Is ShotSpotter Effective? Gunshot-detection technology can help police departments if they use it properly.

Facial recognition. Drones. Police have adopted a range of new technologies in recent years to help prevent and respond to crime.

Yet some of the most intense controversies still swirl around a product that’s been around for decades: gunshot-detection technology (GDT), most prominently ShotSpotter, which now operates in roughly 170 cities.

ShotSpotter uses an array of acoustic sensors to listen for loud noises, identify those likely to be gunfire, and alert law enforcement. Despite the system’s straightforward premise, several cities—most notably Chicago—have discontinued its use, citing concerns about effectiveness and racial disparities.