Gun Shot Detection

Shotspotter is the largest vendor of audio surveillance systems. It consists of sensors - microphones - distributed over a neighborhood in order to determine the location of a gunshot. Sensor data is then sent through a set of algorithms and analysts to "verify" a gunshot. Verified alerts are then pushed to police in the field. Shotspotter claims to be able to distinguish gunshots from similar sounds such as fireworks and cars backfiring.

Where

Distributed through the Englewood, Harrison, Chicago Lawn and Grand Crossing neighborhoods with approximately 45-60 sensors.

Costs

Shotspotter costs approximately "$100,000 for every 1.5 square miles" of coverage. The Shotspotter deployment in Chicago was funded primarily through money seized through the war on drugs. In addition to the devices, analysts, algorithms and software licenses, there are additional costs due to police responding to false alarms from fireworks, cars, and other ambient noise.

Capabilities

Vendors claim these devices are able to detect gun shots and reduce shootings. They operate by distributing sensors over a broad area, and using the sound wave and time of arrival at each sensor for detecting gunshots and localizing the position of the gunshot.

Efficacy

The efficacy of the devices in Chicago is currently unknown. There are reports of many false positives reported by the Shotspotter system. Under testimony, Shotspotter representatives stated their accuracy numbers were "invented by the company’s sales and marketing team" according to the San Francisco Examiner. Records from the San Diego Police Department place the false positive rates, when police respond to a call of a shooting when there isn't one, at around twelve percent. The efficacy of Shotspotter is also in question due to potentially altered court testimony from the company. The sharp rise in shootings between 2016 and 2020 raise questions about the ability of these systems to detect, respond to, and ultimately prevent crime.

Legal and Privacy Concerns

Shotspotter is marketing its technology for several new markets, including in schools as an early detection and response to school shootings. However, the increasing use of this technology in areas where people will be speaking raises concerns with how the data is handled and stored, as the Shotspotter microphones can pick up conversations, thereby becoming a remote wiretapping system.