By: Eric L. Piza; George O. Mohler; Jeremy G. Carter; David N. Hatten; Nathan T. Connealy; Rachael Arietti; Jisoo Cho; Emily Castillo

This report presents a study on the impact of gunshot detection technology (GDT) on gun violence. The authors leverage over a decade of data from Kansas City, MO, and Chicago, IL, to measure how GDT contributes to policing and public safety. Both cities installed ShotSpotter GDT systems in 2012, allowing for a long-term quasi-experiment of program effects. Kansas City Police Department installed GDT in October 2012, with the target area covering approximately 3.5 square miles of the city and remaining unchanged to this day. Chicago Police Department installed GDT over approximately 3.0 square miles of the city in August 2012 with the coverage area expanding to 22 additional police districts between February 2017 and May 2018. This expansion led to approximately 100 square miles being covered by GDT in Chicago. The GDT system in Kansas City detected 11,517 gunfire incidents through the end of the study period (12/31/2019). The GDT system in Chicago detected 85,572 gunfire incidents over the full installation period from 2/6/17 – 12/31/19.1 Based upon ShotSpotter’s reported annual subscription costs of between $65,000 and $90,000 per square mile2, GDT coverage costs between $227,500 and $315,000 per year in Kansas City and between $8.8M and $12.3M per year in Chicago.

Final report submitted to the National Institute of Justice, 2023. 114p.

By Jillian Carr

Gunshot detection systems are used by policing agencies across the U.S. to detect incidents of firearms discharge. The most commonly used gunshot detection system is ShotSpotter, currently deployed in more than 100 cities across the U.S.1 Such systems typically use sensors, placed strategically throughout a particular area, to pinpoint the location of gunfire. Agencies that adopt the technology hope that it can help them reduce gun violence and make communities safer. They report that the technology can alert officers to gunshots that otherwise would not be reported, and that it can reduce officer response times by directing them to a more precise location. But the technology can be quite expensive—costing several hundred thousand dollars or more per year to maintain.

We found that in areas of St. Louis County that used ShotSpotter technology, police were alerted to four times as many gunshot incidents during the study period than in comparable areas without the technology. Despite responding to more calls related to gunfire, we found that reported assaults, which include gun-related assaults, fell by roughly 30 percent in areas with ShotSpotter. Moreover, the technology did not produce changes in the number or pattern of arrests. Because we did not find racially disparate effects on the prevalence of crime reporting or arrests from the adoption of the technology, ShotSpotter’s social costs appear minimal.

New York: Policing Project at New York University School of Law, 2021. 18p.