ShotSpotter Study Findings

ShotSpotter creates thousands of dead-end police deployments that find no evidence of actual gunfire

ShotSpotter is a surveillance system that blankets select neighborhoods with microphones and is supposed detect the sound and location of gunfire. ShotSpotter sends alerts of supposed gunfire directly to local police.

ShotSpotter markets this system with a “97% aggregate accuracy rate” but this claim is unsupported by actual evidence. Neither ShotSpotter nor the City of Chicago have ever tested the system to determine just how often it is fooled by loud noises that aren’t gunfire.

The MacArthur Justice Center at Northwestern University School of Law studied ShotSpotter-initiated police deployments from July 1, 2019 through April 14, 2021 to determine whether ShotSpotter’s “accuracy” claims hold up, and to understand the impact of the ShotSpotter system on Chicago’s marginalized communities. The study is based on data obtained under the Illinois Freedom of Information Act in partnership with the Invisible Institute.

We have also created an interactive map of these ShotSpotter alerts and their outcomes across each Ward in Chicago.

Our Key Findings – Dead End Alerts

The overwhelming majority of ShotSpotter alerts turn up nothing.

  • 89% of ShotSpotter deployments in Chicago turned up no gun-related crime
  • 86% led to no report of any crime at all
  • During the 21.5 months we studied, there were more than 40,000 dead-end ShotSpotter deployments
  • On an average day in Chicago, there are more than 61 ShotSpotter-initiated police deployments that turn up no evidence of any crime, let alone gun crime

Discriminatory deployment

The City of Chicago has deployed ShotSpotter in 12 police districts. Those districts are the ones with the highest proportion of Black and Latinx residents in the city. ShotSpotter burdens residents on the South and West sides with thousands of high-intensity deployments where police are hunting for supposed gunfire in vain.

Learn more about the burden on communities of color

There is no good evidence that ShotSpotter can reliably distinguish the sound of gunfire from other loud, impulsive noises.

ShotSpotter has never done a scientifically valid study to determine whether its system can reliably tell the difference between the sound of gunfire and other loud noises like firecrackers, cars backfiring, construction noises, helicopters, and other harmless sounds.

ShotSpotter is a publicly-traded company that provides surveillance technology to law enforcement and other customers. In addition to gunshot detection, ShotSpotter provides so-called “predictive policing” or “patrol management” software and other products. ShotSpotter has contracts with more than 100 police departments.

The City of Chicago is one of ShotSpotter’s two largest customers, accounting for 18% of its annual revenue in 2020.