Police Are Using Gunshot Detection Tech To Justify Stop-and-Frisks

In Chicago, a government watchdog says Shotspotter alerts have only led to evidence of gun crime in 9 percent of cases.
Chicago Tribune / Getty Images

Police watchdogs in Chicago have issued a report about the city’s use of ShotSpotter’s acoustic gunshot detection system, finding that only 9 percent of ShotSpotter alerts led to evidence of gun crime.

“A large percentage of ShotSpotter alerts cannot be connected to any verifiable shooting incident,” the city's Office of Inspector General (OIG) wrote.


Despite that low rate of return, the OIG found that Chicago Police Department officers are using the technology to justify stopping and searching city residents in some cases.

“Some officers during the reporting period identified the fact of being in an area known to have frequent ShotSpotter alerts as an element of the reasonable suspicion required to justify the stop,” according to the report, which covered January 2020 through May 2021. “Other officers reported conducting ‘protective pat downs’ following a stop because they knew themselves to be in areas where ShotSpotter alerts were frequent.”;The OIG found that Chicago police used Shotspotter to justify stops in 10 of 72 cases it randomly selected for a more detailed review. Only one of these cases led to an arrest, according to the report. The report states that in these cases, “reporting officers referred to the aggregate results of the ShotSpotter system as informing their decision to initiate a stop or their course of action during the stop, even when they were not responding to a specific ShotSpotter alert.”

The OIG analyzed 50,176 Shotspotter alerts in the city's database and found that 4,556 reports—or 9.1 percent—indicated that police found evidence of a gun-related crime in connection to the alert. An additional 16.6 percent of reports had no disposition code that allowed the report authors to draw a conclusion.


During the review period, Chicago police stopped 1,740 people in relation to a ShotSpotter alert but “fewer than 2 in 10 investigatory stops following ShotSpotter alerts resulted in the recovery of a gun,” according to the report. In total, the department recovered 152 guns.

The report comes after Chicago media reported that the city quietly renewed its three-year, $33 million contract with ShotSpotter in December. The contract wasn’t set to expire until August 19, and some Chicago residents have taken to the streets in recent weeks to demand that city officials end the contract—not knowing it had already been extended for another two years. Mayor Lori Lightfoot's office did not respond to a request for comment.

“ShotSpotter has detected hundreds of shootings that would have otherwise gone unreported,” Chicago Police Department spokesperson Thomas Ahern wrote in an email to Motherboard.

“It is important to point out that the Chicago Police Department continually describes ShotSpotter as an important part of their operations,” ShotSpotter wrote in a statement to Motherboard. “The OIG report does not negatively reflect on ShotSpotter’s accuracy which has been independently audited at 97 percent based on feedback from more than 120 customers. Nor does the OIG propose that ShotSpotter alerts are not indicative of actual gunfire whether or not physical evidence is recovered.”


The “independent” report ShotSpotter referenced came from a company called Edgeworth Analytics, and was paid for by ShotSpotter. 

ShotSpotter’s sensors in Chicago and other cities are installed overwhelmingly in Black and brown neighborhoods, according to data obtained by Motherboard using public records requests. 

In general, police department customers determine coverage areas with assistance from ShotSpotter by analyzing historical gunfire and homicide data to assess areas most in need of gunshot detection,” Sam Klepper, senior vice president for marketing and product strategy at ShotSpotter, wrote to Motherboard for an earlier article about ShotSpotter microphone placement. 

“We believe all residents that live in communities experiencing persistent gunfire deserve a rapid police response that gunshot detection enables, regardless of race or geographic location,” Klepper added. “While gun violence can unfortunately happen anywhere at any time, cities lack sufficient funds to cover an entire city with gunshot detection technology, so they most commonly deploy sensors in neighborhoods with the highest levels of gun violence to make the greatest impact."

The OIG report prompted further calls from local activists for city officials to cancel the ShotSpotter contract.

“Despite consistent demands from communities impacted by gun violence that the city of Chicago invest in proven public safety programs, our elected officials continue to choose to spend our tax dollars on surveillance technologies that only serve to further criminalize Black and brown communities,” Alyx Goodwin, an organizer with the #StopShotSpotter Coalition in Chicago, wrote in a statement to Motherboard. “We once again call on the city to cancel its existing ShotSpotter contract.”