Our latest Public Safety section report concludes that the Chicago Police Department’s (CPD) responses to ShotSpotter alerts can seldom be shown to lead to investigatory stops which might have investigative value and rarely produce evidence of a gun-related crime. We also identified evidence that the introduction of ShotSpotter technology in Chicago has changed the way some CPD members perceive and interact with individuals present in areas with frequent ShotSpotter alerts.
#ShotSpotter is a gunshot detection system that uses a network of acoustic sensors to identify and locate suspected gunshots. Chicago’s $33M, three-year contract with ShotSpotter began in August 2018; in December 2020, well before the end of the contract term, the City exercised an option to extend the contract, setting a new expiration date for August 2023.
OIG analyzed data between January 1, 2020 - May 31, 2021, which found that:
• A total of 50,176 ShotSpotter alerts were confirmed as probable gunshots, each of these resulted in a CPD response to the location. Of these, 41,830 report a disposition—the outcome of the police response to an incident. Of those, a total of 4,556 (or 9.1%) indicate evidence of a gun-related criminal offense
• Through a separate keyword search analysis of all investigatory stop report narratives within the analysis period, OIG identified an additional 1,366 investigatory stops potentially associated with ShotSpotter alerts whose event number did not match any of the 50,176 confirmed and dispatched ShotSpotter alerts.
• OIG’s analysis of ISR narratives further revealed that the presence of the technology is changing police behavior. Specifically, OIG reviewed instances in which CPD members rely, at least in part, on a perceived aggregate frequency of ShotSpotter alerts in an area to form the basis for a stop or as part of the rationale for a pat down once a stop has been initiated.
“Our study of ShotSpotter data is not about technological accuracy, it’s about operational value,” said Deputy Inspector General for Public Safety Deborah Witzburg. “If the Department is to continue to invest in technology which sends CPD members into potentially dangerous situations with little information––and about which there are important community concerns–– it should be able to demonstrate the benefit of its use in combatting violent crime. The data we analyzed plainly doesn’t do that. Meanwhile, the very presence of this technology is changing the way CPD members interact with members of Chicago’s communities. We hope that this analysis will equip stakeholders to make well-informed decisions about the ongoing use of ShotSpotter technology.”
See the report at: bit.ly/CPDShotSpotter.