When City Council gets back in session this September, expect the members to discuss ShotSpotter. Maybe you’ve heard of it. It’s a listening device that detects gunfire and reports to police so officers can investigate.

Jane Roh, director of communications for Council President Darrell Clarke, said while no date has been confirmed, the Public Safety Committee will likely schedule an information-gathering hearing this fall. In April, Council members already attended a demonstration from the Camden police about ShotSpotter. The likely forthcoming meeting is a sign that Philadelphia could be getting closer to getting ShotSpotter.

Why does Clarke want it? How does it work? And does it work well? Billy Penn explains this technology and its possible place in Philadelphia in ShotSpotter 101.

How did Philly become interested in ShotSpotter?

A few months ago, Clarke attended a gun violence prevention conference in Baltimore. He spoke about the safe passage of students to and from school in high-crime areas. David Chipman, senior vice president of public safety solutions at ShotSpotter, was speaking about the product. Chipman says Clarke invited him to Philadelphia so they could speak in greater depth about SpotShotter. In March, Clarke first proposed implementing a pilot program of ShotSpotter. Since then, not much has happened aside from the demonstration in Camden.

So I know it detects gunfire. How does that work?

A ShotSpotter system consists of about 15 to 20 small devices per square mile placed on buildings or street poles. The devices record sounds and send them back to a computer programmed with software to filter those sounds. When a sound resembling a gunshot is picked up, the file is sent within 30 seconds to acoustical experts at ShotSpotter’s headquarters in California. They work to verify if the sound was gunfire. If they do, they alert the necessary local police department, which can also view the soundwave.

Chipman says gunfire soundwaves travel farther than those of similar noises, like firecrackers or loud trucks, motorcycles and cars. Police dispatchers have said a gunshot wave usually looks like a sideways Christmas tree.

Can I see one of those sideways Christmas trees?

Yep. It’s the green soundwave pictured here.


Can it really tell if something is a gunshot all the time?

Not all the time. Sometimes shots go undetected and other times false alarms happen. Police in South Florida abandoned use of ShotSpotter for a time because of so many false alarms. The Miami Herald reported that in 2013 ShotSpotter verified 1,000 shootings and only 50 turned out to be real. Other departments have been pleased with the results. In Camden, use of ShotSpotter correlated with a 48 percent drop in gunfire from 2013 to 2014, and department leadership raves about the technology.

A 2011 study by CSG reported that dispatchers said they believed 67 percent of gunshots detected by the system were real gunshots. The range varied greatly between individual departments, with dispatchers in Richmond, Calif., placing the number at 97 percent, for instance, and in Nassau County, N.Y., at 50 percent.

Chipman says, “It’s not a perfect science…What we hear from customers is that our system is better than the human ear. In the areas people describe is that people hear so many things they don’t even call police.”

So these sensors listen to figure out where gun shots happen. Then what?

It’s up to the police, really. Chipman says departments have been able to use ShotSpotter to more accurately detect where a shot went off, allowing them to investigate quicker. The technology can give the location of a gunshot within 10 meters. Chipman says police departments have also been able to use ShotSpotter as a way to improve community outreach. Police can come to neighborhoods after a gunshot and check with residents about their safety and ideally prevent future crime by catching the people who are firing the shots and not just those who have guns. “We’ve imprisoned all this population,” Chipman says, “but the reality is in many of these areas that are dangerous people are probably  making the decision it’s safer to arm themselves — even if it’s illegal — than get shot. So we want the police to target the actual people pulling the triggers.”

Is there a good possibility Philly will get it?

Clarke has been the most powerful man in City Council for some time. He arguably has more power than the mayor. His influence bodes well for Philadelphia getting ShotSpotter, as does the success and increasing presence of the product. Pittsburgh, Camden, New York and many other cities have it.

As with nearly everything, money will be a factor. ShotSpotter costs between about $60,000 and $75,000 per year per square mile. If Philadelphia were to follow the steps of other cities, it would like install technology for three to four square miles at first and, if officials like it, install ShotSpotter in a total of about 10 square miles. The annual cost would be about $750,000. And that estimate wouldn’t include the cost of man hours. Police will have to be assigned to check on all the gunfire detected by ShotSpotter.

Will they be installing these devices on the wall of my house?

No. They can’t do that. ShotSpotter is installed on government buildings, like schools.

OK, most important question: what about gunshots or fireworks? Will police no longer have to play that game every summer?

ShotSpotter will certainly help, but it won’t completely solve the conundrum. Says Chipman: “On New Year’s Eve and the Fourth of July our system is almost melting just because of the tons and tons of alerts. There are some fireworks called machine guns. They’re purposely designed to sound like gunfire.”

Mark Dent is a reporter/curator at BillyPenn. He previously worked for the Pittsburgh Post-Gazette, where he covered the Jerry Sandusky scandal, Penn State football and the Penn State administration. His...