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DENVER (KDVR) – Denver’s gunshot detection system led to the arrests of nearly 100 people last year and allowed officers to take 81 guns off the street.

So far this year, police recovered more than 100 guns because of ShotSpotter technology that detects gunshots in real time, records real audio, and alerts police to the potential gunfire within a 25 meter radius.

“The ShotSpotter has been a tremendous tool for us,” said Lt. Matt Clark, who works in Denver Police Department’s Major Crimes unit.

Since 2015, the police department has gradually placed the technology in new geographic locations. It is now in seven areas across the city. The department paid $815,544.50 this year for access to the service, according to DPD.

“When a detection gunshot goes off, it quickly triangulates to give you a precise location of that gunshot, and it will follow up with the number of gunshots,” said Joe Montoya, the Division Chief of Investigations for DPD.

The FOX31 Problem Solvers found arrests due to the sensors are up 296% since 2015 when the department first invested in the equipment.

However, that doesn’t necessarily indicate that gun crimes are going down in Denver.

According to Doug Schepman, a spokesperson for the DPD, aggravated assaults with a firearm in 2020 were up nearly 50% from the previous three-year-average.

“We actually found an increase of crimes that involved a firearm after the technology was implemented,” said Daniel Lawrence, a research associate at the Urban Institute.

The non-profit, non-partisan organization received funding from the National Institute for Justice to evaluate gun detection systems in Denver, Milwaukee, and Richmond, CA between 2015 and 2019, according to Lawrence.

The group, which published its findings last year, focused on Denver’s use of the technology between January 2015 and June 2016. Lawrence said the uptick in firearm crimes could have been a result of the technology alerting police to additional crimes.

“It gets police to the scene,” Lawrence said, explaining that the technology helped Denver officers respond 66% faster to calls when compared with typical 911 calls for service. “Denver was doing a pretty good job.” 

“One of the things we found particularly effective is having a manager,” he added. “The technology gets the officers to the scene, but it’s really the follow through with the investigation that’s critical as well as having a supervisor who makes sure that the investigation is happening.”

Lawrence also said the technology doubled the amount of shooting notifications that officers received, causing a greater workload on officers.

Clark and Montoya credit the ShotSpotter for helping them solve a homicide investigation in 2016, when one suspect said he shot another in self-defense after the victim first shot him.

However, Clark said the ShotSpotter captured evidence that revealed the suspect’s actions were actually retaliatory.

“He left the location and then came back and fired upon and engaged the victim,” he said. “It was vindictive. It was absolutely retaliatory for being shot.”

The ShotSpotter sometimes alerts on something that is not gunfire, in error.

Last year, it sent more than 2,500 alerts to Denver Police about potential gunfire.