By Kate Conger, Richard Fausset and Serge F. Kovaleski

New York Times News Service

SAN FRANCISCO — San Francisco, long at the heart of the technology revolution, took a stand against potential abuse on Tuesday by banning the use of facial recognition software by the police and other agencies.

The action, which came in an 8-1 vote by the Board of Supervisors, makes San Francisco the first major American city to block a tool that many police forces are turning to in the search for both small-time criminal suspects and perpetrators of mass carnage.

Authorities used the technology to help identify the suspect in the mass shooting at an Annapolis, Maryland, newspaper last June. But civil liberties groups have expressed unease about the technology’s potential abuse by government amid fears that it may shove the United States in the direction of an overly oppressive surveillance state.

Aaron Peskin, the city supervisor who sponsored the bill, said that it sent a particularly strong message to the nation, coming from a city transformed by tech.

“I think part of San Francisco being the real and perceived headquarters for all things tech also comes with a responsibility for its local legislators,” Peskin said. “We have an outsize responsibility to regulate the excesses of technology precisely because they are headquartered here.”

Critics said that rather than focusing on bans, the city should find ways to craft regulations that acknowledge the usefulness of face recognition. “It is ridiculous to deny the value of this technology in securing airports and border installations,” said Jonathan Turley, a constitutional law expert at George Washington University. “It is hard to deny that there is a public safety value to this technology.”

There will be an obligatory second vote next week, but it is seen as a formality.

Similar bans are under consideration in Oakland, California, and in Somerville, Massachusetts, outside of Boston. In Massachusetts, a bill in the state Legislature would put a moratorium on facial recognition and other remote biometric surveillance systems. On Capitol Hill, a bill introduced last month would ban users of commercial face recognition technology from collecting and sharing data for identifying or tracking consumers without their consent, although it does not address the government’s uses of the technology.

Matt Cagle, a lawyer with the ACLU of Northern California, on Tuesday summed up the broad concerns of facial recognition: The technology, he said, “provides government with unprecedented power to track people going about their daily lives. That’s incompatible with a healthy democracy.”

The San Francisco proposal, he added, “is really forward-­looking and looks to prevent the unleashing of this dangerous technology against the public.”

In one form or another, facial recognition is already being used in many American airports and big stadiums, and by a number of other police departments. The pop star Taylor Swift has reportedly incorporated the technology at one of her shows, using it to help identify stalkers.

The facial recognition fight in San Francisco is largely theoretical — the Police Department does not currently deploy such technology, and it is only in use at the international airport and ports that are under federal jurisdiction and are not impacted by the legislation.

Some local homeless shelters use biometric finger scans and photos to track shelter usage, said Jennifer Friedenbach, the executive director of the Coalition on Homelessness. The practice has driven migrant residents away from the shelters, she said.

It has been a particularly charged topic in a city with a rich history of incubating ­dissent and individual liberties, but one that has also suffered lately from high rates of property crime.

The ban prohibits city agencies from using facial recognition technology, or information gleaned from external systems that use the technology. It is part of a larger legislative package devised to govern the use of surveillance technologies in the city that requires local agencies to create policies controlling their use of these tools. There are some exemptions, including one that would give prosecutors a way out if the transparency requirements might interfere with their investigations.

Still, the San Francisco Police Officers Association, an officers’ union, said the ban would hinder their members’ efforts to investigate crime.

“Although we understand that it’s not a 100 percent accurate technology yet, it’s still evolving,” said Tony Montoya, the president of the association. “I think it has been successful in at least providing leads to criminal investigators.”

Cagle and other experts said that it was difficult to know exactly how ­widespread the technology was in the United States. “Basically, governments and companies have been very secretive about where it’s being used, so the public is largely in the dark about the state of play,” he said.

But Dave Maass, the senior investigative researcher at the Electronic Frontier Foundation, offered a partial list of police departments that he said used the technology, including Las Vegas; San Diego: New York City; Boston; Detroit; Durham, North Carolina; Orlando, Florida; and San Jose, California.

Other users, Maass said, include the Colorado Department of Public Safety, the Pinellas County Sheriff’s Office in Florida, the California Department of Justice and the Virginia State Police.

Some experts fear technological advances are outstripping government’s ability to set guardrails to protect privacy. Cagle and others said that a worst-case scenario already exists in China, where facial recognition is used to keep close tabs on the Uighurs, a largely Muslim minority, and is being integrated into a national digital panopticon system powered by roughly 200 million surveillance cameras.

American civil liberties advocates warn that the ability of facial surveillance to identify people at a distance, or online, without their knowledge or consent presents unique risks — threatening Americans’ ability to freely attend political protests or simply go about their business anonymously in public. Last year, Bradford L. Smith, the president of Microsoft, warned that the technology was too risky for companies to police on their own and asked Congress to oversee its use.

23214064