May 29, 2012
MOUNTAIN VIEW, Calif. — At 7:22:07 p.m. on a recent Thursday, an electronic alarm went off in the soundproof control room of a suburban office building here.
A technician quickly focused on the computer screen, where the words “multiple gunshots” appeared in large type. She listened to a recording of the shots — the tat-tat-tat-tat-tat of five rounds from a small-caliber weapon — and zoomed in on a satellite map to see where the gun had been fired: North 23rd Street in Milwaukee, 2,200 miles away.
At 7:23:48, the technician, satisfied that the sounds were gunshots, sent an alert to the Milwaukee Police Department. Less than two minutes later, or at 9:25:02 p.m. Wisconsin time, a tactical team arrived at the address to find five .22-caliber shell casings and a bleeding 15-year-old boy who had been shot in the arm. The casings, said Chris Blaszak, a detective assigned to the department’s intelligence fusion center, were found within 17 feet of where the alert had placed the gunman. Total elapsed time: 3 minutes, 55 seconds.
Milwaukee is one of an increasing number of cities around the country — just under 70 to date, including some in the New York area — that are using a gunshot detection system called ShotSpotter to pinpoint the location of gunfire seconds after it occurs. Last year, the company that developed ShotSpotter began offering a more affordable system, and that has brought in new clients and led other cities to consider trying it.
The detection system, which triangulates sound picked up by acoustic sensors placed on buildings, utility poles and other structures, is part of a wave of technological advances that is transforming the way police officers do their jobs.
But like other technologies, including license plate scanners, body cameras and GPS trackers, the gunshot-detection system has also inspired debate.
In at least one city, New Bedford, Mass., where sensors recorded a loud street argument that accompanied a fatal shooting in December, the system has raised questions about privacy and the reach of police surveillance, even in the service of reducing gun violence.