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ShotSpotter: A Success Story for Law Enforcement Analytics

May 23, 2016



If you read my previous blog on predictive analytic tools for law enforcement, "Predictive Analytics for Policing: Overreliance on Violence Risk Prediction Scores," you may recall the quote I included from Fresno Police Chief Jerry Dyer that his “officers are expected to know the unknown and see the unseen,” Dyer said. “They are making split-second decisions based on limited facts. The more you can provide in terms of intelligence and video, the more safely you can respond to calls.”
Hesitation on Trusting the Analytics

When I wrote that blog post, I cautioned that any equation derived from empirically researched risk factors needs to be sufficiently sensitive to minimize the number of false negatives on law-abiding citizens. This would ensure profiles are not used. Our firm has always embraced the concept of a deductive, fact-based approach to investigate and assess the risk violence in our communities. And our thoughts on law enforcement analytics are no different.

I recently read a Washington Post article about a new tool – one that has been described as “the best way to measure gun violence in America.” ShotSpotter – a technology that listens for gunfire’s acoustic signature and then reports it to law enforcement – was implemented in 62 urban cities across the U.S. in 2015. The ShotSpotter system works by triangulating sound picked up by sensors placed on utility poles, lightposts and buildings. Those opposed to the new technology claim it violates their privacy since they believe it’s equivalent to having microphones throughout the community. Supporters, however, believe it’s a great way to help reduce gun violence.

ShotSpotter: Reveals Critical Data not Available Elsewhere

Jennifer Doleac, an assistant professor of public policy at the University of Virginia, who studies the connection between gunfire and crime, and Purdue University professor Jillian Carr used ShotSpotter to help determine how Washington, D.C.’s juvenile curfew affected gun violence. The D.C. curfew switches from midnight to 11 p.m. on September 1st every year. If curfews reduce gun violence, the number of incidents from 11 p.m. to midnight should go down. The researchers installed the devices throughout Washington, D.C. neighborhoods and then waited – seven years – to analyze the results. They found that the city's juvenile curfew actually increased the number of gunfire incidents by 150 percent during the 11 p.m. hour.

Doleac, Carr and other researchers found that the data produced by ShotSpotter did not provide a full explanation of why shots were fired or who was firing them. But, this data was an important factor in painting the complete picture, that juvenile curfew policies were counterproductive. More data like this is needed to effectively study gun violence.

Hillard Heintze Blog