Broward Sheriff's tech tool has an ear for crime
By Ihosvani Rodriguez, Sun Sentinel
fl-shot-spotter-20101127
POMPANO BEACH —
The walls have ears here.
They come in the form of 39 gadgets that resemble coffee cans and are placed on outside building walls. They are spread over 2 square miles of a high-crime area where gunfire often is part of the ambient noise.
For years, law enforcement agencies have depended on surveillance cameras to help fight crime, but for the last eight months, the Broward Sheriff's Office has been testing a $500,000 audio-surveillance system that has yielded several arrests.
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The gunfire detection system, called the ShotSpotter, was credited most recently in the arrest of four men who, deputies say, took part in a home-invasion robbery.
http://www.sun-sentinel.com/news/local/crime/fl-shot-spotter-20101127,0,6380139.storyAt 3:16 a.m. on Nov. 15, the network of sensors picked up five gun shots and sent an alarm to sheriff's dispatchers sitting miles away. The sensors used GPS to triangulate and pinpoint where the shots were fired.
The system is so accurate, it directed deputies to within 30 feet of where the bullets were fired, said Sheriff Deputy Detective Bryan Holmes, who oversees the department's system.
"The most useful thing about this is that it's live. We don't have to wait for a neighbor or a passerby to call us," said Holmes. "We find the place immediately. We save time in responding, time that could be the difference between somebody living or dying."
The first deputy arrived at the house on the 1400 block of Third Way at 3:18 a.m. — exactly two minutes after the gunshots were first heard. The deputy quickly realized he had come upon a home-invasion robbery in progress, according to a report.
The use of ShotSpotter is spreading across the country as law enforcement agencies embrace technology to keep up with the bad guys.
Law enforcement agencies nationwide have installed 65 ShotSpotter systems. In Florida, only the Broward Sheriff's Office and the Riviera Beach Police Department are using the equipment.
A big drawback for other units has been the price of the acoustic gunfire tracking system itself, starting at about $200,000 per square mile covered.
The FBI loaned the system to the Sheriff's Office in April. They picked a spot in Pompano Beach because of its high gunfire rate, officials said. Sheriff's administrators will have to decide by next April whether to return the equipment, or invest in it.
One academic who studied a similar system in Virginia warned in 2008 that law enforcement shouldn't rush to spend tax money on it just yet.
"A fiscal downturn forces us to look at what is the rational use of police resources. Do we want more police cars? More officers? Or do we look at something like the ShotSpotter," said Peter Scharf, a professor at Tulane University. "The problem is that this technology has not been fully proven. More research has to be done before governments spend such enormous amounts of the public's money."
Scharf's report to the National Institute of Justice called the system useful, but took issue with an apparent high rate of false calls. The 2008 report concludes with a call for further independent testing.
Company and sheriff officials say the technology has advanced since then.
An early problem they say has diminished was that the system picked up noises like firecrackers or a car backfiring, and mistook them for gunfire. Broward's system has been triggered by helicopters and downshifting trucks from nearby Interstate 95.
Critics fear continual false alarms may cause authorities to respond less aggressively to a ShotSpotter alert than to a 911 call from an eyewitness.
Holmes says Broward's system has learned to distinguish gunfire from bottle rockets. To teach the ShotSpotter software, Holmes goes through each of the sound files every week and tells the computer what he thinks triggered the sensors. The computer then rejects sounds that match those made by non-weapons.
"As time goes on, the ShotSpotter gets smarter, and soon it'll only ring an alarm when it's actual gunfire," he said.
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