AP investigates gunshot detection technology

Look at street lights and rooftops in some of America’s poorest neighborhoods today and you might spot what looks like a small box or bowl. These are ShotSpotter recording devices, acoustic sensors paired with algorithms that were developed to detect shots and get the police to the scene faster.

But while the American criminal justice system is outsourcing some of society’s most critical decisions to algorithms and computer code, AP identified a number of serious shortcomings in one of the country’s most popular police technology: Shotspotter’s acoustic shot detection. Prosecutors are increasingly relying on evidence from shotspotters to aid criminal proceedings. But this evidence didn’t hold up in some courtrooms.


This story, supported by the Pulitzer Center for Crisis Reporting, is part of an ongoing series by the Associated Press, Tracked, that examines the power and impact of algorithmic decisions on people’s daily lives.


The central theses:

– The company’s methods of identifying shots are not just guided by technology. ShotSpotter’s staff listen to every possible shot the sensors detect and then either confirm the technology’s conclusion or change the noise source to fireworks, gunshots, or other loud bangs, introducing the possibility of human distortion into the algorithm.

– This gunshot alert tool, which works well to expedite police responses, is increasingly used to create evidence to be touted as definitive evidence in the courtroom that can be used to prosecute and convict defendants. It has been used around 200 times in American courtrooms since 2010, 91 of them in the last four years.

– ShotSpotter claims it helps “save lives, solve cases and deter crime – make communities safer”, but peer-reviewed academic studies state that technology has not reduced gun violence or increased community security in the long term. When urged, CEO Ralph Clark told AP that “ShotSpotter in and of itself cannot prevent or reduce gun violence. What it does is do a very good job of detecting, locating and alerting gunshots in a very reliable way. “

– Defense attorneys oppose ShotSpotter’s claim of science-based evidence. They say the defendants are missing out on their constitutional right to confront all witnesses and evidence because ShotSpotter refuses to divulge its algorithm as its code is a trade secret. As a result, defense lawyers fear that someone could be convicted of a crime they did not commit using ShotSpotter as evidence.