The Cambridge Public Safety Committee held a hearing on the police department’s use of SoundThinking, formerly ShotSpotter, on June 2. The gunshot detection system, used in both Cambridge and Somerville, has recently drawn criticism from residents — particularly because both cities are sanctuary cities.
Residents who spoke at the meeting criticized the technology as a form of mass surveillance and questioned its effectiveness.
“I don’t trust the ShotSpotter technology to be doing what the representative claims that it does,” Danforth Nicholas, a community member, said during the meeting. “This is not public safety. This is undisclosed surveillance.”
Critics warn that because SoundThinking devices record continuously and can capture conversations, they pose a risk of misuse. Spencer Piston, professor of political science and director of advanced programs at Boston University, cited Paul Greene, a customer support engineer who testified under oath in a Massachusetts case in 2015 about SoundThinking’s recording capabilities.
“ShotSpotter centers record 24 hours a day, seven days a week. A conversation at a normal volume may be recorded by a sensor up to 50 feet away, ” Piston said, recalling the testimony. “In effect, the listening to conversations is continual.”
For some, this is especially troubling because SoundThinking is not funded by the cities of Somerville and Cambridge, but by the Department of Homeland Security, which oversees Immigration and Customs Enforcement.
“We know that ICE and DHS, more broadly, are trying very hard to upgrade their capacity,” Piston said. “So, from a sanctuary city perspective, it might not be the best idea to build a surveillance state for them.”
Although the company shares only brief audio clips — captured a few seconds before and after a detected gunshot — and only with the police departments in Somerville and Cambridge, there are no clear safeguards to prevent the broader collection of audio data from being misused.
“The contract language itself says that [SoundThinking] can share data recordings with law enforcement broadly,” Stephanie Guirand, a member of The Black Response and representative of the Camberville Stop ShotSpotter Coalition, said. “So that signals to us that the data, the recordings, are being made available to law enforcement — especially the Department of Homeland Security and ICE.”
Another concern is frequent false alerts, which critics say can lead to over policing in predominantly Black and immigrant neighborhoods where the devices are installed. In Cambridge, around 60% of ShotSpotter activations over the past decade were not confirmed as gunfire.
“This sets the public up for more encounters with police who are coming into their neighborhoods with the assumption that people are armed and dangerous, which can lead to aggressive policing and violence,” Somerville resident Lauren Leon said during the meeting.
While many concerns remain speculative, residents say it is unclear whether the potential benefits of SoundThinking outweigh the risks.
Cambridge Police Commissioner Christine Elow praised the technology for its ability to get police to a scene quickly in the absence of a call to emergency services.
“ShotSpotter has saved a life in our city, and that’s really what I go back to,” Elow said. “We know that police have arrived sooner [to] gunfire where we did not get a 911 call. And that, in and of itself — the fact that we saved a life — feels enough of a reason to keep it.”
While academic literature indicates that SoundThinking improves police response times, claims that it systematically saves lives or reduces gun violence are not similarly proven.
“The issue is that police response times don’t automatically translate into better health outcomes. There’s a lot more that has to happen,” Piston said. “I think it’s a bit too cavalier to say over and over again that ShotSpotter saves lives.”
“ShotSpotter is a technology that’s largely untested by third-party verification methods,” Guirand said. “If it’s not being tested by a third party, then it’s misleading the effectiveness of their tool — and that has been the case generally.”
Unclear evidence of the technology’s effectiveness raises questions about whether it is worth the risks it poses.
“Is it worth giving up your privacy so that we can hear the sound of [gunshots] or have the police arrive two seconds earlier?” Guirand said.
For elected officials, the perspectives of communities affected by gun violence are important in the debate over whether to keep SoundThinking devices in Somerville and Cambridge. While many spoke out at the meeting against the technology, the Cambridge Police reported no complaints related to a ShotSpotter alert over the past 11 years.
Guirand, who holds focus groups on ShotSpotter in immigrant communities, said residents expressed concern about being recorded.
“People were worried that they’re being recorded,” she said. “But they also don’t feel safe publicly coming out to say that they’re against this, because they don’t know what sanctuary status means anymore.”
Cambridge City Councilor Catherine Zusy proposed a pause to the use of SoundThinking technology for the duration of President Donald Trump’s term.
“I wonder if we should take it down, and then once the world returns to a normal, safer place, then consider the idea of resuming use of the technology if we find that there actually is a need for it,” she said.
