Contentious debates over how to reduce gun crime are embedded in Chicago’s political discourse. These debates, however, can stray from the evidence, producing more heat than light. Consider the discussion over the gunshot detection technology ShotSpotter, which was decommissioned in the city on September 23, 2024. The accuracy of the technology, which aims to recognize the sound of gunshots and automatically prompt the deployment of a first responder to the scene, has been put into doubt by numerous organizations. Despite ShotSpotter’s questionable effectiveness, many stakeholders champion the technology as a tool to address gun violence in Chicago – though their enthusiasm seems to go beyond what the current data would support.
The vast majority of gunshots detected by ShotSpotter and followed up by a first responder yield no evidence to confirm that a crime has taken place – no 911 calls, witnesses, victims, or shell casings. Are these ShotSpotter alerts successes, or are they failures, reports of a gunshot that are akin to the ambiguous noise of a tree that may have fallen in an empty forest? The Chicago Police Department (CPD) deems these alerts successful; a ShotSpotter failure, for the CPD, is counted only when the CPD itself reports a mistaken incident to ShotSpotter via email. Using this methodology, the CPD indicated that ShotSpotter had a 99.6% accuracy for identifying gunshots in 2023.
Even accepting the tendentious limitation of “failure” to occasional CPD reports, the CPD inflated the case for ShotSpotter. An investigation revealed the CPD had emailed ShotSpotter 575 times throughout the year to report gunfire misses, exceeding the 205 misses in the agency’s report. The CPD also has misrepresented ShotSpotter’s impact on saving lives in a manner that is favorable to the technology.
When ShotSpotter alerts that don’t produce any supporting evidence are no longer counted as successes, the reliability of ShotSpotter takes on a much less impressive aura. Independent audits conducted by the MacArthur Justice Center and Chicago’s Office of the Inspector General determined an 11% and 9.1% accuracy rating, respectively, for ShotSpotter deployments in the city. These unimpressive numbers are the result of a methodology that treats ShotSpotter alerts without any corroborating evidence as failures, and reflect how the vast majority of ShotSpotter alerts fail to produce any additional confirmation of a gun crime. Detecting a gunshot is a means to the end of combating gun crime; therefore, if alerts do not produce evidence of gunshots, they offer little social value, even if the detection technology is flawless. Technical proficiency and crime control effectiveness are different matters.
Despite the ambiguity or worse surrounding ShotSpotter’s effectiveness, many members of Chicago’s City Council, including 15th Ward Alder Ray Lopez, continue to champion the technology, with Lopez calling it “one of the most effective tools that helps save lives.” A technology diverting significant resources toward reports that do not yield evidence might be quite the opposite of effective. Beyond the resource constraints that ShotSpotter places on Chicago’s first responders – evidenced by a 13% increase in crime scene arrival times after the technology’s implementation – baseless alerts also impose significant consequences on the individuals the system is designed to serve. The lawsuit Williams v. City of Chicago highlights these impacts, showing how ShotSpotter alerts can result in harmful, misplaced suspicion. One of the plaintiffs, Dennis Ortiz, became a target of such suspicion while simply doing his children’s laundry. He was stopped, frisked, and arrested outside of the laundromat, spending the night in jail before the charges against him were dismissed. Ortiz’s experience illustrates the significant consequences that ShotSpotter can impose on individuals who happen to be nearby when a gunshot alert is made.
While ShotSpotter has been decommissioned from the city, the political push to reintegrate the technology has already begun. The Alders debating the technology should be cognizant of the potential to be misled by accuracy statistics, while also considering dimensions such as crime control, police response times, and the potential for innocent Chicago residents to fall under suspicion. By adopting a more critical stance to ShotSpotter, Alders can work toward developing an approach to gun violence that can offer an improved ratio of benefits to costs.