CHICAGO—Only 9 percent of ShotSpotter alerts responded to by Chicago police officers led to evidence of gun crimes, according to an August report by the City of Chicago’s Office of Inspector General (OIG). The ShotSpotter system, developed by a California-based company named ShotSpotter, uses acoustic sensors to detect gunshots in real-time for faster and more precise police responses. Including New York, San Francisco, and Minneapolis, 119 U.S. cities use the system. Chicago—ShotSpotter’s largest customer—uses the system in 12 police districts covering over 100 square miles, mostly on the crime-infested South and West Side. After the ShotSpotter system detects likely gunshots, the sound waves are sent to a human acoustic expert at ShotSpotter headquarters. After the expert’s approval, the City of Chicago Office of Emergency Management and Communications will be notified to dispatch police officers to the scenes. Between Jan. 1, 2020, and May 31, 2021, Chicago police officers responded to 50,176 …