A ShotSpotter device on a light pole surveils the intersection of 87th and Carpenter (photographed in January 2024). Credit: Jim Daley

Shotspotter, an acoustic gunshot-detection technology company, has built a network of thousands of sensors across twelve of Chicago’s twenty-two police districts. The devices detect loud noises that a computer algorithm and human analysts review to determine if they’re gunshots, and dispatch police to scenes of shootings. The technology is controversial: studies have raised questions about its efficacy and how it impacts police responses, and activists have called on the city to cancel its contract with ShotSpotter for years.

This months-long investigation was published shortly before Mayor Brandon Johnson’s February 13 announcement that he would fulfill his campaign promise to not renew ShotSpotter’s contract, which expired a few days later. The investigation combined internal company emails, documents obtained from the police department and Mayor’s Office via public-records requests, interviews, on-the-ground reporting and analysis of public data.

We found that CPD reported hundreds of missed shootings to ShotSpotter in 2023; that a public safety director complained to the company about a fifty-five-round shooting in 2022 because of broken sensors; executives’ internal discussions about staffing issues that impacted their ability to repair sensors in Chicago; that the company was warned about electrical code violations on its installations; and that executives lobbied Johnson’s administration to keep the contract. Our reporting also found ShotSpotter coverage areas in districts the city hasn’t acknowledged them being in.

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In December 2022, two men were wounded in a hail of bullets as they waited for food in a gyro shop in Back of the Yards. The next day, a Public Safety Administration director complained to a ShotSpotter executive that the company’s senors failed to detect the shooting. Data we obtained from CPD shows the department reported hundreds of missed shootings to ShotSpotter in 2023.

Internal emails show ShotSpotter executives blamed the miss on three downed sensors in the vicinity. The executives didn’t know when the company would be able to repair the downed sensors—and said they could not admit that to public safety officials. Other emails show ShotSpotter managers were repeatedly warned that sensor installations were violating Chicago’s electrical code.


In 2019, the French billboard company JCDecaux asked ShotSpotter to monitor the areas around several electronic billboards it claimed had been shot at on the far Northwest Side. With the city’s blessing, ShotSpotter obliged. The company established three small coverage areas around the billboards, which are in neighborhoods that have some of the lowest levels of gun violence in the city. The coverage area is provided “at no cost to anyone,” according to a spokesperson—but CPD still gets about twenty to thirty alerts from these monitors per year, and has to respond to them.


After Johnson was elected in April 2023, ShotSpotter CEO Ralph Clark issued a public statement congratulating the mayor-elect. That same day, Clark sent an email to employees that blamed the company’s share price drop on Johnson’s victory and said executives planned to lobby support for renewing the contract. Emails obtained from the Mayor’s Office reveal how that lobbying effort played out—and show executives met with mayoral advisor Jason Lee days before the 2024 budget vote in City Council.


In November, the day before the City Council voted on Mayor Johnson’s 2024 budget, ShotSpotter’s CEO told investors in an earnings call that there was a line item in the budget for acoustic gunshot surveillance technology. Both the CEO and a spokesperson for the mayor denied anyone had given the company any indication the contract would be extended.

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