Are Shot Detection Microphones Worth The Money?


WBUY AROUND one of Chicago’s poorest neighborhoods and look at the street lights. You will see that many of them have protrusions protruding several feet above the light. These are microphones operated by ShotSpotter, a company headquartered in California. They are spread over much of Chicago and pick up the sounds of gunfire. The algorithms detect the sounds, which are then verified by humans listening from a control center in Washington, CC. Triangulating the sounds of multiple microphones reveals where the guns were fired. Police are alerted and rush to the scene, faster than if they were to wait for a 911 call, especially a call that may not come.

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In any case, that’s the idea. Over the past 25 years, ShotSpotter’s technology has spread across America. It is now used in over 100 cities. Chicago is its largest market, with the police department paying around $ 11 million a year for the service, accounting for nearly a fifth of the company’s revenue. In the past year, Chicago has claimed 795 homicide victims, almost all of them from shootings.

The use of sensors is increasingly controversial, in Chicago and elsewhere. In August, the Chicago Inspector General’s office (BIG), a city watchdog, produced a report questioning the usefulness of the technology. On November 12, the city council’s public security committee held a special hearing to question the police and the company about the concerns. On November 3, Baltimore decided to renew his contract, but narrowly: Mayor Brandon Scott said he was the “biggest skeptic” and that assessments would continue. Other cities, such as Charlotte, North Carolina, have terminated their contracts. Is the technology worth it?

According to BIG, out of just over 50,000 alerts generated by the system between January 2020 and May 2021, only around 2% resulted in the police arresting someone. Only 0.4% of alerts resulted in arrests and even fewer in the recovery of weapons. A separate study from the MacArthur Justice Center, a civil rights law firm affiliated with Northwestern University, found that in only 10% of system-generated cases, police could find evidence of a shooting, such as than used cartridge cases or bullet holes.

And yet, each alert is assimilated to an ongoing shooting, specifies Jonathan Manes, of the MacArthur center, which makes that several police officers rush on the scene. In Chicago, police respond to about 60 alerts per day. Those resources, along with the money spent on the system itself, could be used to investigate the crimes that have been reported, he says. Less than half of the murders in Chicago are solved.

“ShotSpotter technology does not deter crime or shootings,” says Ray Kelly of the Citizens Policing Project, a Baltimore group that calls for a closer relationship between police and citizens. “So what’s the advantage? Police reform activists in Chicago point to the trial of Michael Williams, a 65-year-old black man who was arrested last year for murder. The prosecution presented evidence from the ShotSpotter system to claim that he killed a young man in his car. The case turned out to be fragile and in July Williams was released. In another case, in March, an unarmed 13-year-old boy was shot dead by police responding to an alert.

Deborah Witzburg, who was assistant inspector general for public safety in Chicago until Nov. 12, points out that the city’s police department, which has a long history of allegations of abuse, has a “legitimacy deficit.” Sending armed cops in large numbers to respond to computer alerts seems unlikely to help build confidence.

The company defends the efficiency of its system. This indicates many instances where ShotSpotter Alerts resulted in timely arrests or rescue of gunshot victims. But there is little independent evidence that it reduces crime overall. A study, published in April in the Urban Health Journal, found that “the implementation of ShotSpotter technology does not have a significant impact on gun-related homicides or the results of arrests.” The microphones on the streetlights are all great, but they are not a substitute for the information gathered from humans. â– 

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This article appeared in the United States section of the print edition under the title “Shot spotty”


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