Space-Time Association between Gunshot Detection Alerts, Calls for Service, and Police Enforcement in Chicago: Differences Across Citizen Race and Incident Type

Eric L. Piza, George O. Mohler, Nathan T. Connealy, Rachael A. Arietti, and, Jeremy G. Carter (2024)

Journal of Quantitative Criminology

Key Takeaways

• The study investigates the association between Gunshot Detection Technology (GDT) alerts, calls for service (CFS), and police enforcement actions in Chicago
• Results indicate significant spatial and temporal associations between both GDT alerts and CFS with subsequent arrests and stops
• The effect of GDT and CFS was largely consistent across different racial groups, with no clear patterns of racial disparity emerging specifically due to GDT
• The results suggest that any racial disparities in enforcement are more likely related to broader police response processes rather than the use of GDT itself

Research Summary

Chicago Mayor Brandon Johnson partially campaigned on a promise to terminate the City’s Gunshot Detection Technology (GDT) contract, arguing the system was unreliable, overly susceptible to human error, and played a pivotal role in the police killing of 13-year-old Adam Toledo. Johnson delivered on his promise on February 13, 2024 by announcing his decision to discontinue the use of GDT, with a phasing out of the technology set to begin during September 2024.

Recent research found that Chicago’s GDT system did not impact levels of gun violence or increase closure of shooting incidents in GDT-covered police districts. However, the level to which GDT contributed to the over-policing of people of color in Chicago remains an open empirical question.

Critics argue that GDT disproportionately targets disenfranchised communities, while supporters purport that GDT coverage areas reflect gun violence levels. Descriptive statistics in Chicago lend credence to both perspectives. Per capita gun crime levels were upwards of 1.5 times higher in the GDT target area than the remainder of the city, with the non-white population and poverty rate over twice as high and ~ 50% higher, respectively. An important question is whether the context of GDT deployment translates into enhanced enforcement, specifically against people of color.

This study directly examines whether GDT leads to increased arrests and stops compared to traditional calls for service (CFS) and whether these enforcement actions exhibit racial disparities. The researchers employed the Knox test and point process test to analyze the spatial and temporal clustering of GDT alerts and CFS with subsequent arrests and stops. The analysis was conducted using data provided by the Chicago Police Department. The study disaggregates arrests and stops by type (gun, drug, traffic for arrests; suspect, traffic, investigative, gang, victim, or other for stops) and by race/ethnicity to identify any disproportionate effects across different racial groups.

The findings indicate a significant association between GDT alerts and increased arrests and stops in close spatial and temporal proximity. This association was also observed with traditional CFS, suggesting that GDT alerts are not uniquely driving police enforcement activities. The analysis revealed that the relative effect of GDT and CFS on enforcement actions was consistent across racial groups in most instances. However, there were a few instances of disparate effects. For some racial groups and specific types of arrests or stops, GDT was associated with heightened enforcement, while for others, CFS had a more pronounced effect. However, these effects did not consistently favor one racial group over another, suggesting that GDT itself does not exacerbate racial disparities beyond existing levels.

Overall, the study concludes that Chicago’s GDT system did not create additional racial disparities in arrests and stops beyond those already present in standard police responses to gunfire. The observed disparities in enforcement are more likely attributable to the general processes of reporting and dispatching incidents rather than the specific use of GDT. The authors suggest that the implementation of GDT should be considered in the context of its overall effectiveness and potential to improve police response times and spatial accuracy without disproportionately impacting any specific racial group.