ShotSpotter: Police Departments No Longer Rely On Eyewitnesses

There are thousands of little sensors dotted throughout cities in the U.S. and they're listening for gun shots.

In the fall of 2003, a sniper was on the loose near Columbus, Ohio. He had already killed one person and shot at others who were driving in the area of the I-270. The Franklin Country sheriff’s department and FBI were at a loss on how to capture him. After exhausting nearly all their options, they turned to a little-known technology called ShotSpotter—sensors deployed around the city that detect the sound of gunfire to provide the exact location of the shots.

A few months later, a suspect, Charles McCoy Jr., was caught in Las Vegas. Data from ShotSpotter was used in the investigation, and he was eventually sentenced to 27 years in prison.

“ShotSpotter has been very specific to the point where it will give you a street number, not just a street block”

Nearly 10 years on, 70 cities around the United States are using ShotSpotter year round, including Washington D.C., Boston, Chicago, and Oakland. Police departments say it has proven to be an invaluable tool in gun crime investigations.

Founded in 1995, ShotSpotter invented a way to detect gunshots using acoustic triangulation, which riffed off seismic triangulation technology that had been helping scientists study earthquakes in real time for many years. Municipalities now subscribe to the service, which costs them $45,000 to $60,000 per square mile annually. When a loud bang goes off, sensors placed in undisclosed areas around town use an algorithm to determine if it’s a gunshot. If that’s affirmative, the system notifies ShotSpotter headquarters in Newark, California, where an analyst listens to the sound. “The human reviews it to make sure the computer got it right, but more importantly to add more context — to tell [the police] if this sounds like multiple gunmen or like a shootout,” says James Beldock, a Senior Vice President at ShotSpotter.

A report is then sent to the local police department, showing a red dot on a map that’s the exact location of the gunfire. The entire process is completed within 30 seconds. Dispatch units in the vicinity then head to the scene.

fireworks have sometimes been mistaken for gunshots

The speed, accuracy, and details that ShotSpotter provide have changed the way that police departments deal with gunshots on a number of levels. First, knowing whether the gunfire came from a single person or multiple shooters—or from a pistol or a more powerful gun—has improved officers’ safety and helps them to formulate concrete plans of action. “That [information] gives the officer in the cruiser the ability to change his approach,” says Detective Sean Sullivan of the Springfield, Massachusetts Police Department.

Second, narrowing the location of a shot to within 25 meters allows first responders to arrive at the scene faster and to tend to victims. “ShotSpotter has been very specific to the point where it will give you a street number, not just a street block,” says Sergeant Monica McMenamin of the Atlantic City police department.

ShotSpotter also reduces the need for civilians to call for help. Sadly it’s fairly common that witnesses won’t call law enforcement to report gunfire unless they know a person has been hit. In one Springfield neighborhood, gang members were driving up and down the street with assault weapons, yet nobody called 911 “because it was social norm–they assumed someone else would call- or they’re so numb to the sound of gun shots that they just wait to see if someone gets hit,” says Sullivan.

Several private businesses and property owners decided to foot the bill for an expansion of ShotSpotter to that area. “They were very excited about putting it in their neighborhood because if [the sensor] goes off, they know there’s going to be a police response,” says Sullivan.

ShotSpotter even aids in recovering evidence after a shooting. In the past, police would rely on witnesses who could only provide approximate locations—or several witnesses who would each have different accounts of where the gunfire came from. Officers would then drive up and down the street looking for signs of a crime. ShotSpotter’s accuracy makes it “so you have a spot to start your search,” says Sullivan. “We’re in New England, so add in snow, and [that bullet] shell casings are the size of a cigarette butt. Try finding a cigarette butt in the snow in the middle of winter. It’s difficult, you know?”

In South Africa, it is being used to try to prevent illegal poaching of wildlife

According to Beldock, ShotSpotter promises clients that its system will detect and properly locate 80 percent of gunfire if it’s outdoors. There have been some issues over the years—namely that fireworks have sometimes been mistaken for gunshots and sensors have needed repair. “It’s not perfect—it’s technology,” says Sullivan. “The best computers out there will crash. You can’t expect it to be the end-all be-all, but if you use it properly it’s going to really help you.”

As of now, the sensors only respond to gunshots that are outside. Shootings that occur in buildings and motor vehicles are not detected. That could change soon, though. “That’s something that we’re very interested in,” says Beldock. “We’ve spent a lot of time looking at those scenarios. I think you’ll hear more from us about indoor gunshots.”

ShotSpotter has also been expanding its service to other countries, such as Brazil, Panama, and the U.S Virgin Islands. In South Africa, it is being used to try to prevent illegal poaching of wildlife. Sensors have been placed in Kruger National Park, where the system faces a slightly different problem than in urban areas. “You don’t worry about the tall buildings in the middle of the African savanna, but you do worry about the elephant that will knock your sensor over,” says Beldock.

Some cities have now started integrating ShotSpotter with surveillance cameras. When ShotSpotter is triggered after a gun blast, the camera at the location pans and zooms to the location of the sound. Over a 4G network, the live footage is streamed to a nearby police cruiser, where officers can view it. “They may have the ability to see the shooter and see a vehicle clear the scene,” says Sullivan.

In times when budgets are tight and police departments are stretched thin, law enforcement is embracing technology to help curb gun violence—a fact they’d like to be loud and clear.  “We want criminals in the community to know that we’re taking a proactive approach to crime fighting and we want them to believe we’re everywhere,” says McMenamin. “Most police departments are trying to do more with less, so this technology is certainly a welcome addition in our crime-fighting efforts.”