If ShotSpotter is a good crime-fighting tool, the police must provide proof

Chicago police tout ShotSpotter, a technology that senses gunfire and summons police, as an important crime-fighting tool. But in a scathing report this week, the Chicago inspector general’s office said police records are too incomplete to verify that claim.

The police department, as a first step, should do a better job of tracking what happens after ShotSpotter sounds an alarm.

Ideally, anytime there is a shooting in those parts of the city where ShotSpotter is installed, police will get there quickly enough to apprehend culprits and aid victims. If that happens often enough, the police could justify the $33 million that has been spent on ShotSpotter in the past three years, with a recent two-year renewal.

But at the end of its report, the IG’s office said police record-keeping, including so-called investigatory stop reports, is just too limited to give a clear picture of how much ShotSpotter helps police — its so-called operational value.

And it’s not just the IG’s office that’s asking questions about ShotSpotter. Ald. Roderick Sawyer (6^th) told us he and other City Council members want to learn more about the inner workings of the system and associated data, so the city can use it most effectively.

ShotSpotter is operating in 12 police districts, mostly on the South and West sides. The IG’s office examined 50,176 ShotSpotter alerts from January 2020 through May. Police documented a response to those alerts 42,000 times, but officers wound up making “investigatory stop reports” — essentially confirming gun-related criminal activity — only 9.1% of the time. Other reports referenced the technology but didn’t correlate with a specific ShotSpotter notification.

Various reasons could account for that. The shooters and witnesses could have left the scene before police arrived. Responding police might have chosen not to search the area for shell casings, which are evidence of gunfire but don’t show whether bullets were flying moments or days before police got there.

Without more complete reporting — and this is crux of the problem — it’s hard to judge whether responding to ShotSpotter alerts is the best use of police time.

According to the Brookings Institution, data from Washington, D.C., and Oakland, California, show that people call 911 only 12% of the time when there is gunfire. The Chicago police department says ShotSpotter has detected hundreds of shootings that otherwise would have gone unreported. The department says ShotSpotter is “crucial” because it flags incidents when no one calls 911, giving them a chance to “respond more quickly to locate and aid victims, identify witnesses and collect forensic evidence.”

But the IG’s office says the record-keeping isn’t good enough to show how frequently that’s happening, which rules out a dependable cost-benefit analysis.

The concern over ShotSpotter is part of a larger debate that Chicago and other cities are having over striking a new balance between civil rights and privacy and how police forces work to keep us safe. Cameras in public places, especially cell phone cameras, now frequently document how police behave. Recently developed DNA technology has showed some people have been wrongfully convicted. The evidence has mounted that reforms of police practices are necessary.

Struggling with the pros and cons of ShotSpotter resembles the debates over having police officers in schools and how authorities (not just the police) should respond to calls involving somebody who might be mentally ill. Just on Wednesday in Chicago, there were news stories on all of these issues.

Going forward, city officials will have to decide whether to keep using SpotSpotter or change the system or discontinue it. To get that decision right, police need to sort how often, in incidents where no one else notifies police of a shooting, ShotSpotter leads to an arrest, helps solve a case or assists a victim.

That’s critical information in a city where bullets fly every day.

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