4 Takeaways: AP investigates gunshot detection technology

By GARANCE BURKE, MARTHA MENDOZA, JULIET LINDERMAN and MICHAEL TARM
Associated Press

Michael Williams, a 65-year-old grandfather from Chicago, sat behind bars for nearly a year accused of murder. But the key evidence against Williams didn’t come from an eyewitness or an informant; a major factor was a loud bang picked up by a network of surveillance microphones. Prosecutors said technology powered by a secret algorithm that analyzed noises detected by the sensors showed Williams shot and killed the man. Last month, a judge dismissed the case against him at the request of prosecutors, who said they had insufficient evidence. Williams’ experience highlights the real-world impacts of society’s growing reliance on algorithms to help make decisions that have significant impacts on public life.