ShotSpotter, a publicly traded Newark, California-based firm, markets its system of microphones and sensors as 97 percent accurate at detecting gunfire, although critics contend the claims have not been scientifically validated by studies that would show if it can tell the difference between gunfire, firecrackers and other loud sounds.

Company officials say the vast majority of incidents of gunfire would otherwise go unreported, and the technology allows police to get to the scenes of shootings faster than waiting to respond to 911 calls.

A new study from the MacArthur Justice Center at Northwestern University School of Law found that 89 percent of police deployments in response to ShotSpotter alerts did not lead to a report of a gun-related crime, while 86 percent produced no incident report of any kind.

Researchers looked at records from the Office of Emergency Management obtained through the Illinois Freedom of Information Act for more than 21 months starting with July 2019. They found the technology triggered more than 40,000 alerts that led to no reports of crime of any kind. That represents an average of more than 61 deployments a day.

Jonathan Manes, the attorney who led the study, argued that the Spotspotter system does not operate as advertised. High-tech surveillance technologies, he said, can exacerbate racial disparities in policing.

“Our findings are shocking,” Manes in a statement. “The ShotSpotter system in Chicago prompts thousands of deployments by police hunting for gunfire in vain. This system puts police on high alert and sends them racing into communities; but almost nine times of our ten, the police don’t turn up evidence of gun crime or any crime at all. It creates a powderkeg situation for residents who just happen to be in the vicinity of a false alert.”

Chicago is one of the largest sources of revenue for Shotspotter, whose $33 million, three-year contract with the city is due to expire in August. The study shows the system is almost exclusively installed in 12 police districts on Chicago’s South and West sides, leading to significant racial disparities.

Police districts with predominantly white populations have similar rates of 911 calls about gunfire that did not result in reports about guns. But thousands of unfounded Shotspotter alerts in Black and Latino neighborhoods creates potentially dangerous police encounters and produce inflated statistics about “supposed gunfire,” according to the Northwestern attorneys.

This week, MacArthur Justice Center attorneys filed an amicus brief in support of a motion by a Cook County assistant public defender on behalf of a coalition of community organizations — Brighton Park Neighborhood Council, Lucy Parsons Labs, and Organized Communities Against Deportations.

The organizations urged Cook County Circuit Judge Vincent Gaughan to “investigate and ascertain the reliability” of ShotSpotter reports of gunfire in the case of Michael Williams.

Williams, 64, faces murder charges in connection with the May 31, 2020, fatal shooting of 25-year-old Safarain Herring. His public defender has filed a motion asking Gaughan to exclude ShotSpotter records from evidence in the case.

Prosecutors allege Williams picked up Herring at an Auto Zone in the South Shore neighborhood as it was being looted amid protests following the killing of George Floyd in Minneapolis before shooting him in the head for an unspecified reason, the Chicago Sun-Times reported following his bond hearing.

“In this case,” the community groups’ argue, “the Court should conduct an especially searching review of the evidence for ShotSpotter’s reliability both because ShotSpotter has not been generally accepted as a source of evidence at prosecution and also because it has a tremendous daily impact on individuals who live under its surveillance.”

A spokesperson for ShotSpotter declined to comment on the MacArthur Justice Center report.

Chicago Mayor Lori Lightfoot said Monday that ShotSpotter technology was a “lifesaver” when combined with the city’s network of cameras and other technology used in the city’s Strategic Decision Support Centers.

“Number one, it allows us in real-time to understand what’s happened in any given location and dispatch people to help,” Lightfoot said. “Number two, in an environment where people are fearful, sometimes, of calling 911, for a variety of reasons, ShotSpotter allows us to understand that there are those challenges that are out there, where the calls for service don’t come we still are able to respond.”

The mayor told reporters real-time information from ShotSpotter and other technology, combined with efforts to win the confidence of crime victims and witnesses, has helped the police department achieve a 60 percent clearance rate for homicides in 2021 so far. (The clearance rate for 2020 as a whole was about 45 percent.)

“It’s been an incredibly important tool in our crimefighting arsenal because we are using it and integrating it with other technology,” Lightfoot said.

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According to a ShotSpotter company officials, 2020 saw a significant spike in the number of gunfire incidents detected by the technology compared to 2019.

The number of incidents per square mile was rose the most in the Midwest region, where the company reported a 58 percent increase in gunfire. A company spokesperson did not provide any Chicago-specific data when requested, but nationwide data shows the rate of shootings increased even more dramatically in the first four months of 2021.

Some of the roughly 10 percent of ShotSpotter deployments that reportedly wound up leading to firearms charges in Chicago have also led to high-profile fatal incidents.

In December 2018, Chicago police officers Conrad Gary and Eduardo Mamolejo were struck and killed by a train as they chased a suspect on the Metra tracks near 103rd Street and South Cottage Grove Avenue, where they had been dispatched to investigate a ShotSpotter alert. A man who said he had found a gun and test-fired it on the tracks before officers arrived was last month sentenced to one year in prison after he pleaded guilty to one count of aggravated unlawful use of a weapon.

And on March 29, it was a ShotSpotter alert that led Officer Eric Stillman to chase 13-year-old Adam Toledo down an alley in the 2400 block of South Sawyer Avenue. Video from the incident appears to show Toledo toss a handgun behind a fence moments before Stillman fatally shoots him.

According to police and prosecutors, 21-year-old Ruben Roman fired more than a half-dozen shots at a passing car before handing the gun over to Toledo. Roman faces charges of reckless discharge of a firearm, unlawful use of a weapon by a felon and felony endangerment of a child. A ShotSpotter alert directed police to the scene within about a minute of the initial shooting.

Freddy Martinez, a policy analyst at the Washington, D.C.-based nonprofit Open the Government and executive director of Lucy Parsons Labs, one of the groups behind Monday’s brief, called on the City Council to refuse to renew the city’s contract with ShotSpotter, citing the role of the technology in Toledo’s death and the Department of Justice’s report into the policies and practices of Chicago police.

Testifying under oath nearly four years ago, a ShotSpotter analyst admitted that the company’s claim of accuracy was “put together by our sales and marketing department, not our engineers,” Martinez noted.

Martinez agreed with Lightfoot that ShotSpotter is but one part of the city’s extensive public safety surveillance network. But he disagreed with the mayor’s suggestion that it has reduced crime.

“[The Chicago Police Department] has long promised violence reduction through the use of those and other forms of surveillance like predictive policing and facial recognition technology,” Martinez said in an op-ed published last week in South Side Weekly. “The truth is that none of these automated approaches address the root causes of crime—poverty, the criminalization of low-income and marginalized people, and the perverse priorities that divert desperately needed community resources to police budgets.”

Miguel Lopez, membership coordinator for Organized Communities Against Deportations, another of the community groups who filed the brief, said in a statement the city would be better served investing the $10 million a year it spends on the ShotSpotter system into the communities where it is deployed to help young people deal with conflict.

“Knowing very well that police officers tend to escalate all types of situations and are known to use excessive force,” Lopez said, “ShotSpotter technology creates an additional layer of violent response from police officers as they rush aggressively to poor, Black & brown neighborhoods expecting to be met with gunfire.”