City Council Faces Renewed Calls to End Use of ShotSpotter

A slate of activists and experts urged the Cambridge City Council on Wednesday to end the city’s use of ShotSpotter, renewing calls to cancel its contract with the gunshot detection system amid concerns about privacy and potential data-sharing with federal authorities.

The Council’s Public Safety Committee convened a panel with the Stop ShotSpotter Coalition Camberville — a group made up of Cambridge and Somerville organizations — along with experts from the American Civil Liberties Union and Boston University.

Cambridge first adopted ShotSpotter in 2014. Since then, activists have repeatedly argued that the technology violates residents’ privacy and risks drawing armed police responses to false alarms. Before Wednesday’s panel, more than 25 residents spoke during public comment in support of the coalition’s demand that Cambridge stop using the system.

The meeting marked the Council’s first public discussion of ShotSpotter since last June.

ShotSpotter uses audio sensors mounted on buildings or streetlights to detect loud, impulsive noises that may be gunfire. When the microphones register a possible gunshot, the system records a short audio clip, runs it through an algorithm to filter out false positives, and alerts local law enforcement with the clip and an estimated location.

But critics say the system can mistake fireworks, backfiring cars, or other loud noises for gunshots — triggering an armed police response even when no gunfire occurred.

In a presentation Wednesday, the Cambridge Police Department said ShotSpotter has verified more gunshots than 911 calls have. Police officials also said officers receive ShotSpotter alerts on their phones, allowing them to respond faster “when seconds can make the difference.”

Still, the city has caught backlash from both residents and councilors who are concerned that the system is constantly collecting audio data, whether the recording is saved and sent to police or not. While the devices are listening for potential gunfire, they only capture recordings when the algorithm deems the sounds to be likely gunfire, functioning similarly to a speech-activated device like an Amazon Alexa.

Stephanie Guirand, presenting on behalf of the Stop ShotSpotter Coalition Camberville, said the system’s constant audio detection has raised “significant concern” among residents. She also questioned the sensitivity of the microphones, arguing that the always-active devices can passively pick up and record conversations on the street.

“Many people didn’t realize that the microphones were always on and continuously listening. So there was widespread belief that the microphones only activated, meaning powered on, once the sound of a gunshot was detected,” Guirand said.

Since the June meeting, Guirand said that The Black Response — a Cambridge-based anti-policing organization — held eight educational workshops and conducted six door-to-door canvassing sessions. Her presentation on Wednesday also included the results of two surveys that TBR conducted to gather resident opinions about the technology.

The online survey the group conducted found, with 10 total respondents, that 90 percent of respondents said their biggest issue with ShotSpotter centered on privacy concerns. The organization also administered a physical survey — garnering nine respondents — during their various sessions, finding that individuals have a skeptical attitude towards the way the devices operate.

Jerome Filip, a spokesperson for ShotSpotter’s parent company, SoundThinking, told councilors on Wednesday that the possibility that the devices — which are placed at high elevations — are listening to conversations at the street level is “extremely improbable.”

Activists also raised concerns about the possibility of data from ShotSpotter’s listening technology being shared with federal immigration enforcement officers.

Spencer Piston, a Boston University political science professor, said ShotSpotter alerts could indirectly increase federal involvement if they lead to arrests. Once a person is booked, he said, their fingerprints are entered into a database accessible to federal agencies, including Immigration and Customs Enforcement.

“Presumably, this has already happened because ShotSpotter alerts have led to arrests, arrests lead to fingerprints, fingerprints are put into the database, and the database is accessible by ICE,” Piston said.

Piston also argued that ICE could potentially obtain Cambridge ShotSpotter data through SoundThinking, which he said owns the data collected by the devices and could legally sell it.

Interim Cambridge Police Commissioner Pauline M. Wells said the city has not received any requests from federal immigration authorities for ShotSpotter data.

“We will not and do not and have not shared information with ICE,” she said.

—Staff writer Shawn A. Boehmer can be reached at [email protected] and on Signal at shawnb.18. Follow him on X @ShawnBoehmer.

—Staff writer Claire A. Michal can be reached at [email protected] and on Signal at ClaireMichal.154.