CHICAGO · SHOTSPOTTER

50,176 dispatched alerts; documented gun-crime evidence appeared in a small minority of responses.

9.1% of dispositions documented gun-related criminal evidence

WHERE

Chicago · Cook County · IL

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Chicago OIG analyzed ShotSpotter alerts from January 2020 through May 2021. It identified 50,176 alerts confirmed by ShotSpotter as probable gunfire and dispatched to CPD. Of the 41,830 responses with a recorded disposition, 4,556—9.1%—documented evidence of a gun-related criminal offense. Only 1,056 of all 50,176 dispatched alerts, or 2.1%, shared an event number with a documented investigatory stop.

OIG also found evidence that the volume of ShotSpotter alerts in an area could affect how some officers perceived and interacted with people there. In other words, an alert system could influence policing even when a particular alert did not produce a gun case.

Why it matters: A system can create consequences without falsely naming a specific person. Repeated machine-generated suspicion can redirect police attention toward a place and the people in it.

Source: Chicago OIG Public Safety Annual Report 2021

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