ShotSpotter's Success in Chicago
As of this week, the city of Chicago will no longer use ShotSpotter—the controversial gunshot alert technology that detects audio of gunshots throughout a city and automatically informs police.
The service was targeted by incoming mayor Brandon Johnson who ran for office swearing he would eliminate it from the budget.
While Chicago aldermen and police overwhelmingly supported the use of ShotSpotter for its ability to alert police earlier and more often than 911, Johnson and others criticized its high price tag—on the order of $10 million a year—calling it ineffective and encouraging over-policing.
A 2021 Chicago Office of the Inspector General (OIG) report on the technology repeated an accusation from the MacArthur Justice Center—a pro-civil rights group—that few ShotSpotter alerts lead to arrests, undercutting the program’s usefulness.
Only 2.1 percent of police dispatches from ShotSpotter led to investigatory stops. Of those stops, the majority—70.5 percent—were for “miscellaneous” events, and just 10.9 percent were likely related to gun violence or gun possession. It also states “a large percentage of ShotSpotter alerts cannot be connected to any verifiable shooting incident.”
But based on the numbers published in the report, ShotSpotter alerts highly correlate with gun-related arrests (Pearson: .882). While alerts far outnumber gun related arrests, more ShotSpotter alerts meant more gun-related arrests.
Somehow ShotSpotter is alerting police to lots of gunfire and police are making more gun-related arrests when they happen, but according to the OIG report the two are not connected—potentially because the report didn’t connect enough ShotSpotter alerts to the relevant police actions.
While the report extended considerable effort to connect ShotSpotter alerts with police actions, it also notes that not all ShotSpotter-related events were connected:
These cases suggest that the exercise of matching individual ShotSpotter alerts to subsequent associated investigatory stops alone may underrepresent the extent to which the introduction of ShotSpotter technology in Chicago has changed the way CPD members perceive and interact with individuals present in areas where ShotSpotter alerts are frequent. At least some officers, at least some of the time, are relying on ShotSpotter results in the aggregate to provide an additional rationale to initiate stop or to conduct a pat down once a stop has been initiated.
More Guns Recovered Following Its Implementation
The introduction of ShotSpotter has also seen a significant increase in gun recoveries. What was 8,000 to 10,000 a year based on Chicago Police Department (CPD) annual reports steadily increased since ShotSpotter’s introduction in 2018 to over 12,000 a year.
