Gunshot Detection

Tracking & Analytics

Approach

Acoustic gunshot detection systems, which have been adopted by more than 90 US jurisdictions,1Jillian B. Carr and Jennifer L. Doleac, “The Geography, Incidence, and Underreporting of Gun Violence: New Evidence Using ShotSpotter Data,” The Brookings Institution, April  2016, 4-5, https://brook.gs/2J7zgej. have the goal of accurately detecting and locating gunfire in order to improve police response to gunshot incidents.2Kyung-Shick Choi, Mitch Librett, and Taylor J. Collins, “An Empirical Evaluation: Gunshot Detection System and its Effectiveness on Police Practices,” Police Practice and Research 15, no.1 (2014): 48-61; Dennis Mares and Emily A. Blackburn, “Evaluating the Effectiveness of an Acoustic Gunshot Location System in St. Louis, MO,” Policing 6, no. 1 (January 27, 2012): 26-42. With this technology, sensors that can detect acoustic soundwaves produced by gunfire are placed strategically throughout a targeted area.3Michael Litch and George A. Orrison, IV, “Draft Technical Report for SECURES Demonstration in Hampton and Newport News, Virginia,” (unpublished report, January 2011): 31-34, https://www.ncjrs.gov/pdffiles1/nij/ grants/233342.pdf; Mares and Blackburn, “Evaluating the Effectiveness,” 27-29; Choi, Librett, and Collins, “An Empirical Evaluation,” 51-52. When the sound of gunfire is identified, the location is triangulated, and an alert is sent to local police that includes the location (latitude and longitude) of the incident, the time the incident occurred, and a recording of the incident.Ibid. The entire process takes less than a minute and provides police with highly accurate location information; as a result, gunshot detection systems can help police more quickly respond to gunfire as compared to when it is reported through other methods (e.g., a 911 call).4Ibid. Additionally, these systems can alert police to gunshots that might have otherwise gone unreported.5Ibid.

Impact

Research has shown that properly implemented gunshot detection systems are very effective at accurately detecting and locating gunfire.6Cory Watkins et al., “Technological Approaches to Controlling Random Gunfire–Results of a Gunshot Detection System Field Test,” Policing 25, no.2 (2002): 345; Carr and Doleac, “Geography, Incidence, and Underreporting of Gun Violence,” 4; Litch and Orrison, “Draft Technical Report,” 31-34. Studies have also found that the use of a gunshot detection system can improve police response times to gunshot incidents7Choi, Librett and Collins, “An Empirical Evaluation,” 51-52; Mares and Blackburn, “Evaluating the Effectiveness,” 30-32. and can help alert police to gunfire that otherwise would have gone unreported.8Litch and Orrison, “Draft Technical Report,” 31-34. Gunshot detection systems can also provide police with accurate gunshot data that can be analyzed in order to develop innovative solutions in places with repeated gun violence.9Watkins et al., “Technological Approaches,” 363-66; Andrew Merrill, “The Life of a Gunshot: Space, Sound and the Political Contours of Acoustic Gunshot Detection,” Surveillance and Society 15, no.1 (February 28, 2017): 42-55.

Necessary Resources

To implement a gunshot detection system, law enforcement agencies contract with a company that provides the necessary equipment and training.10Matt Drange, “We’re Spending Millions on This High-Tech System Designed to Reduce Gun Violence. Is It Making A Difference?” Forbes, November 17, 2016, https://www.forbes.com/sites/mattdrange/2016/11/17/shotspotter-struggles-to-prove-impact-as-silicon-valley-answer-to-gun-violence/#d8a8a3e31cb4. The equipment is typically leased rather than purchased, and the agency then pays an annual subscription fee for its use and maintenance.11Ibid. This arrangement can help law enforcement agencies save on upfront costs, but it does allow the provider company to retain ownership of the gunshot data collected.12Ibid. The actual annual costs will depend on the coverage area and how many sensors an agency deploys.13Ibid.

Strategy in Practice

Overview

Gunshot detection systems are also aligned with problem-oriented and predictive policing models, as this technology is typically installed in gun crime hot spots and provides data that can be used to help develop solutions to the problem of gunfire within the community.14Watkins, et al, “Technological Approaches,” 363-66; Mares and Blackburn, “Evaluating the Effectiveness,” 27-29.

Gunshot detection technology is designed to immediately notify first responders in real-time when sensors detect gunfire. Once the acoustic sensor captures perceived gunfire, your public safety agencies may use either audio playback or integration with nearby crime cameras to verify the gunfire incident. If there is evidence of an injury, notifications should trigger an immediate response from your emergency medical personnel to deliver potentially life-saving care and transport injured people to the nearest hospital.

Your local law enforcement agency should deploy nearby patrol officers to investigate the scene of the potential shooting. Responding officers should note and, where appropriate, collect any evidence of a shooting (i.e., bullets, spent cartridges, or damaged property). You should assign the appropriate investigations team to conduct follow up and take over the shooting investigation once the initial scene has been processed.

Common Barriers

False positives: False positives occur when a gunshot detection system is activated by something other than gunfire (e.g., fireworks).15Litch and Orrison, “Draft Technical Report,” 42-44. There is little reliable evidence regarding the rate of false positives;16Carr and Doleac, “Geography, Incidence, and Underreporting of Gun Violence,” 4-5. however, they are among the most common concerns reported by users of gunshot detection systems and can account for a significant portion of activations.17Litch and Orrison, “Draft Technical Report,” 42-44; Ratcliffe et al., “A Partially Randomized Field Experiment.” False positives can create a burden on officers and make them more hesitant to quickly respond when they receive an alert.18Ratcliffe et al., “A Partially Randomized Field Experiment.” Some police agencies have attempted to address this problem by having a staff member manually listen to the recording of the incident to confirm whether it captured gunfire or some other noise.

Limited detection abilities: Though studies have found that gunshot detection systems are overall effective at detecting and locating gunfire, it remains difficult for this technology to detect shots fired indoors or by guns equipped with high-quality suppressors.19Mares and Blackburn, “Evaluating the Effectiveness,” 27-30.

Limited impact on the resolution of gunshot cases: Many evaluations of gunshot detection systems have found that, although the technology can help improve police response times and confer other benefits, the use of these systems rarely leads directly to the arrest or prosecution of a shooter.20Choi, Librett, and Collins, “An Empirical Evaluation,” 58; Mares and Blackburn, “Evaluating the Effectiveness,” 30-32; Drange, “We’re Spending Millions.” Additionally, research is still unclear as to whether gunshot detection systems can actually reduce or prevent shootings.21Ratcliffe et al., “A Partially Randomized Field Experiment”; Litch and Orrison, “Draft Technical Report,” 34-36; Drange, “We’re Spending Millions.”

Agencies, Organizations, and Other Necessary Partners

Gunshot detection system provider: Law enforcement agencies will need to contract with a company to receive the equipment and training to implement a gunshot detection system.

Community partners: Community involvement in the deployment of a gunshot detection system could help increase the technology’s deterrent effect and help strengthen police–community relationships.22Watkins et al., “Technological Approaches,” 366-67.

What Else You Need to Know

Gunshot detection systems can be paired with other technologies to enhance surveillance capabilities and generate more actionable evidence.23Ratcliffe et al., “A Partially Randomized Field Experiment”; Choi, Librett, and Collins, “An Empirical Evaluation,” 58-59. For example, some places electronically tie gunshot detection systems to closed-circuit television (CCTV) cameras so that once a gunshot is detected by the audio sensor, the camera is triggered and pans toward the direction from which the shot originated.Ibid. This can help officers and dispatchers see the location of the gunfire and reduce reliance on eyewitness testimony.24Choi, Librett, and Collins, “An Empirical Evaluation,” 58-59. Gunshot detection systems can also be synced to screens located inside police cruisers25Ibid. and to mobile apps,26David Welsh and Nirmalya Roy, “Smartphone-Based Mobile Gunshot Detection,” Institute of Electrical and Electronics Engineers, 13th Workshop on Context and Activity Modeling and Recognition (2017), https://userpages.umbc.edu/~nroy/courses/shhasp18/papers/p244-welsh.pdf. which makes the technology more flexible and user-friendly for officers.

Newsroom & Resources

  • How ShotSpotter locates gunfire, helps police catch shooters and works to denormalize gun violence (Washington Post, 2017)

  • The geography, incidence, and underreporting of gun violence: new evidence using ShotSpotter data (Carr and Doleac, 2016)