The DNAinfo archives brought to you by WNYC.
Read the press release here.

Police Expand ShotSpotter Program That 'Listens' For Gunshots

By Kelly Bauer | September 8, 2016 8:39am
 This image shows how ShotSpotter works.
This image shows how ShotSpotter works.
View Full Caption

CHICAGO — Chicago Police will expand a program that uses a sound-based GPS system that "listens" for gunshots and reportedly allows officers to respond quicker.

The program, called ShotSpotter, now will monitor both the Englewood and Harrison police districts, covering 13.5 square miles, according to a Chicago Police news release. Those districts have seen the "majority of gun-related violence" this year, police said.

The department also will expand its Police Observation Device camera monitoring, increasing the "footprint" of the cameras by 25 percent in the two districts, police said.

ShotSpotter electronically monitors for gunshots, giving officers a five-minute lead on responding to violence than typical 911 calls, police said. Police hope the expansion will allow officers to collect more evidence and information about shootings.

"CPD will continue to use every available resource to fight gun violence in our city," Chicago Police Supt. Eddie Johnson said in the news release. "This technology allows us to police smarter and be more proactive than reactive when it comes to responding to and investigating shooting incidents across the districts."

ShotSpotter had previously been available in 1.5-square-mile patches in the Englewood and Harrison districts.

When the technology was introduced in 2012, then-Supt. Garry McCarthy said it could tell the difference between fireworks, backfires from vehicles, and gunshots within seconds of the noise.

“It’s very, very accurate. Not only do we learn where the shots are being fired but now those officers can actually turn cameras on the location, get actionable intelligence that they can feed to the officers in the field as they're approaching," McCarthy said at the time.

The devices have raised some privacy concerns, though, from people worried about authorities listening to private conversations.

In a posting at the American Civil Liberties Union site, ShotSpotter CEO Ralph Clark says that the system works by placing 15 to 20 sensors per square mile, each containing a microphone, GPS, and a transmitter. The sensors are placed as low as 20 feet above the ground though "it's better for us the higher they are" because ambient noise "complicates" the effectiveness, Clark said.

Audio is recorded and stored for only a few hours or days, he said. When the sensor detects a gunshot-like noise it sends a report to a centralized location. The company's privacy statement says the system "is intentionally designed not to permit 'live listening' of any sort."

Human voices do not trigger ShotSpotter sensors and the devices do not have "high gain, directional or other specialized microphones," the company says.

ACLU senior policy analyst Jay Stanley concludes, "I am not losing sleep over this technology at this time. But I am concerned over the precedent of allowing our cities to be sprinkled with live microphones that are not subject to transparent operation, and where that will lead over coming years and decades."