Sounds of fury
To help combat rampant gang violence in South Los Angeles, Calif., the Los Angeles County Sheriff’s Department has installed a wide-area acoustic surveillance system to locate gun violence as it happens and to help the department develop strategies for reducing it. The technology also has proved useful in prosecuting criminals.
Los Angeles County deployed the ShotSpotter Gunshot Location System (GLS) in 2006, covering 1.5 square miles. The system consists of 20 wide-area acoustic sensors mounted covertly on rooftops and other secure access locations, a central server and a user interface program called the Public Safety Console (PSC). When several sensors pick up a loud, impulsive sound, the system classifies the sound as a gunshot or other acoustic event (fireworks, etc.) and determines its exact location using acoustic triangulation. The location is displayed on a satellite map by the PSC, which resides on a computer in police command or the dispatch center.
The PSC alerts the dispatcher when a gunshot is detected and displays the alert and incident intelligence with the map. Dispatchers can listen to audio clips of the gunshot and review historical map data to analyze the incident. The GLS detects gunfire activity 24 hours a day and permanently stores all incident information in an auditable, verifiable database repository located at the company’s headquarters.
Last year, the Los Angeles District Attorney’s Office and the Los Angeles County Sheriff’s Department used the technology to successfully prosecute two gang members for the murder of a rival. The system identified and alerted deputies to the crime location, so they could recover evidence, including shell casings that confirmed the types of weapons involved in the shooting.
In prosecuting the case, the county used a forensic analysis of the event that the company provided to help corroborate witness testimony that more than one shooter was involved. The analysis established that weapons of two different calibers had fired a total of 18 rounds during the incident. A timeline of shots fired was constructed that showed that two weapons were involved and which gun had fired which round. An audio recording of the event, automatically captured by the surveillance system, also was played for the court. “[The] combination of technology and data analysis, in my opinion, was crucial to convince the jury,” says Los Angeles Detective Ty Labbe.
Project: Gunshot location detection system
Jurisdiction: Los Angeles County
Agency: District Attorney’s Office, Sheriff’s Department
Vendor: Mountain View, Calif.-based ShotSpotter
Date installed: 2006