Politics
CPD Officers Responded Faster to 911 Calls on South, West Sides After ShotSpotter Was Removed: UChicago Analysis
A screenshot of a ShotSpotter alert. (WTTW News)
Chicago police responded four minutes faster to the most serious 911 calls for help in the six months after Mayor Brandon Johnson scrapped the city’s controversial ShotSpotter gunshot detection system in 12 South and West side neighborhoods, an analysis of Chicago crime data in those neighborhoods shows.
Using data obtained through Freedom of Information Act requests as well as data published by the city, Rob Vargas, a sociology professor at the University of Chicago who leads the UChicago Justice Project, found there is no evidence that Johnson’s decision to turn off the microphones that sent an alert to police officers every time the system picked up suspected gunfire slowed police response times or drove up violent crime, as many warned.
Response times dropped across the city during the six months after Johnson scrapped the system in September 2024 over the vehement objections of a majority of the Chicago City Council, as compared with the six months before it was shuttered, according to the analysis.
But response times dropped faster in police beats where the gunshot detection system had been operational, according to the analysis, which examined CPD response times to 911 calls given the highest priority that did not involve reports of gunshots, according to the analysis.
CPD data did not always distinguish between ShotSpotter-initiated alerts to the Office of Emergency Management and Communications and those reported to 911 making it impossible to compare gunshot response times, Vargas said.
“It is clear that ShotSpotter wasted officers’ time by sending them on wild goose chases,” Vargas told WTTW News.
Police response times dropped in beats that had ShotSpotter even though many of those neighborhoods are among the city’s most violent, especially during the summer months, according to the analysis.
In the neighborhoods that had ShotSpotter, homicides dropped more than 32% during the nine months after the system was decommissioned, as compared with the nine months before it was turned off, according to the analysis. Violent crime dropped more than 11% during the same period in those neighborhoods, according to the analysis.
The analysis is the second time Vargas has examined the result of Johnson’s decision to turn off the sensors despite intense warnings that police officers would be unable to stop a wave of gun violence without its help.
Vargas said his first analysis, which showed a steep drop in the number of shootings and homicides in neighborhoods where the gunshot detection system was in place, prompted by warnings of “doom and gloom.”
Vargas said he decided to examine the impact of ShotSpotter’s removal on police response times as members of the Chicago City Council ratcheted up the pressure on Johnson to replace the system, insisting that the city must act quickly to give police officers a critical tool.
But the city’s own data shows that there is “zero evidence” that ShotSpotter — or any gunshot detection tool — would have a positive impact on crime and violence in Chicago, Vargas said.
“The data is missing in this debate,” Vargas said. “There should have been a collective breath of relief that this decommissioning didn’t lead to catastrophe, but the data hasn’t changed the debate.”
The City Council’s Public Safety Committee is set to again press city officials on their efforts to award new contract for a gunshot detection system at a June 3 meeting, after a meeting two weeks ago failed to shed any light on the nearly 19-month effort to negotiate a new gunshot detection contract.
“This data should inform that evaluation,” Vargas said. “Officers deserve to have technology that works.”
The drop in police response times was especially significant in the 10th Ward, which covers the city’s Southeast Side, according to the analysis.
Across six of the ward’s eight beats, all of which had ShotSpotter sensors, response times dropped an average of 8.5 minutes, according to the analysis, while response times were unchanged in another beat and rose by less than a minute in another.
But Ald. Peter Chico (10th Ward), a former Chicago police officer, told WTTW News that data would not change his firm belief that residents of his ward would be safer if a gunshot detection system covered the ward.
“My community wants this tool,” Chico said, adding that he gets emails everyday asking when the system would be back up and running. “What about when there are no calls?”
Chico and other supporters of the gunshot detection system, including Chicago Police Supt. Larry Snelling, contend it helped officers save lives when shootings were not reported to emergency services.
ShotSpotter was never used to dispatch paramedics.
The City Council twice rebuked Johnson over ShotSpotter and demanded that he reverse his decision to scrap the system, which he has said leads to the overpolicing of neighborhoods home to a majority of Black and Latino Chicagoans and derided as no better than a “walkie-talkie on a stick.”
Johnson has repeatedly said there is “clear evidence (ShotSpotter) is unreliable and overly susceptible to human error.” He blamed the system for the death of 13-year-old Adam Toledo, who was shot and killed by a Chicago police officer responding to an alert from the system in March 2021.
Johnson said there was no evidence that ShotSpotter lived up to promises that it would reduce gun violence.
Under fire, Johnson’s administration agreed to consider proposals from firms to use technology to “ensure quick response by law enforcement authorities in emergency situations.”
City officials required gunshot detection systems to cover the entire city of Chicago and be able to report “incidents” to police with positional data within 60 seconds, with 95% accuracy, to help the city “improve detection of violent crime, expedite response times, improve the likelihood of obtaining forensic evidence and speed up medical response and first aid for victims.”
The city’s 2026 budget includes $5 million for “software maintenance and licensing” as proposed by the mayor that could be used to fund another contract with SoundThinking or another firm to provide a gunshot detection system.
That is less than the $9 million the city set aside in its 2025 budget for a ShotSpotter replacement, records show. It is unclear whether a gunshot detection system exists that meets the city’s specifications.
Johnson said Feb. 18 he would not ink a new contract until officials could “find something that works” while continuing to focus on what he said has proven to reduce crime in Chicago, like reopening mental health clinics, building affordable homes, improving public education and helping detectives solve crimes and get illegal guns off the street.
“The things that are working, we’re going to double down those efforts,” Johnson said. “And then, of course, we’ll still have conversations about, you know, ways in which we can solidify their work along the edges.”
Any decision to re-implement a gunshot detection system in Chicago would come after the city agreed to pay $90,000 to resolve a lawsuit filed by the MacArthur Justice Center, a nonprofit civil rights organization in Chicago.
That suit alleged the city used ShotSpotter alerts as a pretext to stop and search Chicagoans near the alert without other reasonable suspicion or probable cause, records show.
Chicago taxpayers will pay $500,000 to resolve a separate lawsuit filed by a man who was charged with a murder in 2020 based on an alert from ShotSpotter, according to court records.
WTTW News coverage of policing and police reform is supported by The Joyce Foundation.
Contact Heather Cherone: @HeatherCherone | (773) 569-1863 | [email protected]
