How similar gunshot detection technology to what Philly police are using looks in other cities.

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Philadelphia Police started using SENTRI January 1, which was not exactly the ideal day given SENTRI is a technology designed to detect the sound of gunshots. These sensors, connected to surveillance cameras and installed to help police officers answer the recurring question of “gunshot or firework,” were inundated with New Year’s Day fireworks after New Year’s Day fireworks.

It’s gotten better since then, police say. The department has continued using the technology as part of a nine-month pilot program. More than gunshot detection, they want SENTRI to be a tool that helps them catch criminals on camera and collect data. Right now, the city has 20 surveillance cameras equipped with these audio-detecting sensors, spread throughout some of Philadelphia’s highest-crime areas.   

Philly has been using video technology for years but is late to the audio game. Camden has audio sensors and so do New York City and Washington DC. They’ve been using a better-known technology called ShotSpotter, which adds another wrinkle to this story.

City Council President Darrell Clarke and others from Council were in talks with ShotSpotter officials last year and even made a trip to Camden to better learn how it works. He and Councilman Curtis Jones introduced a resolution earlier this year to further discuss ShotSpotter and “similar crime prevention tools.” At the time this resolution was introduced, the police department’s pilot program for SENTRI had been underway for two months, and yet it wasn’t mentioned. SENTRI has notably failed in other cities, including Wilmington. If City Council members read this article, it could be the first time they’re learning anything about a technology that allows the police department to further surveil Philadelphia’s citizens.

“The long story short around the country,” said Shahid Buttar, director of grassroots advocacy with the Electronic Frontier Foundation, “is police departments have generally procured surveillance technology absent any oversight.”

Jones would like to know more about whether the technology has been working and, if it proves successful, would like to see more urgency with getting it in Philadelphia.

“Second floor, fourth floor problems, I’m not getting into that,” said Jones, referring to the levels of City Hall featuring City Council and the Mayor’s administration. “I just want it in my neighborhood. Yesterday.”

Years behind schedule

Gunshot audio technology entered the Philadelphia news cycle last year, but it had nothing to do with what the police department started using. It had to do with ShotSpotter. Clarke and other Council members visited Camden last March and watched how the technology worked from the Camden Police Department’s Real-Time Tactical Operations and Information Center. He said he wanted a hearing quickly so a ShotSpotter pilot program could be a piece of the upcoming budget.

“We’re ready to get the checks out,” he said.

By then, a $500,000 check had already been cashed. Then police commissioner Charles Ramsey told the Inquirer the department was preparing to test a different system but didn’t identify the technology or how it worked. The police were years behind schedule.

In 2010, Senator Bob Casey and Congressmen Chaka Fattah and Bob Brady had helped secure a grant for the Philadelphia Police “to purchase a ShotSpotter Gunshot Location System (GLS) that calculates the position where a gun was fired and sends data to a central server accessible by law-enforcement agencies. This will decrease police response time, increase officer safety, and save numerous live.” The grant languished for years, and plans were reworked. Rather than get ShotSpotter, the police got SENTRI.

“It just didn’t match what we needed to do,” Mike Vidro, public safety special projects for the police department, said of ShotSpotter. “ShotSpotter’s ability is to write a lot of articles and get marketing behind it.”

SENTRI’s successes and failures

Hundreds of police and thousands of citizen SafeCam surveillance cameras are positioned throughout Philadelphia. SENTRI technology has been attached to 20 of them in 12 different police districts, according to the department. They’ve been placed in areas with high crime rates and are easily movable.    

“If 13th and Market is hot this week, we can put the sensors in,” said Ray Hayling, deputy chief information officer. “If it moves to Parkway, we need to have ability to take the sensors out and move them as well. If we’re chasing crime data we need to respond quickly.”

Here’s how the system works: The sensors have been calibrated to detect sounds similar to gunshots. When they pick up such a sound, the cameras turn in the direction from which it came. At the Real Time Crime Center, employees can instantaneously watch the scene to see if they can find the shooter or confirm whether it’s likely an actual gun shot went off based on actions of people in the area. When confirmed, police or medical personnel are dispatched to the area to look for suspects, victims, witnesses and shell casings.

For shootings detected by the technology, Vidro said officers have arrived three minutes to nine minutes faster than a 911 call.

“It’s amazing to me,” he said. “There are two guys out there literally firing for two minutes. It took somebody four to five minutes to call 911.”

False alarms happen. In the first couple of months, they accounted for about 80-90 percent of the sounds registered. What can set it off? Slamming manhole covers, garbage dumpsters, loud trucks. In North Philly last month, a detector went off when a bird hit a power line and fell dead on the hood of a car.

Vidro said the system has become more accurate recently, but the department isn’t treating it as an alarm system. He said the department is treating SENTRI as a tool and a test for whether they’re able to generate more evidence at crime scenes because of its presence.

The combination of camera and SENTRI audio sensor is around $15,000 to $20,000, according to Vidro, and it’s a one-time cost. ShotSpotter sensors cost about $60,000 to $75,000 a year per square mile. Cities similar to Philadelphia have used it cover 10 miles or more, meaning the cost could be around $750,000 annually. The grant wouldn’t have covered more than one year of ShotSpotter.

ShotSpotter, which can also be paired with cameras, works differently. Dozens of sensors are placed on government buildings or street poles — as opposed to one device set up with a camera for SENTRI. They record sounds that are transmitted back to ShotSpotter’s headquarters in California, and the company’s employees alert local authorities when sounds are determined to be gun shots. Its accuracy has ranged from below 1 percent to 50 percent to 97 percent and about anywhere in between.

Cities like Chicago, Richmond, Calif. and Wilmington have started using ShotSpotter after using SENTRI. A SENTRI system installed on 18 street corners in Wilmington did not record a single shooting scene from 2012 to 2014 and was regarded by Wilmington Council members as a waste of money.  

Neither former Mayor Michael Nutter nor Mayor Jim Kenney has expressed much interest in ShotSpotter, according to the company’s CEO, Ralph Clark. He said he met with members of Kenney’s administration earlier this year and they made it clear they didn’t want to consider ShotSpotter.

Rather than follow an installation plan put forward by SENTRI, they sought a third-party manufacturer. Vidro insists their system is working where Wilmington’s failed. Michael Cochrane, police chief inspector, said the department would like to add more audio sensors if they get more funding after the pilot program.

“Right now,” he said, “we’re happy with it.”

The push for urgency

Technology like ShotSpotter and SENTRI has been used to not only help police detect gunfire but go an extra step. In Oakland, a conversation picked up by ShotSpotter was used in trial to help convict someone of homicide. Situations like these concern Buttar, who worries about whether mundane conversations would be routinely picked up from audio sensors. It’s one reason, he believes, why transparency is needed.   

“All of those rights have been derogated pretty wildly by other departments using similar tools,” Buttar said. “We would hope policy makers in Philly are paying attention to that history.”

Jones, who along with Clarke called for the ShotSpotter hearings, says he doesn’t know much about the different brands and mainly just wants more information. Clarke spokeswoman Jane Roh said Clarke is still hoping to get a committee hearing scheduled for ShotSpotter in the next term. But Clarke and Jones also called for a hearing in 2015.

Jones’ district, he said, includes an area in West Philly where on average someone gets shot about once a month. He knows people are often reticent to call the police after gun shots, and he’s seen criminals use technology, to the point where one group was using a drone to tell where law enforcement was deployed.

This is why he’s been pushing for more information about a technology he hopes the city can successfully use against criminals.

“Bureaucracies,” Jones said, “unfortunately move more slowly than good ideas.”

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...