ERIC WESTERVELT, HOST:
To combat gun violence, dozens of U.S. cities use a gunfire detection tool called ShotSpotter. Microphones dotted around town capture the sound of gunshots, which can help police pinpoint where they came from and get there to investigate. But the technology is controversial, and some cities have rejected it. Member station WBEZ's Chip Mitchell reports that Chicago let its ShotSpotter contract expire, and the city is now looking for something new.
CHIP MITCHELL, BYLINE: Chicago has long struggled with gun violence. Seven years ago, city officials had high hopes for technology they'd been trying out in the two police districts with the most shootings.
EDDIE JOHNSON: It is a good tool in terms of getting us to that scene a lot quicker.
MITCHELL: Eddie Johnson. He was the police superintendent. He said the technology was ShotSpotter.
JOHNSON: What this does is pinpoint where that shot came from, and we respond quicker because we don't have to wait for the 911 call. So typically now it'll be real-time deployments.
MITCHELL: Johnson said the goals were arrests and violent crime reduction. Within a few years, more than 2,000 audio sensors covered about half the city, and Chicago was paying the company, now called SoundThinking, roughly $10 million a year. SoundThinking says more than 170 jurisdictions use its gunfire detection system. While cops and others find it useful, some researchers are questioning its effectiveness. Chicago Inspector General Deborah Witzburg told the city council about findings by her office.
DEBORAH WITZBURG: We looked at about 50,000 ShotSpotter alerts, and we found that in only about 9% of those did CPD make a record of collecting evidence related to a gun crime.
MITCHELL: Other research found problems, too. Economist Michael Topper of the Social Science Research Council says the technology actually delays help for 911 callers in Chicago.
MICHAEL TOPPER: Police officers are responding about two minutes slower to get on scene. This slower response time is actually going to result in fewer arrests occurring at these 911 calls.
MITCHELL: Still, others complain that, because Chicago's ShotSpotter sensors were mostly in Black and Latino neighborhoods, the system contributed to overpolicing them. That caught Brandon Johnson's ear before he won last year's mayoral election. During his campaign, he promised to pull the plug on the gunshot technology. Other cities, including Atlanta and New Orleans, rejected ShotSpotter, too. But in Chicago, there was a big fight about the decision. Some city council members, researchers and the company itself argued ShotSpotter, even if it hadn't reduced crime, had saved lives of gunshot victims. Alderman Anthony Beale recalled a cop who was gunned down last year.
ANTHONY BEALE: Areanah Preston. If it had not been for ShotSpotter, she would still be laying in that front yard. We need this tool in this city.
MITCHELL: But the mayor didn't change his mind. He let the contract expire. Now Chicago's looking for different law enforcement technology. Besides gunshot detection, companies are offering vehicle license plate readers. They would enable the police to generate a list of cars near a gunfire scene. Texas A&M University law professor Hannah Bloch-Wehba says that's controversial, too.
HANNAH BLOCH-WEHBA: Civil libertarians are not thrilled about pervasive location tracking, but no court has said that it's unconstitutional.
MITCHELL: She says Chicago and other cities have to decide whether their police officers should spend more time responding to gunshot alerts or doing things like getting to know more people in the communities where they work, beefing up shooting investigations or just answering 911 calls for NPR news. I'm Chip Mitchell in Chicago.
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