False Alerts Related to GPS Electronic Monitoring in Illinois Cook County Sheriff's Office

Abstract

The number of people under electronic monitoring has grown due to the increased use of Global Positioning System (GPS) technology. Meanwhile, a rise in false alerts (i.e., violation alerts that turned out to be groundless) from monitoring devices has concerned many as it has strained resources and disrupted lives. Analyzing Illinois Cook County Sheriff's Office electronic monitoring data, we examined whether false alerts increased following the transition to GPS, how false alerts from GPS monitoring were spatially distributed, and to what extent false alerts were associated with GPS drift (position errors). The rate of monthly false alerts increased from 57.79% in 2017–2019 (radio frequency) to 95.50% in 2021–2023 (GPS). Zip codes with high rates of false alerts have tall buildings that are known to cause GPS drift. Analyzing GPS locations of monitored participants in Geographic Information Systems, we found that false inclusion zone violation alert incidents are closely linked to GPS drift. Results indicate that limitations of GPS technology are inadequately addressed in the current arrangement of electronic monitoring involving law enforcement personnel, and private contractors. Sociotechnical reliability should be improved for electronic monitoring to be utilized as a genuinely cost effective and less restrictive alternative to incarceration.