When a gunshot goes off, police will tell you seconds matter, which is why for years, the gunshot warning technology called ShotSpotter has been so popular with police departments across the country.

“To know where the incidents of gunshots are taking place and to be able to respond immediately, as quickly as possible, is very important to the city,” Mayor Michelle Wu said Wednesday.

Now, a new report by the ACLU of Massachusetts is raising questions about the effectiveness of ShotSpotter. The ACLU said it analyzed 1,300 reports it obtained from Boston Police for so-called ShotSpotter activations between 2020 and 2022.

“In nearly 70% of cases, Boston Police officers found no evidence of gunfire in response to ShotSpotter alerts,” said Kade Crockford, director of the Technology for Liberty Program at the ACLU of Massachusetts. “The technology is unreliable, it is sending police looking for shooters in communities where there may not have even been a shooting.”

The ACLU has argued before that those police responses, paired with the way human analysis can be applied to the technology, can lead to an infringement on the civil liberties of people who live in the neighborhoods.

Dr. Eric Piza is director of Crime Analysis Initiatives and a professor at Northeastern University. He led what is believed to be the largest study about ShotSpotter, analyzing 15 years of data in Kansas City and Chicago.

“We essentially found the technology offers some procedural benefits, for example police officers arrive on scene a little bit quicker with ShotSpotter calls, however we didn’t find any improvements on public safety,” Piza said. “Shootings did not go down in the ShotSpotter areas after the installation of ShotSpotter, shootings were not any more likely to be solved in either city after the deployment of ShotSpotter.”

Roughly 18 months after police officials labeled gunshot detection technology as not “fiscally responsible,” an Indianapolis Metropolitan Police Department working group reversed course and recommended purchasing ShotSpotter services, according to a 2023 report obtained by Mirror Indy.

In 2021, against a backdrop of protesters calling for the city to defund the police, IMPD Deputy Chief Kendale Adams voiced his opposition to a proposal that would have allocated $730,000 to spend on a gunshot detection system.

“One of the things this proposal talks about is ShotSpotter. And we’ve looked at that technology. It’s an expensive technology,” Adams said at a July 2021 meeting of the City-County Council. “It’s continuing to be technology we look at, but at this time, it just would not be fiscally responsible.”

But by the following February, police officials said they would test the use of gunshot detection technology on the east side. That pilot, which aimed to test the capabilities of ShotSpotter and two other vendors, concluded at the end of 2022. Police did not release the results of that study.

Early one morning last May, on a bungalow-lined street in Avalon Park, ShotSpotter detected real gunshots: more than half a dozen rounds fired.

It was a busy night, and officers didn’t make it to the scene for more than half an hour. But when they arrived they found 24-year-old Aréanah Preston, a Loyola law student and Chicago police officer, fatally shot on her front lawn.

Late one night in January, on a residential block of Auburn Gresham, ShotSpotter detected what likely were just fireworks.

But the alert sent officers out looking for a shooter, and when they got there they heard a loud bang. One officer opened fire in the direction of a boy who had just set off a firecracker, but did not hit him…

The policing profession spends a lot of time discussing and studying programs and policies, and less time thinking about how they’re implemented. Why can a program that’s effective in one city be a disaster in another city? How much of a program or policy’s effectiveness can be attributed to the way it was implemented?

At the recent American Society of Criminology conference in Philadelphia, our organization convened a panel discussion on implementation with practitioners and academics. I want to share a few highlights from the session.

Former Camden County, N.J., Chief Scott Thomson discussed his experience implementing the Integrating Communications, Assessment and Tactics training program. One lesson he learned was that it’s important that the change not be optional. He made it part of the agency’s policy, and there were consequences for not following agency policy…