A new report from a Washington, D.C.-based think tank shows that the gunshot detection technology Denver and other cities use is a beneficial law enforcement tool, but only under proper protocols.

The Urban Institute evaluated the police departments in Denver, Milwaukee, and Richmond, California, and concluded that from 2015-2016, violent and firearm crimes increased while the number of arrests also increased.

Denver’s ShotSpotter system involves acoustic sensors that detect and analyze potential gun shots, then send the tape of potentially real gunfire to a human analyst, who finally alerts local dispatchers. This process takes 60 seconds or less.

“We do fairly regularly show up and find victims that have been shot and no one has called 911 yet and we get there first and we can get them medical attention,” Denver Police Commander James Henning told CPR. 

This year the Denver Police added ShotSpotter sensors around the Ballpark, Union Station and Civic Center Park. ShotSpotter now covers approximately 12% of the city.

Chief Paul Pazen said that the gunshot detection technology contributed to 134 arrests since 2015.

The Urban Institute recommended that ShotSpotter come with accountability procedures, such as having police personnel return to a scene if an initial check does not turn up any bullet casings.

Communication with the public is also key, both to dispel the myth that police can listen in to anything happening in a neighborhood as well as to remind residents that ShotSpotter is not a substitute for calls for service.