{"id":"AIBD-1201","title":"An NIJ-funded evaluation finds that ShotSpotter alerts brought Kansas City and Chicago police to gunfire sooner, with no gain in crime control","summary":"In an NIJ-funded evaluation, Kansas City officers reached ShotSpotter alerts in 266.82 s against 390.87 s for citizen calls, and NIBIN evidence collection rose 30.4%. Crime did not fall.","date_observed":"2024-01-01","date_basis":"source publication","date_precision":"month","benefit_status":"mixed","source_collection":null,"source_entry":null,"account":"ShotSpotter, now SoundThinking, sells gunshot detection with acoustic sensors and a machine-learning classifier, and its Incident Review Center staff confirm each alert. Kansas City installed it over about 3.5 square miles in October 2012, and Chicago reached about 100 square miles by May 2018. Eric Piza's team at Northeastern University evaluated both deployments for the National Institute of Justice in a report received in January 2024. The team compared locator data for alerts and citizen calls, built synthetic control areas and matched incidents with and without coverage. In Kansas City, officers reached shots-fired alerts in 266.82 s against 390.87 s for calls and stopped 35.66 m from the gunfire against 54.62 m. NIBIN evidence collection was 30.4% higher in the covered area than in its control. In Chicago, firearms were 45% more likely to be recovered from fatal shootings in covered areas. Shootings did not fall in either city, Chicago's covered areas saw more shootings than their controls and case clearance did not improve. The authors write that the procedural benefits did not translate to any meaningful improvements to crime control outcomes.","category":"aggregate result","unexpected":false,"purpose":"ShotSpotter built its gunshot detection system to detect and locate outdoor gunfire with acoustic sensors and send police an alert for each confirmed incident.","system":"ShotSpotter gunshot detection technology (GDT), with alerts confirmed at the Real-Time Incident Review Center","model_version":null,"developer":"ShotSpotter, Inc. (renamed SoundThinking, Inc. in 2023)","deployer":"Kansas City Police Department and Chicago Police Department","location":"Kansas City, Missouri and Chicago, Illinois, United States","domain":"Policing (gunfire detection)","segment":null,"benefit_type":"Reduced Task Time","work_activities":["4.A.1.b.1","4.A.1.a.2"],"taxonomy_note":"The gains found are sooner and closer arrival and more evidence collected, with no reduction in shootings.","registry_ids":{},"ratings":[{"group":"organizational","depth":2,"reason":"Kansas City officers reached shots-fired alerts about two minutes sooner than citizen calls and stopped closer to the gunfire, and NIBIN evidence collection was 30.4% higher in the covered area."},{"group":"societal","depth":null,"reason":"Shootings and case clearance did not improve in either city, so no gain for residents is established."}],"ai_role":{"status":"assessed","statement":"The evaluation compared responses to alerts with responses to citizen calls and compared covered areas and incidents with weighted controls, so it isolates the system's part in the procedural gains. The system includes acoustic experts who confirm each alert, and the report does not separate the classifier from the reviewers."},"evidence":[{"kind":"evaluation report","citation":"Piza, Eric L., George O. Mohler, Jeremy G. Carter, David N. Hatten, Nathan T. Connealy, Rachael Arietti, Jisoo Cho and Emily Castillo. The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Evaluation. Final report to the National Institute of Justice, award 2019-R2-CX-0004, document 308357, January 2024.","title":"The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Evaluation","url":"https://www.ojp.gov/pdffiles1/nij/grants/308357.pdf","date":"2024-01-01","written_by":"independent","quote":"GDT seems to positively impact a number of procedural aspects of police response to gun fire. GDT further demonstrates a positive influence on evidence collection. Unfortunately, these procedural benefits did not translate to any meaningful improvements to crime control outcomes."},{"kind":"evaluation report","citation":"Piza, Eric L., George O. Mohler, Jeremy G. Carter, David N. Hatten, Nathan T. Connealy, Rachael Arietti, Jisoo Cho and Emily Castillo. The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Evaluation. Final report to the National Institute of Justice, award 2019-R2-CX-0004, document 308357, January 2024.","title":"The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Evaluation","url":"https://www.ojp.gov/pdffiles1/nij/grants/308357.pdf","date":"2024-01-01","written_by":"independent","quote":"NIBIN evidence collection was 30.4% higher in the GDT target area than the weighted control area."},{"kind":"evaluation report","citation":"Piza, Eric L., George O. Mohler, Jeremy G. Carter, David N. Hatten, Nathan T. Connealy, Rachael Arietti, Jisoo Cho and Emily Castillo. The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Evaluation. Final report to the National Institute of Justice, award 2019-R2-CX-0004, document 308357, January 2024.","title":"The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Evaluation","url":"https://www.ojp.gov/pdffiles1/nij/grants/308357.pdf","date":"2024-01-01","written_by":"independent","quote":"Firearms were 45% more likely to be recovered from fatal shooting incidents occurring within the GDT target area as compared to the control area."},{"kind":"other","citation":"SoundThinking. ShotSpotter Gunshot Detection System, product page.","title":"ShotSpotter Gunshot Detection System","url":"https://www.soundthinking.com/law-enforcement/gunshot-detection-technology/","date":null,"written_by":"makers","quote":"If an incident is created and sent to our Incident Review Center the short audio snippet is stored permanently for evidentiary purposes as well as to train the machine learning model.","supports_benefit":false}],"replication":{"produced_by":["Acoustic sensors covered about 3.5 square miles of Kansas City from October 2012 and about 100 square miles of Chicago by May 2018.","ShotSpotter's acoustic experts reviewed each detection before an alert went to police.","Officers were dispatched to alerts as they were to citizen calls, and patrol-car locator data recorded their movements."],"must_hold":["Sensors must cover the area where the gunfire occurs.","Police must dispatch officers to the alerts and collect evidence at the scene."],"echoes":[]},"paired_incident":null,"headline":"*ShotSpotter* got police to gunfire sooner, but crime did not fall","metric":"266.82 s against 390.87 s","comparator":{"against":"Citizen calls for service about shots fired in Kansas City","before":"390.87 s to arrive on scene, stopping 54.62 m from the gunfire","after":"266.82 s to arrive on scene, stopping 35.66 m from the gunfire","basis":"measured","quote":"Officers arrived on the scene quicker when responding to GDT alerts than CFS for shots fired incidents (266.82 s vs. 390.87 s) and fatal shootings (140.44 s vs. 417.80 s), and took longer to arrive on scene for non-fatal shootings (428.20 s vs. 383.19 s).","url":"https://www.ojp.gov/pdffiles1/nij/grants/308357.pdf"},"later":null,"learns_from_data":{"value":"shown","note":"SoundThinking's product page says that audio from reviewed incidents is kept to train the machine learning model that filters detections. 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