Eric Piza
Professor of Criminology & Criminal Justice, Director of Crime Analysis Initiatives, and Co-
Director of the Crime Prevention Lab, Northeastern University
Key Findings
- In Chicago and Kansas City, as a result of gunshot detection technology (GDT) called
ShotSpotter, police stopped more frequently and closer to the location of reported
gunshots when responding to ShotSpotter alerts than they did to reported gunshots
involving 911 calls. - In both cities, gun recoveries significantly increased in GDT coverage areas, especially
when shootings involved a fatality. - In both cities, GDT had no effect on fatal shootings, non-fatal shootings, or other violent
felonies involving guns, and no effect on rates of gun-violence clearance. - GDT had no effect on shots fired calls for service in Chicago, but reduced these calls in
Kansas City. - These results support prior studies, which have identified a procedural benefit, but not a
prevention benefit, of this type of technology.
Description
Gunshot detection technology (GDT) works through a network of acoustic sensors that detect
sounds from firearm blasts that can be audibly distinguished from other loud noises. GDT
provides a way for law enforcement to respond to shots fired without relying on citizens’ calls
for service, which can be inaccurate and inconsistent. In a new study, researchers measured
changes in gun violence outcomes using a quasi-experimental design with an empirically derived
control group through synthetic control matching techniques to examine the effects of a GDT
program called ShotSpotter in Chicago and Kansas City. In Chicago, police stopped more often
and closer to the location of reported gunfire when responding to ShotSpotter alerts than when
responding to 911 calls, as measured by patrol vehicles’ GPS coordinates. The recovery of illegal
firearms rose in police districts covered by ShotSpotter, particularly at the scenes of fatal
shootings. However, ShotSpotter did not reduce the occurrence of shots-fired calls for service,
fatal shootings, non-fatal shootings or other violent felonies committed with firearms.
ShotSpotter had no impact on gun-violence crime clearance rates (the proportion of cases solved
by police). In Kansas City, the study identified similar findings. Police stopped more often and
closer to the location of the reported gunfire on ShotSpotter runs. The collection of ballistic
evidence and recovery of firearms increased in the ShotSpotter coverage area. While shots-fired
calls for service decreased in the ShotSpotter area of Kansas City, there were no changes in
crime types involving confirmed victims (shootings, robberies, or aggravated assaults), and
ShotSpotter did not improve gun violence clearance rates. The study’s findings align with prior
research, which that has found a procedural benefit, but not a crime-prevention benefit, of GDT.