Chicago ShotSpotter: Costs, Lawsuits, and Shutdown Fallout

Chicago ended its ShotSpotter contract on September 23, 2024, making it the largest American city to drop the gunshot detection technology after six years and roughly $49 million in spending. Mayor Brandon Johnson pulled the plug citing studies that found the system rarely turned up evidence of gun crime, sent officers on tens of thousands of dead-end runs, and concentrated surveillance in Black and Latino neighborhoods. The legal and political fallout has continued into 2026, and the city still has no replacement in place.

What ShotSpotter Did in Chicago

ShotSpotter, made by a company now called SoundThinking, used outdoor microphones mounted on buildings and poles to detect the acoustic signature of gunfire. When sensors picked up a sound classified as a gunshot, the alert went through SoundThinking’s review center, where staff confirmed or filtered it before passing coordinates to Chicago’s Strategic Decision Support Centers. Officers were then dispatched, often before any 911 call. Chicago Police Department protocol treated every alert as an in-progress firearm crime requiring immediate response.¹

Chicago signed a three-year, $33 million contract with the company on August 20, 2018, covering roughly 100 square miles across 12 police districts on the South and West sides.² The deal was extended multiple times, first through August 2023, then February 2024, and finally to late September 2024. Cumulative spending reached about $49 million.³ Some City Council estimates put the total closer to $53 million.⁴

What the Data Showed

Independent reviews challenged the system’s core promise almost from the start.

The Inspector General’s Report

In August 2021 the Chicago Office of Inspector General published a review of 50,176 confirmed ShotSpotter alerts dispatched to police between January 2020 and May 2021. Just 9.1% turned up evidence of a gun-related crime. Only 2.1% were linked to a documented investigatory stop. The OIG concluded that the data “does not support a conclusion that ShotSpotter is an effective tool in developing evidence of gun-related crime.”² Deputy Inspector General Deborah Witzburg said the city, if it kept sending officers into potentially dangerous situations based on these alerts, “should be able to demonstrate the benefit of its use in combatting violent crime. The data we analyzed plainly doesn’t do that.”⁵

Dead-End Deployments

A MacArthur Justice Center analysis of data from July 2019 through April 2021 counted more than 40,000 “dead-end” police deployments over 21 months. On an average day, officers were sent on more than 61 runs that produced no evidence of any crime at all.⁶

Cost Per Arrest

The Cook County State’s Attorney’s Office found the system cost Chicago $217,368 for every person arrested in a ShotSpotter-related shooting incident, with only 1% of shooting incidents resulting in such an arrest. The office called ShotSpotter “an expensive tool that provides minimal return on investment to the prosecution of gun violence.”⁷

Academic Studies

A National Institute of Justice study published in January 2024 evaluated ShotSpotter in Chicago and Kansas City. In Chicago, officers did respond more often and got closer to incident locations when dispatched by ShotSpotter than by 911. Firearms were 45% more likely to be recovered from fatal shooting scenes in coverage areas. But those procedural gains “did not translate to any meaningful improvements to crime control outcomes,” with no statistically significant effect on evidence collection, case clearance, or overall crime reduction.⁸ A 2021 longitudinal study in the Journal of Urban Health, drawing on 68 large counties from 1999 to 2016, found “no significant impact on firearm-related homicides or arrest outcomes.”⁹

A Type Investigations review covering January 2023 through August 2024 also found the system missed more than 20% of shootings within its coverage area, never met the 90% detection rate required by contract, and produced no alert for 41% of fatal and nonfatal shootings in the coverage zone.¹⁰

Racial Equity and Civil Rights Concerns

ShotSpotter was deployed exclusively in police districts with the highest concentrations of Black and Latino residents.⁶ Critics argued the concentrated surveillance produced inflated crime statistics for those neighborhoods, which were then used to justify more police presence there.¹¹

The OIG report also found the technology changed how officers interacted with residents. Some officers cited the general frequency of alerts in an area as justification for stopping and frisking people, based on a neighborhood-wide perception of danger rather than a specific alert.¹ The MacArthur Justice Center called this a “powderkeg situation,” arguing that officers arriving already primed to expect an armed suspect were more likely to escalate encounters with anyone nearby.⁶

In September 2023, the Electronic Privacy Information Center petitioned the U.S. Department of Justice to investigate whether federally funded ShotSpotter deployments violated Title VI of the Civil Rights Act.¹² The DOJ has not publicly responded or launched an investigation as of 2026.¹³

Adam Toledo

Officers responding to a ShotSpotter alert detecting eight gunshots in Little Village around 3 a.m. on March 29, 2021, fatally shot 13-year-old Adam Toledo. Officer Eric Stillman fired in what former Cook County State’s Attorney Kim Foxx concluded was a reasonable belief he was in danger, declining to file criminal charges. The Civilian Office of Police Accountability later recommended Stillman’s termination, finding he used excessive force. Stillman has not returned to active duty.¹⁴ Toledo’s killing became a focal point in the political debate that eventually ended the program.

Michael Williams

Michael Williams, a 65-year-old Chicagoan, was charged with murder in 2020 after a ShotSpotter alert was used to build a case against him. Williams had been driving his neighbor, 25-year-old Safarian Herring, when Herring was fatally shot. Police theorized the shot was fired inside the vehicle, relying in part on ShotSpotter data. Williams spent nearly a year in jail before a Cook County judge dismissed the charges in July 2021 for insufficient evidence.¹⁵ SoundThinking later stated it had contacted prosecutors to explain that its technology is not designed to detect gunfire within an enclosed vehicle and that the acoustic evidence did not support the theory.¹⁶ Williams sued the city in federal court in July 2022, and in early 2026 Chicago agreed to pay him $500,000 to settle through an offer of judgment that did not include an admission of liability.

How the Contract Ended

Brandon Johnson ran for mayor in 2023 on an explicit promise to remove ShotSpotter. On February 13, 2024, he announced the contract would not be renewed, calling the system “unreliable and overly susceptible to human error.”³ The system went dark at 12:01 a.m. on September 23, 2024, followed by a 60-day period during which sensors were removed from 12 South and West side neighborhoods.¹⁷

The City Council fought Johnson hard. In May 2024, aldermen voted 34-14 to demand a council vote before ShotSpotter could be removed from any ward.¹⁸ Johnson dismissed the vote, saying the council lacked executive authority over city contracts. In September 2024, days before the contract expired, aldermen voted 33-14 to pass an ordinance authorizing the police superintendent to independently extend or sign a new contract without mayoral approval. Johnson vetoed it, and the override vote fell one short.¹⁷ His administration argued the ordinance violated the separation of powers.¹⁹

Supporters, including Alderman David Moore, argued the system helped officers reach gunshot victims when no 911 call was placed, citing data that 91 lives were saved via alerts between January 2023 and July 2024.⁴ Opponents, including Alderman Jessie Fuentes, countered that “there was no evidence ShotSpotter makes Chicago safer.”¹⁸

Lawsuits and Settlements

Beyond the Williams payment, the most significant case was Ortiz v. City of Chicago (No. 22-cv-3773), a class-action lawsuit filed by the MacArthur Justice Center on behalf of residents who alleged they were unlawfully stopped and frisked based solely on their proximity to ShotSpotter alerts. The complaint framed the stops as Fourth Amendment violations and alleged that the racially concentrated sensor deployment violated the Illinois Civil Rights Act.²⁰

In August 2025, the city settled for $90,000 and formally agreed that a ShotSpotter alert does not give police justification to stop or pat down someone who happens to be near the alert’s location. The settlement added a forward-looking provision: if Chicago ever contracts with ShotSpotter again, the city must adopt a police directive acknowledging that an alert alone does not constitute reasonable suspicion.²¹²²

Separately, the Illinois Appellate Court held in People v. Merritt Jones (2023) that when police rely on a ShotSpotter alert to establish reasonable suspicion for a stop, defendants are entitled to discovery about the system’s reliability. The court ordered ShotSpotter to produce calibration logs, reclassification records, and analyst qualifications.²³

What Has Happened Since the Shutdown

The aftermath has been intensely contested, with both sides pointing to data.

An analysis by Rob Vargas of the University of Chicago Justice Project found that in the six months after deactivation, CPD response times to the most serious 911 calls improved by an average of four minutes across the 12 South and West side neighborhoods where sensors had operated. In the 10th Ward, six of eight police beats saw response times drop by an average of 8.5 minutes. During the nine months after removal, homicides in the former ShotSpotter neighborhoods fell more than 32% and violent crime dropped more than 11% compared with the prior nine months.²⁴ Citywide, Chicago recorded 416 homicides in 2025, a 29% decline from 2024, and shooting incidents fell 35%.²⁵

Critics challenged the Vargas study. It excluded all 911 calls involving reports of gunfire, meaning it did not measure response times for the exact category of emergency ShotSpotter was designed to address. The “before” and “after” periods also compared different seasons, which typically have different call volumes and staffing. Vargas said his models accounted for monthly variation but declined to release the raw data, and the study was not peer-reviewed. SoundThinking CEO Ralph Clark pointed to five peer-reviewed studies suggesting gunshot detection improves police response times.²⁶ At a June 2026 Public Safety Committee hearing, Vargas himself testified that his study could not be used to draw causal conclusions, saying “a single before and after comparison cannot carry that weight.”²⁷

The Stalled Replacement

Nearly two years after decommissioning, Chicago still has no replacement in place. The city issued a request for proposals in February 2025 and received nine bids by an April 2025 deadline, including one from SoundThinking.²⁸ Chief Procurement Officer Sharia Roberts has said the city does not expect to award a contract until February 2027, noting that a procurement of this complexity typically takes at least two years. Alderman Brian Hopkins and other council members have pushed for the process to be completed within 90 days, calling the timeline “excessive” and “harmful.”²⁹ Johnson has said the previous system was “junk” and that the city is vetting bidders carefully to avoid repeating past mistakes.

Chicago is not alone. Several other cities dropped or declined to renew their ShotSpotter contracts during the same period, including Charlotte, San Antonio, San Diego, and Fall River, Massachusetts.³⁰ New York City kept its agreement, which SoundThinking described in early 2026 as “fully intact” with no proposed reductions.³¹

1
Chicago Office of Inspector General. Chicago Police Department’s Use of ShotSpotter Technology
2
Chicago Office of Inspector General. OIG Finds That ShotSpotter Alerts Rarely Lead to Evidence of a Gun-Related Crime
3
WTTW News. Mayor Brandon Johnson Cancels ShotSpotter Contract, Fulfilling Major Campaign Promise
4
ABC 7 Chicago. Chicago City Council Members Working to Prevent Mayor Brandon Johnson From Ending ShotSpotter Contract
5
WTTW News. ShotSpotter Alerts Rarely Lead to Evidence of Gun Crime, City Watchdog
6
MacArthur Justice Center. ShotSpotter Generated Over 40,000 Dead-End Police Deployments in Chicago in 21 Months
7
CBS News Chicago. ShotSpotter Report, Cook County State’s Attorney Kim Foxx
8
National Institute of Justice. The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago
9
National Library of Medicine. Impact of ShotSpotter Technology on Firearm Homicides and Arrests Among Large Metropolitan Counties
10
Type Investigations. ShotSpotter Missed Reported Shootings, Chicago Police
11
Vanderbilt Law. Failures of Predictive Policing: Chicago’s ShotSpotter Program
12
Wired. ShotSpotter DOJ Letter, EPIC
13
EPIC. EPIC Letter to Attorney General Garland Re ShotSpotter Title VI Compliance
14
WTTW News. Adam Toledo’s Family Sues City Again Over 13-Year-Old’s Death
15
WTTW News. Chicago Man Was Charged With Murder Based on ShotSpotter Alert; Now City Will Pay Him $500K
16
SoundThinking. Statement From SoundThinking on City of Chicago Michael Williams Settlement
17
ABC 7 Chicago. Chicago ShotSpotter Contract Ends Sunday
18
WTTW News. City Council Votes 34-14 to Endorse Effort to Overturn Mayor’s Decision to Scrap ShotSpotter
19
Courthouse News Service. Chicago City Councilors Vote to Go Around Mayor in Effort to Keep ShotSpotter Surveillance Tech
20
MacArthur Justice Center. Chicago Agrees to Settle Lawsuit Challenging Its Use of ShotSpotter
21
Chicago Sun-Times. Chicago Police Crime ShotSpotter SoundThinking CPD Mayor Brandon Johnson
22
MacArthur Justice Center. Williams v. City of Chicago
23
FindLaw. People of the State of Illinois v. Merritt Jones
24
WTTW News. CPD Officers Responded Faster to 911 Calls on South, West Sides After ShotSpotter Was Removed
25
Chicago Police Department. 2025 in Review
26
CWB Chicago. Mayor Says Study Proves Police Respond Faster Without ShotSpotter; The Study Excluded Gunfire Calls
27
ABC 7 Chicago. Search for Replacement Chicago Shootings Detection Technology Stalls Amid Delays
28
Block Club Chicago. More Than a Year After Mayor Promised ShotSpotter Replacement, Alders Demand What’s Taking So Long
29
CBS News Chicago. ShotSpotter Replacement Public Safety Committee Meeting
30
ACLU of Massachusetts. ACLU of Massachusetts Calls on Somerville to Cancel ShotSpotter Contract
31
Motley Fool. SoundThinking Q4 2025 Earnings Transcript