Crime Lab A Deeper Look at What the Data Tells Us About Electronic Monitoring in Chicago

Amid a historic rise in gun violence, debates about the underlying factors driving the surge in Chicago have grown to include electronic monitoring (EM), a condition of pretrial release that equips people who have been arrested and assigned to EM with a GPS-monitored ankle bracelet while awaiting trial from home instead of jail. However, the lack of easily accessible public data makes it difficult for all sides to agree on the basic facts about EM and its potential effects on public safety. Analysis of the data shared with us by the Cook County Sheriff’s Office (CCSO) and the Chicago Police Department (CPD) allows us to ground the debate about EM in a few essential takeaways: for one, it’s an oversimplification to say that EM is driving gun violence in Chicago, given the timing of the relevant changes in the justice system and the small number of people arrested for gun violence while out on EM compared to overall victimizations.

Nonetheless, the makeup of who is on EM has changed over the past few years: while the largest increase in the use of EM was for gun possession offenses, the number of people on EM for a homicide or shooting is also much higher than it was in 2016. We also see in the data that people out on EM are themselves victims of violence at a much higher rate than others in the city, suggesting that there’s more to be done to connect people on EM to helpful social services.

In any data analysis, there are numerous details about both the data and analytical methods that can be important for understanding the nuances of what the data can and can’t tell us, as well as reasonable alternative choices about how to analyze the data, interpret and present the results, and address some of the limitations of the data themselves. Because of the space constraints in the article, we have omitted many of those details and sensitivity analyses from the published version. We provide those additional details here.

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EM Data Appendix