ShotSpotter / SoundThinking

Technical capabilities

ShotSpotter (now SoundThinking) deploys arrays of acoustic sensors mounted on city light poles and rooftops, typically at densities of 20 to 25 sensors per square mile. The sensors record audio continuously, with the vendor stating that only sounds resembling gunfire are retained and forwarded to a central operations center where human “reviewers” classify the alert before forwarding to local law enforcement.

Accuracy and false-positive rates are disputed. SoundThinking claims a 97 percent accuracy rate. The City of Chicago Office of Inspector General audit (August 2021) found that only 9.1 percent of ShotSpotter alerts in Chicago produced documented evidence of a gun-related crime. The MacArthur Justice Center analysis of 21 months of Chicago deployments found 89 percent of alerts produced no police report of gun crime.

Documented operational concerns

• Adam Toledo case (March 29, 2021): a Chicago Police Department officer shot and killed 13-year-old Adam Toledo within seconds of arriving at a ShotSpotter alert. Subsequent litigation surfaced concerns about ShotSpotter’s after-the-fact alert reclassification, including in the case of Michael Williams (Chicago, 2020), where alert metadata was reportedly altered post-incident.
• Vice / Motherboard investigation (July 2021): documented that ShotSpotter human reviewers can override sensor classifications and that the vendor has provided altered reports as evidence in criminal proceedings.
• Associated Press investigation (August 2021): confirmed examples of altered alert classification and raised due-process concerns.
• Racial-deployment patterns: MacArthur Justice analysis found ShotSpotter sensors disproportionately placed in Black and Latino neighborhoods, creating differential policing burden.

Customer states

SoundThinking serves approximately 150 to 170 city customers in the United States, plus deployments in Cape Town (South Africa) and Puerto Rico. Public city terminations have accelerated: Atlanta (2022), Charlotte (2023), Pasadena (2023, rejected), San Antonio (2023), Chicago (September 2024). New York City extension is contested in city council debates.

Legal and sanctions status

• Not on the US Department of Commerce Entity List.
• Not designated by US OFAC.
• Subject to ongoing civil litigation including Williams v. City of Chicago (2021) on Brady disclosure obligations.
• Subject to City of Chicago Office of Inspector General audit findings (August 2021).
• Subject to ongoing scrutiny by US Senate Judiciary Committee.

Technical countermeasures

• Community advocacy: city termination is the only durable countermeasure. Atlanta, Chicago, Charlotte, Pasadena outcomes demonstrate that sustained community pressure removes deployments.
• Public-records requests: most US states allow FOIA-equivalent requests for ShotSpotter alert data, false-positive rates, and contract details. Use them.
• Litigation support: defense attorneys facing ShotSpotter-derived evidence should request Brady disclosure of original sensor data and any post-incident classification changes.
• City budget hearings: ShotSpotter contracts are typically renewed in public budget hearings, providing a citizen-comment access point.
• Note: this entry covers a fixed-infrastructure system. Individual technical countermeasures (encrypted messaging, device hygiene, etc.) are not applicable. The defense is collective and political.

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