A new study has differing results for the same gunshot detection technology used by the Sacramento Police and Sheriff's departments.
The technology uses sensors that work together to identify the site of a gunshot to within a couple of feet.
Daniel Lawrence is one of the authors for the Urban Institute who looked at the use of the technology in the Bay Area, Denver, and Milwaukee.
"What we found in Richmond, California, is that officers, they're going to respond to gunshot detection alerts about 15 percent faster than they will to 911 calls for service. That's about 30 seconds to three minutes," Lawrence said.
Richmond saw an 18-37 percent decrease in violent crime in areas that had sensors. Milwaukee had some decreases. Denver had no change. The researchers say success depends on the ability of a department to communicate with the public, train with the technology, and thoroughly investigate once a notification is made.
Sacramento Police started using the technology from the private, for-profit ShotSpotter company in 2015. Since then, it has been notified of gunfire 1,136 times by ShotSpotter sensors, compared to just 360 notifications through 911.
Officer Karl Chan says the technology also helps the department because the community sees a quick response.
"It helps us pinpoint to where the shots are actually happening and actually give a better response to the community that's affected by it," Chan said.
Sacramento County Sheriff Scott Jones says the notifications have helped solve other crimes.
"If there was no real crime other than the gunfire being committed, we can still compare the brass, those shell casings with other potential crimes where perhaps there was a victim,” Jones said.
Jones says there were four deputies assigned to respond to Shot Spotter alerts. But because of budget cuts, deputies are now responding to notifications when they can. The county sheriff has a contract with ShotSpotter for sensors and notifications that expires in March.