The following is a letter from Stephanie Guirand of The Black Response, a community group of current and former public housing residents concerned with racial justice, police abolition, and surveillance technologies. TBR has developed some good data visualizations of Cambridge’s ShotSpotter deployment here.
Dear Cambridge City Councilors,
I am writing on behalf of The Black Response and the Stop ShotSpotter Coalition – Camberville to thank you for convening a thoughtful and deeply informative Public Safety Committee hearing on ShotSpotter on Monday. We are especially appreciative of Councilor Ayesha Wilson for her skillful facilitation and for managing a logistically complex session with care and focus. We also thank Councilors McGovern, Siddiqui, Sobrinho-Wheeler, Toner, and Zusy for their presence and engagement, as well as Police Commissioner Elow and her colleagues for taking this issue seriously and participating in good faith.
We can all agree that we are in a fight to preserve democracy nationally. At Monday’s hearing, we saw democracy in action. The public, councilors, CPD, researchers, legal experts, and community organizations engaged in meaningful dialogue on a highly consequential issue, ShotSpotter. While we appreciate the opportunity to be heard, several critical concerns raised during the hearing merit follow-up.
ShotSpotter is Always-On and Recording, and Other Privacy Concerns
One of the clearest takeaways from the expert testimony, especially from Professors Spencer Piston and Robert Maher, is that ShotSpotter is a network of microphones that are always on. Regardless of whether audio is stored for 24 or 72 hours, the reality is that these microphones are continuously listening and recording. Whether or not street-level conversation triggers a sensor to send local law enforcement doesn’t matter, the microphones are always listening. Professor Maher affirmed, and Professor Piston supported with legal precedent, that these microphones are capable of picking up and transmitting street-level conversations.
This raises a fundamental difference from personal recording devices (e.g., Smartphones, Alexa), which people knowingly use and control in everyday life. The vast majority of Cambridge residents are unaware of the ShotSpotter microphones. They do not know that they may be recorded while speaking outside or near these microphones. That lack of informed consent raises serious privacy and civil liberties concerns.
The Overstated Utility of ShotSpotter for Law Enforcement
During the hearing, we repeatedly heard from councilors, the police, SoundThinking representatives, and the District Attorney that ShotSpotter is “just one tool among many” used to address gun crime in the city. Police Commissioner Elow opened her remarks by assuring the public that “no one has been arrested solely on the basis of ShotSpotter” (or something to that effect). However, this reassurance raises important questions about the actual utility of the ShotSpotter microphones.
Interpretations of current research (see Carr et al) suggest the presence of ShotSpotter may actually discourage members of the public from calling 911, undermining one of the most direct and community-driven tools for emergency response and investigation.
The data presented by the Cambridge Police Department did not demonstrate a clear or urgent need for ShotSpotter’s microphone technology. Despite the privacy concerns it raises, the numbers failed to show a meaningful impact on reducing gun violence or increasing arrest or conviction rates for gun-related offenses.
Additionally, attorney Connie Tran provided important clarification during the hearing. She debunked a misleading description of a case in which she represented a client who was falsely accused, and ultimately cleared, of gun charges that had originated from a ShotSpotter alert. Tran also noted that the Massachusetts Supreme Judicial Court has raised concerns about the scientific reliability of ShotSpotter and is now requiring courts to evaluate the soundness of ShotSpotter in relevant cases.
If ShotSpotter does not meaningfully reduce gun violence, does not lead to arrests or convictions, and is increasingly under judicial scrutiny for its lack of scientific reliability, we are left wondering: What is its true utility in Cambridge?
Potential Infringement on Civil Liberties of Cambridge Residents
One of the most striking themes to emerge during the hearing, and repeated during public comment, was the tension between the public’s right to privacy and the City’s use of ShotSpotter. At its core, this is more than a debate about a surveillance tool. It is a question of what we value as a community. Should residents be asked to give up their right to privacy in exchange for a law enforcement tool that has demonstrated limited effectiveness?
As experts explained during the hearing, ShotSpotter relies on microphones that are always on and continuously listening. While SoundThinking claims that recordings are only retained for 24 hours (previously 72 hours), the fact remains that these devices are always active in public spaces. Again, most people do not realize that their conversations on the street could be recorded without their knowledge or consent.
The benefits presented by law enforcement were modest at best. In eleven years, ShotSpotter was credited with saving one life in Cambridge. It was unclear whether that incident was also reported through a 911 call. In another instance, there was a confirmed gun incident without a 911 report. It is still not clear if these are two separate cases or the same one. Even if they are different, the impact of ShotSpotter over a decade appears limited.
Despite this, law enforcement and the District Attorney argued that ShotSpotter is a valuable tool beyond its intended function, to identify audio of gun incidents and alert law enforcement to the location of the gun incident. They described instances in which alerts led to broader investigations. For example, in a case discussed at the hearing, a ShotSpotter alert ultimately resulted in a conviction for a restraining order violation, but the person was acquitted of all gun-related charges. This was attorney Connie Tran’s case. While public safety is of course important, using ShotSpotter to extend the reach of investigations raises serious concerns. This pattern suggests that the tool is being used in ways not originally intended, scientifically investigated, or publicly debated.
Professor Spencer Piston raised a similar issue when discussing a class-action lawsuit in Chicago (William v City of Chicago). In that case, plaintiffs argue that ShotSpotter has led to increased policing, stop and frisk, in Black and Brown neighborhoods. They claim that the technology results in over-surveillance and unnecessary police encounters, often unrelated to gun violence. This pattern of overreach is at the heart of their legal challenge.
If local authorities are already stretching the use of ShotSpotter, there is reason to question whether the company itself, or its funders, might also be doing so. In this case, ShotSpotter is funded not by the City of Cambridge, but by the Department of Homeland Security. That funding relationship, between SoundThinking and the Department of Homeland Security, calls into question who truly controls the ShotSpotter technology (and the data it produces) in Cambridge. If the federal government is the real client, what assurances does the City of Cambridge have about how the data is being used or shared?
Without a clear and publicly available contract, it is difficult to verify what protections exist. The City of Cambridge cannot simply rely on verbal assurances from the SoundThinking salesman, or as a Cambridge police officer referred to him, “their colleague.” As attorney Connie Tran points out, the SoundThinking representative during the trial was under oath, and it was there that more information about the function of ShotSpotter was revealed. There must be enforceable limits, transparency, and oversight. The presence of always-on microphones in public spaces, especially without widespread awareness or consent, raises fundamental questions about civil liberties. If the benefits are so limited, is the trade-off worth it?
Cambridge must ask whether this is a reasonable and responsible use of public space and public trust to continue to use ShotSpotter microphones. If not, then it is time to reconsider whether ShotSpotter belongs in our city at all.
Lack of Contract Oversight
We were deeply alarmed to learn during the hearing that the City Solicitor has not yet seen or reviewed the contract that governs the relationship between the City of Cambridge and SoundThinking. The City has a duty to ensure that its agreements, particularly those involving surveillance technologies, are transparent, legally sound, and in compliance with Cambridge’s Surveillance Technology Ordinance.
We strongly urge the Council to:
- Immediately obtain the full contract with SoundThinking,
- Make the document publicly accessible, and
- Schedule a follow-up hearing focused specifically on the contract and its legal implications.
Federal Influence and Sanctuary City Values
Although SoundThinking’s sales representative, Alfred Lewers, claimed that Cambridge data is only shared with the City of Cambridge, the fact that the Department of Homeland Security funds the ShotSpotter system casts serious doubt on that assurance, especially given SoundThinking’s unrestricted ability to share data as established in their contracts (see available contract with Boston). It appears that DHS, not the City, is the true client. We understand this because the City does not appear to even have the contract between the City and SoundThinking. This suggests that SoundThinking has no obligation to uphold Cambridge’s Sanctuary City protections, and the public has no way of verifying who else may access these recordings or how the data is ultimately used.
This raises an important question: if, under the current federal administration, our Sanctuary City status limits federal funding for social programs, why is DHS funding a surveillance system in our city and why is the City of Cambridge working to set it up for them? What does that say about the federal government’s priorities—and about our own?
Lack of Transparency on Device Locations
SoundThinking’s explanation for why device locations are withheld from the public was underwhelming at best. Fortunately, our coalition obtained a leaked list of ShotSpotter microphone locations, which we have since verified by physically visiting the sites. These microphones are disproportionately located on top of public buildings, including public housing and section 8 buildings, confirming that marginalized communities are bearing the brunt of this audio surveillance (see our map).
At the hearing, SoundThinking introduced a paid “dashboard” service that visualizes ShotSpotter data. We see no justification for Cambridge to spend any taxpayer dollars on this, especially when a free and equally effective alternative already exists. In preparation for the hearing, The Black Response developed a publicly accessible dashboard using data from Cambridge’s Bridgestats reports. We offer our dashboard to the city for free (The Black Response’s ShotSpotter data dashboard). If the city does not trust our dashboard, why not contract out this work to other local community organizations or universities in the City?
Incomplete Participation and Need for Follow-Up
Due to time constraints, two of our expert panelists, Jonathan Manes from the MacArthur Justice Center and Abdul Nasser Rad, a quantitative researcher from Campaign Zero, were not able to share their insights during the hearing. In addition, at least a dozen residents who signed up for public comment were not called upon.
We believe a follow-up session is necessary to allow for these important voices to be heard and for unanswered questions to be addressed. We would be more than willing to help coordinate that effort in partnership with the City.
A Call for a Temporary Freeze
We also want to echo the concern raised by Councilor Zusy: perhaps it is time to consider a (temporary) freeze on the use of ShotSpotter in Cambridge. This would be a prudent and responsible step while the City investigates the legal, ethical, and operational implications of ShotSpotter microphones. In an era where federal law enforcement agencies have demonstrated increasing disregard for legal norms and human rights, we cannot afford to take these risks lightly, especially in communities that are already vulnerable.
Thank you again for your leadership and for demonstrating what democratic governance should look like: accessible, informed, transparent, and responsive. We look forward to continuing this vital conversation and working with the City to ensure public safety strategies are both effective and equitable.
In community,
Stephanie Guirand
The Black Response
On behalf of the Stop ShotSpotter Coalition – Camberville