ShotSpotter Community Privacy Protections
Last Updated: July 2019
As technology continues to advance, balancing its benefits against some of its inherent risks to privacy continues to be an issue which confronts us all. What’s true for technology in general is also the case in the realm of public safety. Technological advances have provided significant benefits to those tasked with keeping us safe while at the same time raising appropriate dialogue about how we can leverage those benefits while minimizing unwarranted intrusions on personal privacy.
Several police tools and technologies capture information that is already in public view: license plate readers, video cameras at stoplights and ATMs, combined video/audio surveillance cameras, facial recognition algorithms, etc. Unlike general audio and video surveillance devices, such as the tens of thousands of video cameras deployed in our nation’s cities which monitor general activities, gunshot detection technology is designed to trigger on loud explosive or impulsive sounds that may likely be gunfire and occur only rarely—and that the public already “hears”.
The company takes privacy very seriously and has structured its technology, processes and policies in such a way to minimize risk of privacy infringements while still delivering important public safety benefits.
Independent Privacy Audit
The non-profit Policing Project at the New York University School of Law conducted an independent audit of ShotSpotter’s privacy practices in the spring of 2019. The audit concluded that “the risk of voice surveillance is extremely low.” The report notes that there are important design frameworks and operational safeguards built into how ShotSpotter operates to prevent this from happening.
“While it is surely possible that ShotSpotter sensors will, on occasion, capture some intelligible voice audio related to a gunfire incident, we have little concern that the system will be used for anything approaching voice surveillance…Other policing technology companies should follow ShotSpotter’s leadership and proactively embrace their responsibility to protect individual liberty with their products.” Barry Friedman, Policing Project Faculty Director.
Protections Prior to Activating the System
- When ShotSpotter comes to a new city, we strongly encourage our clients to engage with their communities about the decisions to acquire and use our technology.
- Using a data-driven approach, ShotSpotter works with our clients to determine the geographic area they want covered by ShotSpotter (i.e. the most gun violent areas).
- When the coverage area is set, ShotSpotter engineers determine where to place sensors so as to allow even gunshot detection throughout the area. Police do not determine where to place sensors and do not have access to a database of sensor locations.
- ShotSpotter acoustic sensors are not positioned, tuned or specialized to pick up human voices. The sensors use ordinary microphones that are similar to ones found in cellphones and are placed high above the street.
Before and During an Incident
- Sensors “listen” for gunshot-like sounds and trigger only when detecting an impulsive sound that is instantaneous and sharp. When at least three different sensors detect a gunshot-like sound at the same time and determine a location, they send a short audio snippet to ShotSpotter headquarters.
- Human voices and street noise will never trigger a sensor because they do not produce an instantaneous sharp sound and they are not loud enough to be picked up by three or more sensors.
- Live streaming of sensor audio is not possible by company employees, police or third parties.
- Upon detecting a likely gunshot, trained ShotSpotter personnel listen to a short computer-generated audio snippet of the gunfire to double check that it is actually gunfire.
- It is highly unusual for a human voice to be included in a snippet. For this to occur, the voice must be loud enough to be heard over the gunfire. There is no personally identifiable information in any audio snippet.
- If a snippet is determined to be gunfire, police are notified and provided with the audio snippet that contains the gunfire to better help them understand number, sequence, and caliber of rounds fired.
After an Incident
- If ShotSpotter receives a request (including a subpoena) for additional audio beyond the gunshot snippet, the company has and will continue to fight the request.
- Sensors store 30 hours of audio and automatically delete audio older than 30 hours. Neither police nor third parties ever have direct access to this audio.
- Under strict conditions, ShotSpotter personnel can access this audio ONLY if presented with hard evidence that a gunshot was missed. In this case, company personnel look back at specific portions of the audio to determine if the system picked up the gunshot. If a missed gunshot is found, an audio snippet is provided to police.
- The company made changes to the system around 2012 to prevent access to extended audio.
- ShotSpotter never modifies the audio in any way.
In the end, we believe that the privacy of our communities and social benefits of decreased gun violence are not at odds with each other. Our ultimate goal is to ensure that both are satisfied. We believe we have taken all reasonable and necessary precautions to assure a robust and strong privacy posture. We will continue to review and revise our technology, processes and policies.