The city of Chicago will not renew its contract to use the controversial gunshot detection system ShotSpotter and plans to decommission the technology later this year, Mayor Brandon Johnson’s office announced Tuesday.

The system — which uses acoustic sensors and machine algorithms to detect and locate gunfire incidents — has been widely criticized by watchdog and public safety groups for its ineffectiveness and racial bias. Since 2018, Chicago has spent $49 million on ShotSpotter.

The city's contract with SoundThinking, a public safety technology company that says its ShotSpotter technology is used in more than 150 cities and several U.S. campuses, expires on Friday. According to Johnson's office, the city will stop using the technology on Sept. 22.

"Moving forward, the City of Chicago will deploy its resources on the most effective strategies and tactics proven to accelerate the current downward trend in violent crime," the city said in a statement. "Doing this work, in consultation with community, violence prevention organizations, and law enforcement, provides a pathway to a better, stronger, safer Chicago for all."

Tuesday's announcement also stands by Johnson's mayoral campaign promise to get rid of the gunshot detection system. Community members and public safety groups have argued that investment in the technology is a waste of resources, saying city officials should work on other crime and gun violence prevention methods.

The Stop ShotSpotter Coalition and United Working Families celebrated Johnson's decision but noted the technology has already harmed Chicago residents and that the city should have stopped using it sooner.

"Victims, survivors, their families, and the communities with the highest rates of gun violence deserve more tangible support, resources and solutions that have been forgone due to investments in policing and technology that do not prevent or reduce violence," the coalition said in a Tuesday statement. "This decision is an unprecedented one which wasn't possible before Mayor Johnson, but we will continue to organize until all of ShotSpotter's microphones are removed from Chicago."

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Gunshot detectors in U.S. cities

High-tech gunshot detection systems have been used by law enforcement agencies in big cities for years. Police leaders have advocated for the use of these systems and their expansion, arguing that the technology helps save lives and reduces crime rates.

"Technology is where policing is going as a whole. If we’re not utilizing technology, then we fall behind in crime fighting," Chicago Police Superintendent Larry Snelling told The Associated Press last October. "There are always going to be issues. Nothing is 100% and nothing’s going to be perfect."

Gunshot detection systems use a network of microphones that are installed around the city to identify gunshots, including pinpointing their location and alerting police, according to the American Civil Liberties Union. In 2015, the ACLU reported that ShotSpotter's "sensors constantly record audio, and monitor that audio for explosion-like noises like a gunshot."

The ACLU and community public safety groups have questioned the technology, citing inaccuracy, privacy concerns, and biased policing.

Critics have argued that the technology sends law enforcement officers to predominantly Black and Latino neighborhoods for often unnecessary and hostile encounters. The MacArthur Justice Center found that about 89% of ShotSpotter reports didn’t result in police reporting an incident involving a gun, and 86% led to no crime at all, according to a 2021 report that reviewed Chicago data from July 2019 to April 2021.

Some cities, including Charlotte, North Carolina, and San Antonio, Texas, ended their ShotSpotter contracts because the technology mistakenly identified fireworks or motorcycle sounds as gunshots.

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ShotSpotter in Chicago

During Johnson's mayoral campaign, he promised to end the ShotSpotter contract and said the city spends $9 million a year on the system "despite clear evidence it is unreliable and overly susceptible to human error."

Johnson and public safety groups have cited the case of 13-year-old Adam Toledo, who was shot and killed by a Chicago Police Department officer in 2021 after police received a ShotSpotter alert. In 2022, an Associated Press investigation detailed how authorities used ShotSpotter data to charge a Chicago grandfather with murder before a judge dismissed the case due to insufficient evidence.

The system was also recently criticized by officials for being ineffective and overly costly. In a leaked report from the Cook County State's Attorney's Office last week, the office found the technology had no significant impact on shooting incidents and prosecuting gun violence cases.

Johnson's office says that the Chicago Police Department will "revamp operations" ahead of the system's decommissioning in September, including implementing new training and further developing response models to gun violence.

"During the interim period, law enforcement and other community safety stakeholders will assess tools and programs that effectively increase both safety and trust and issue recommendations to that effect," the city said.

Contributing: The Associated Press