Sacramento police deploy microphones to listen for gunshots
July 30, 2015
The Sacramento Police Department is deploying new technology in an effort to reduce gun violence – a network of microphones that listens for gunshots in high-crime areas and sends the information to law enforcement.
Called ShotSpotter, the system is being used by 90 cities around the world, including New York, Boston and Oakland. Sacramento police deployed it last month in North Sacramento. Fresno also installed the technology last month.
At a news conference Thursday morning, Police Chief Sam Somers Jr. described ShotSpotter as “game-changing,” noting that it would decrease response time and allow officers to more accurately determine the location of gunshots.
“The main thing we’re looking at is deterrence,” he said. “Your odds of getting away with a crime like this are diminishing.”
ShotSpotter relies on a network of microphone sensors to listen and record noises in a specific area. If the sensor detects a high-pitched sound resembling a gunshot, acoustics experts from the company pinpoint the location and transmit the information to police.
The technology is sold by a Bay Area firm, SST Inc. Company President and Chief Executive Officer Ralph Clark said Thursday the location of gunshots is relayed to local law enforcement within a minute, and is accurate within 30 feet.
“We want to put trigger-pullers behind bars,” Clark said.
Since June, Sacramento has had 3 square miles in the north command area outfitted with ShotSpotter, representing 3 percent of the city’s total size.
Somers would not reveal specifically where the microphones are installed. After a yearlong pilot project, he said, the city will evaluate ShotSpotter. If it is successful at reducing crime, he will ask the City Council for money to expand it to other neighborhoods.
The sensors are expensive. The city of Sacramento will pay $50,000 per square mile of coverage area annually, not including a one-time $10,000-per-square-mile activation fee. The $180,000 needed to fund the pilot program is coming from the assets-seizure fund, Somers said.
Garen Wintemute, an emergency medicine doctor and professor of violence prevention at UC Davis, said the technology could bring some benefits to high-crime communities, noting that gunshots are often under-reported.
“Most gunfire does not result in injury,” said Wintemute, who is an expert in firearms. “If it’s a common occurrence, it might not be reported. If there’s a sense that it might not lead to change, it might not be reported.”
Clark said it can take significant effort and time to install the sensors because the company must obtain permission from public and private property owners. The equipment is usually placed on high floors to increase reach, but also because the microphones rely on cellular networks to relay information.
So far, ShotSpotter has detected an average of two gunshots per night in the city’s coverage area, according to Somers. In the past, he said, officers would have to rely on the reports of residents, which could be delayed or unreliable.
About 15 to 20 sensors are used per square mile, according to ShotSpotter. Computers are able to determine a location of the gunshot based on the time stamp from each sensor that detected the noise, Clark said.
Former Sacramento County Sheriff John McGinness said he considered ShotSpotter a decade ago, but the tremendous cost associated with the program was a deal-breaker.
“We were in a very tough fiscal cycle,” McGinness said. “We couldn’t justify the expenditure of resources when we were looking at layoffs.”
But, he said, “it could have a positive impact on saving lives.”
Sacramento police took about 320 reports of shots fired in North Sacramento during the first four months of 2015 – almost three reports each day, according to city police dispatch data. North Sacramento and Oak Park are the areas of the city with the greatest frequency of such reports.
When New York City police announced earlier this year that ShotSpotter would be installed in the Bronx and Brooklyn, some legal experts said the technology could raise issues of privacy, and whether incriminating sounds picked up by microphones would constitute warrantless search and seizure.
Somers said his department is having discussions with the Sacramento County District Attorney’s Office on how the data from the sensors could be used to obtain a search warrant.
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