Study Raises Questions over Chicago Police's Use of ShotSpotter

A city inspector general analysis of the Chicago Police Department’s multimillion-dollar gunshot-detection system has found that it rarely results in officers documenting gun violence.

The study also found that in some cases officers are using ShotSpotter as part of their justification for street stops.

Deputy Inspector General Deborah Witzburg said the findings should raise serious questions for the city about continuing to invest in the ShotSpotter technology, which is currently used in 12 districts, primarily on the South and West sides, and relies on sensors to detect when a gun is fired and then directs officers to respond.

The report lands as the reliance on the ShotSpotter technology by Chicago police to fight gun violence faces increased criticism, both by community members and the Cook County public defender’s office, which has filed motions to challenge the use of ShotSpotter evidence in court against defendants.

In a statement, the Chicago Police Department stood by the use of ShotSpotter, saying detecting where gun violence occurs quickly to direct responses is “crucial” and that it is useful to officers in a few different ways.

“Instead of relying on the historically low rate of 9-1-1 calls, law enforcement can respond more quickly to locate and aid victims, identify witnesses, and collect forensic evidence,” the statement said.

The report included an analysis of 50,000 ShotSpotter alerts between January 2020 and May 2021. Of the 42,000 that documented a police response, only 9% included a gun-related criminal offense. The findings are similar to a study conducted by the MacArthur Justice Center earlier this summer.

Witzburg noted, however, that the analysis did not conclude that failure to document a gunshot meant there was not gunfire. But she said the lack of evidence to show that the alerts translate to documented police action on gun violence raises questions about why the city is investing in the program.

“In situations where there is no gun-crime-related disposition ... that certainly does not necessarily mean there wasn’t a gunshot fired,” she said. “Even if the technology is correctly identifying the sound of a gunshot, if the identification of that sound is not helping the police to identify and control gun crime, then it doesn’t have any demonstrable operational value.”

The analysis also found that among the 50,000 alerts, a total of 1,056, or 2%, were linked to an investigatory stop, suggesting the stop happened as a “direct result” of an alert from the system. There were an additional 1,300 documented stops in which a keyword search of the report narratives suggested that officers’ general knowledge of ShotSpotter alerts in the area had contributed to the reason for the stop.

The report concluded that the technology had “changed the way some CPD members perceive and interact with individuals present in areas where ShotSpotter alerts are frequent.”

Witzburg added that this means officers are taking such police action when there are “concerns about the value of technology in the first place.”

In a written statement, the Cook County public defender’s office said the findings in the report confirm claims the office has made in court.

“The huge majority of ShotSpotter alerts are false alerts involving no real criminal activity,” Brendan Max, chief of the forensic science division for the office, wrote in the statement. “The Chicago Police Department should discontinue their unlawful practice of using ShotSpotter alerts as the justification (to) stop and frisk Chicagoans who just happen to be in the area of ShotSpotter alerts.”

Max also wrote that, in light of the recent revelations about ShotSpotter evidence, judges “must take a close look at whether this evidence is reliable enough to be used in criminal trials.”

The city had been under a three-year, $33 million contract with ShotSpotter through August 2021. In December 2020, the contract was extended through August 2023, according to the IG report.

In the department’s statement, officials said ShotSpotter was “among a host of tools used by the Chicago Police Department to keep the public safe and ultimately save lives.”

“In order to reduce gun violence, knowing where it occurs is crucial,” an emailed statement said. “ShotSpotter has detected hundreds of shootings that would have otherwise gone unreported.”

The statement further describes how the “real-time alerts” enable patrol officers to “arrive at a precise location of a shooting event quickly.”

Witzberg also noted that the department needs to evaluate these benefits and then weigh them against other issues, including the financial cost, community concerns and also the safety of officers who respond to the alerts.

“What is called for here is a cost-benefit analysis,” she said.

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