A new analysis says police officers who respond to ShotSpotter calls come back empty — no crime detected — 86% of the time.
In a city where the sound of gunfire is virtually commonplace, ShotSpotter — with its ability to “hear” gunshots with 97% accuracy and immediately summon the cops — would seem to be a godsend.
But a new analysis questions that claim of near-perfect performance. Police officers responding to calls from ShotSpotter, according to the study, report no evidence of a crime 86% of the time.
Our concern is threefold. First, we believe a gunfire detection system that costs taxpayers $33 million ought to have better results.
Second, sending cops out on what amounts to thousands of false alarms is a huge waste of their time.
And, above all, we don’t like the notion that officers are being sent into neighborhoods thinking there is a dangerous emergency when, in reality, the call might have been triggered by noises misheard as gunfire by ShotSpotter. That can, in itself, create a tense situation.
“It sends police racing into communities searching, often in vain, for gunfire,” said Jessey Neves, a spokeswoman for Northwestern University School of Law’s MacArthur Justice Center, which conducted the analysis, told Sun-Times reporter Tom Schuba. “Any resident in the area will be a target of police suspicion or worse. These volatile deployments can go wrong in an instant,” she said.
Given what’s at stake, City Hall should start asking serious questions — and demanding answers — about ShotSpotter’s effectiveness.
Police defend ShotSpotter
MacArthur Justice Center researchers say 40,000 ShotSpotter alerts between July 2019 and mid-April wound up with no report being filed by responding officers. Only 10% of the alerts likely involved guns.
The system covers 117 square miles of the city, approximately half of Chicago’s landmass.
Despite questions raised by the MacArthur analysis, the Chicago Police Department praises the system’s effectiveness.
“ShotSpotter has detected hundreds of shootings that would have otherwise gone unreported,” police spokesman Thomas Ahern said, adding that the system “is helping us reduce crime and make our neighborhoods safer.”
And, to be sure, ShotSpotter has helped the police locate gunmen and shooting victims since going citywide in 2018.
Last month, for instance, a ShotSpotter detector directed officers to 82nd Street and Coles Avenue, where they found and rushed to the hospital Swaysee Rankin, a 15-year-old boy who had come to the aid of his 10-year-old friend when she was shot a block from the same location just six months earlier.
But questions about ShotSpotter’s accuracy have plagued the technology for years.
In a 2017 attempted murder case in San Francisco, a ShotSpotter forensic analyst testified that his company’s accuracy computations did not come from engineers, but from the sales and marketing department.
“We need to give them [customers] a number,” the analyst, Paul Greene, said. “We have to tell them something. … It’s not perfect. The dot on the map is simply a starting point.”
Detroit is in its first month of a four-year contract that has put ShotSpotter monitors on the city’s north and northeast sides. But one Detroit police commissioner, Willie Burton, voted against the contract precisely for reasons that should give Chicago pause, too.
“The sensors will detect gunfire in a 100-yard radius, and then the police will look at any person in that radius as a potential suspect,” Burton said. “I just think it could lead to police profiling Black men just because they live in areas with heavy gunfire.”
Variables affect accuracy
While the system is sold to police departments as a near infallible law enforcement partner, Paul Greene, the ShotSpotter expert, testified in San Francisco that a host of factors effect its reliability, including topography, temperature, humidity, wind speed, how often the equipment is calibrated, and the skill of the humans interpreting the sounds picked up.
Chicago’s ShotSpotter contract expires in August. CPD hasn’t decided whether to renew its agreement with the company, but before the department does so it had better ask a lot of questions — and make all the answers public.
What City Hall and CPD should not do is downplay questions about the gunfire detection system, which Mayor Lori Lightfoot effectively did this week when she questioned whether the MacArthur Justice Center research is “actually accurate.”
Lightfoot should put that question to ShotSpotter, not to the MacArthur Justice Center.
What’s Chicago really getting for its $33 million?
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