Are Gunshot Detection Systems the Answer to Rising Gun Violence?

vigil gunshot victim — Friends, family and residents of Chicago's Logan Square neighborhood attend a vigil for 10-year-old Lena Nunez on June 29, 2020. Nunez was shot and killed by a stray bullet while watching television with her brother in her grandmother's home. Gun violence soared in Chicago in 2020. Scott Olson/Getty Images

In 2020, more than 4,000 people were victims of gun violence in the city of Chicago. That number was almost 1,500 more from the year before. Those 4,000 were just part of the story in a particularly (if not historically) violent year in the Windy City, which reported a staggering 769 homicides in 2020, a more than 55 percent jump from 2019.

Chicago, of course, is not alone among U.S. cities struggling against a rising level of violent crime, much of it gun-related. The surge has put a spotlight on one possible tool to combat the problem, a decades-old technology that, these days, can almost instantaneously root out the location of a gunshot and quickly dispatch law enforcement to the scene.

President Joe Biden recognized the lure of such tech in June 2021 when he trumpeted money from the American Rescue Plan that he said could be earmarked for "gunshot detection systems." He was referring to companies like ShotSpotter, a Silicon Valley firm that sells "acoustic surveillance technology" — read: hardware, software and an around-the-clock service that detects and pinpoints the location of gunshots — to law enforcement agencies.

No one is touting these systems as a cure-all to the nation's gun-violence problem. The epidemic has far too many causes and is way too deeply ingrained in society for one easy solution, no matter how well it does, or doesn't work.

But ShotSpotter, and other technology like it, could be a critical component in calming things down and turning back the swelling tide of violence.

"The goal is to improve public safety," says Ron Teachman, the company's director of public safety solutions and a longtime law enforcement agent in New Bedford, Massachusetts and South Bend, Indiana. "Getting the police to respond comprehensively and effectively. Enhance community trust. Improve community collaboration. And ultimately, reduce gun violence."

How Gunshot Detection Works

The ShotSpotter system, which is the major provider of gunshot detection systems to the civilian market, is based on an array of microphones that can detect, identify and wirelessly send an alert when a gun has been fired, alerting local law enforcement to the time and location of the shot within 60 seconds. (Other companies like Raytheon Technologies provide of gunshot detection systems to the armed forces.)

The number of sensors that are deployed in any given area depends on a range of factors, including architecture and topography. Engineers will map out an area, decide where the sensors should be located, and how many, then go about building the coverage.

ShotSpotter will place the sensors, first, on rooftops of government buildings (less red tape). They'll go for commercial and residential buildings next, with permission, and then may put these high-tech microphones at various heights along a streetscape, including on utility poles.

(ShotSpotter, though, only provides gunshot location with latitude and longitude, not on height.) Teachman says that, generally, an average square mile can be covered by 20 to 25 sensors, which are wired for power but send their alerts wirelessly.

When a gun is fired, several of these sensitive sensors are triggered, enabling the system to triangulate — Teachman says more often it's "multi-angulate" — the relatively exact coordinates of the sound. This all happens in seconds; even milliseconds.

The information is sped to a ShotSpotter Incident Review Center, where it's first analyzed by computer algorithms, flagged as a possible gunshot, and then listened to by humans sitting in a 911-type environment. Within a minute — often, it's something like 45 seconds — an alert is conveyed to police, via smartphone, desktop computer, laptop or even smartwatch, marking a precise location of the shot on a map. Authorities respond as needed, depending on local policies.

Refining the Technology

Over the years, the algorithms have been refined and now can differentiate between the sound of fireworks, say and an automatic handgun. The software has been improved to account for different atmospheric and weather conditions, and can single out a shot while discounting, for example, a car backfire. The program considers echoes and acoustic anomalies that may be unique to an area.

The system is not effective with suppressed sounds — a shot from a "silencer" on a handgun, from inside a vehicle, within an apartment, or against a human body — because the sound is not as widely available for the sensors to pick up. Still, if it's out on the street or in other public places like parks or schoolyards (in 2019, 66 percent of homicides in Chicago and 44 percent of shootings happened in streets or alleys), ShotSpotter will hear.

And when police are dispatched, they don't go to the place where a 911 caller alerted them. They go to where the actual shot was picked up by the sensors.

"We dispatch to the dot, which could be driveways, backyards, alleys, fields, parking lots. Going to the dot increases the likelihood of finding a victim, finding evidence, saving a life," says Teachman, referring to the pin on the alert map that marks the spot of the shot. "Many times, officers say, 'I rolled up in my car in the dark and got out and I was almost stepping on a spent shell casing.'"

How Effective Is It?

ShotSpotter and similar systems are not without critics. A recent report from the MacArthur Justice Center at Northwestern University's School of Law found that an alarming majority of ShotSpotter's reports turn up no proof of gunshots or of any gun-related crimes. The report, in effect, accuses ShotSpotter of sending cops on phantom calls, making situations worse.

"High-tech tools can create a false justification for the broken status quo of policing and can end up exacerbating existing racial disparities," Jonathan Manes, an attorney for the MacArthur Center and a driving force behind the report, said in a news release. "We needed to know whether this system actually does what it claims to do. It does not."

A July 2021 article in Vice, too, accuses ShotSpotter and police of monkeying with results to manufacture favorable evidence in court cases, an allegation the company denies. "ShotSpotter has never altered the information in a court-admissible detailed forensic report based on fitting a police narrative," the company says in a release. "The idea that ShotSpotter 'alters' or 'fabricates' evidence in any way is an outrageous lie and would be a criminal offense. We follow the facts and data for our forensic analysis. Period."

ShotSpotter — used in more than 100 cities worldwide, including big cities like Chicago, San Francisco, Oakland, Detroit and New York City — claims several success stories, including a 29 percent drop in homicides in the first year it was used in West Palm Beach, Florida; a 30 percent reduction in shootings over the first four months it was deployed in Cleveland, Ohio; a 26 percent reduction in violent crime in a hot spot in Las Vegas, Nevada; a 56 percent drop in the number of gun-violence victims over an eight-year period the system was used in Omaha, Nebraska.

According to the company, ShotSpotter increases the number of gun incidents that are reported, to the point that some 97 percent of external gunfire in a monitored area is identified by the system. (The vast majority of gunfire, ShotSpotter says, is not reported otherwise to police.) The company says the system also drastically cuts down response time, gets victims transported to hospitals more quickly, and improves investigation by pinpointing the location of the incident more accurately.

All the focus on gunshots, Teachman insists, has another hugely important benefit: Gunshot detection systems act as deterrents to the bad guys and help police officers better connect with the people whom they're trying to protect and serve.

"Ultimately, you reduce gun violence by identifying those perpetrators and bringing them to justice. When people start seeing police responding, you start building a community trust. And that's what we're hoping for," Teachman says. "It's not just a police response. We're not going to arrest our way out of the gun-violence problem. It requires a community engagement as well. But the community has to believe in the public safety officials that are working with them. And that's what we're in the business of doing."