Police sound out gunfire's source

Detection: Acoustical systems linked to computers are curbing the celebratory, and dangerous, practice of shooting into the air.

April 07, 2003|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

New Year's Day of 2002 in Baltimore was greeted by a fusillade of celebratory gunfire. Of the hundreds of bullets fired into the air, one fell and lodged in the forehead of 19-year-old Ferra Diggs as she watched fireworks at the Inner Harbor.

Diggs survived, but victims elsewhere haven't been so lucky. On July 4, Xavier Morales, 9, of Anaheim, Calif., was killed by a falling .22-caliber bullet as he watched fireworks with his family.

Similar incidents in recent years have killed children and adults in New Orleans, Kansas City, Mo., Detroit, Philadelphia and San Jose, Calif.

But police in several cities now say they've found a safe, effective way to curb the gunplay -- a new acoustical technology that allows them to pinpoint the source of the shots instantly.

Coupled with aggressive campaigns to warn residents that police are listening, the new devices have nearly silenced celebratory gunfire, and made the holidays safer for residents and for officers, police say.

"We don't ever want to go back to the way it once was," said Capt. Scott Warner of the Redwood City, Calif., Police Department.

The technology also is helping police reach crime scenes and victims more quickly. A new version, called On Alert, may soon be able to identify the make, model and caliber of the guns fired and trace a bullet's trajectory from start to finish.

"It's possible even to hear an impact sound such as that of a person," said Billy Robinson, chief executive officer of New Orleans-based Proxity Digital Networks, which makes one of the systems. "It's a matter of programming."

Although celebrating holidays by firing guns is a tradition as old as firearms, it's dangerous. Bullets leave the barrel at 300 to 3,000 feet per second. But like pop flies at a baseball stadium, they're immediately slowed by gravity and air resistance. Thousands of feet up, they turn and begin to fall.

The falling bullets gain speed until they reach "terminal velocity" -- when wind resistance equals the pull of gravity. That speed varies with the weight and shape of the bullet, but it can reach 200 to 500 mph -- more than enough to kill.

Gunshot detectors work by precisely timing the arrival of the sound of gunfire at an array of microphones installed several hundred yards apart on rooftops or utility poles. They're linked by telephone circuits to a police computer, which filters out slammed doors and most other innocent loud noises.

At least three sensors have to "hear" the shot. Knowing the sensors' exact locations, and the speed of sound, the computer "triangulates" -- calculating where the gun had to be for the blast to pass each sensor at the precise times it did.

In seconds, a red dot appears on a computer map of the neighborhood. "We can figure within 20 feet or so where it's coming from," said Warner.

Geophysicist Robert Showen developed ShotSpotter after noticing that his earthquake detection gear also picked up gunshots. He founded Trilon Technology to market the system and sold it to five cities.

Baltimore decided it was too costly -- more than $1 million for each police district, according to a police spokeswoman. Other cities have spent less by focusing the systems on problem neighborhoods.

The Phoenix suburb of Glendale, Ariz., covered 2 square miles for $277,500. Glendale police said they used to rely on residents to report gunfire. But callers could rarely say exactly where the shots came from.

This past New Year's Eve, when a new ShotSpotter system pinpointed an address where shots were fired, police found a man standing in a front yard. He denied any wrongdoing.

"But at his feet there was a collection of spent shell casings," said Detective Sergei Droban.

That provided the probable cause needed for a search. Officers charged him with carrying a concealed weapon and firing a gun into the air -- a felony.

Glendale's system also revealed that only 20 percent of the gunfire was being reported by residents.

"It's crazy the way people celebrate here," Droban said.

In a Redwood City neighborhood, the New Year was typically greeted by 25 minutes of continuous gunfire -- hundreds, perhaps thousands of shots. Police officers sometimes parked in garages or under bridges until the rain of lead stopped.

"Folks in the community were actually really scared," Warner said.

Then ShotSpotter was installed. "Last year, we had seven shots," he said. "It's just not a problem for this area anymore."

Police agree that ShotSpotter alone can't provide the probable cause needed for a search or an arrest. But in concert with aggressive publicity and warnings that shooters will be prosecuted, it has cut the gunfire.

Having the technology to back up the warnings, Droban said, "just fundamentally changed the problem."

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