Once a gunshot-like sound occurs, ShotSpotter plots the noise on a map and notifies police dispatchers. Credit: Sebastien Malo/Flickr

It’s hard to say where McGruff the Crime Dog would land on the ShotSpotter debate, but I bet he would commend its intentions.

Let’s back up: If you don’t live in one of the more than 90 cities across the country that employs this high-tech surveillance system, you might not know what it is. ShotSpotter is a gunshot detection technology that’s marketed to reduce gun violence. It uses a network of microphones installed around a city or neighborhood – on rooftops, street lamps; basically anywhere up high.

The idea is that once gunshot-like sounds occur and three or more sensors pick up the sound, ShotSpotter plots the noise on a map and notifies police dispatchers. Officers then rush toward the location, ideally to catch the shooters, help victims and/or collect possible evidence.

Sounds good in theory, right? Unfortunately, in practice, police often come up empty-handed because people rarely stick around after firing a gun. And while the technology has been used as evidence in court in a handful of states, it generally plays a minor role for prosecutors and police trying to reduce gun crime.

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On this episode of Reveal, reporter Matt Drange takes a closer look at ShotSpotter by digging into thousands of alerts in cities across the country. A clear pattern emerged: lots of calls, few tangible results.

Take San Francisco, for example, where there were more than 3,000 ShotSpotter alerts over a two-and-a-half-year period. Of those, two resulted in arrests. And only one was gun related.

Nationwide, the system is costing taxpayers millions of dollars each year. We wanted to find out: What’s the public getting in return?

For more of our stories on the manufacturing, regulation and trafficking of guns, go here.

Julia B. Chan can be reached at jchan@cironline.org. Follow her on Twitter: @juliachanb.

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Julia B. Chan worked at The Center for Investigative Reporting until June, 2017. Julia B. Chan is a producer and the digital editor for Reveal's national public radio program. She’s the voice of Reveal online and manages the production and curation of digital story assets that are sent to more than 200 stations across the country. Previously, Chan helped The Center for Investigative Reporting launch YouTube’s first investigative news channel, The I Files, and led engagement strategies – online and off – for multimedia projects. She oversaw communications, worked to better connect CIR’s work with a bigger audience and developed creative content and collaborations to garner conversation and impact.

Before joining CIR, Chan worked as a Web editor and reporter at the San Francisco Examiner. She managed the newspaper’s digital strategy and orchestrated its first foray into social media and online engagement. A rare San Francisco native, she studied broadcasting at San Francisco State University, focusing on audio production and recording. Chan is based in Reveal's Emeryville, California, office.