland debated establishing a task force to study police use of surveillance tech, including facial recognition software.

"We know very little about these systems," said a 2016 report from the Georgetown Law Center on Privacy and Technology. "We don't know how they impact privacy and civil liberties. We don't know how they address accuracy problems. And we don't know how any of these systems -- local, state or federal -- affect racial and ethnic minorities."

Three days before the Maryland shooting, the police department in Orlando, Florida, announced it had stopped using Amazon's widely criticized Rekognition facial identification software.

The MIRS facial recognition technology isn't the only law enforcement system that's been called into question. During his press conference, Altomare lamented the fact that his department can no longer use Geofeedia, which scans social media feeds. That system had also been criticized for its role in monitoring protesters.

First published June 29 at 4:30 p.m. PT.

Update, July 2 at 11:25 a.m. PT: Adds comment from the ACLU.

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