Methodology
More than four years in the making. Over 100,000 pages of government documents. Thousands of record requests and hundreds of interviews. This is what it took to create the largest and most comprehensive database of conditions inside Illinois county jails.
How we collected the records
Our project began in April 2022 when an Illinois Answers Project reporter began filing public records requests for a particular form, the “Report of Extraordinary or Unusual Occurrences,” which jails must file with the state when certain kinds of events happen, such as escapes, riots and fights. The Jail and Detention Standards Unit (JDSU) within the Illinois Department of Corrections (IDOC) receives thousands of these reports from jails each year.
To obtain the records, Illinois Answers negotiated with IDOC, which agreed to provide only the first page of each record, sent in batches grouped by month from 2019 onward. In total, we received more than 30,000 reports.
In order to track jail inspection data, we developed a tool to parse and read more than 24,000 pages of annual inspection reports released by IDOC covering every jail in Illinois going back to 2017. That tool was based on a library initially developed by Jeremy Singer-Vine, currently the data editor at the New York Times. We also read through every report — more than 800 — to find additional details and log them manually.
In order to find cases of people who died in jails but weren’t captured in official state data, reporters requested records from every coroner in the state and reviewed lawsuits, news stories and press releases. Reporters also cross-referenced the “extraordinary or unusual occurrences” dataset and reviewed records from Illinois State Police (ISP) and the Illinois Criminal Justice Information Authority (ICJIA).
How we cleaned and checked them
Illinois Answers partnered with the University of Chicago’s Mansueto Institute for Urban Innovation, where researchers use interdisciplinary methods to tackle complex problems. With their help we developed a pipeline that automatically analyzed our trove of documents using the Open Source Computer Vision Library, Google’s Tesseract optical character recognition engine and Stanford researcher David Lim’s Named Entity Recognition classifier model, which is itself based on Google’s Bidirectional Encoder Representations from Transformers, or BERT, model. A full overview of that method is available on the Mansueto Institute’s GitHub page.
Because the forms were often handwritten, poorly scanned or had missing information, we also visually verified the accuracy of every digitized record using a program we developed in-house that displayed an image of a particular form alongside a data-entry tool.
What the data covers
- 821 jail inspections, 2017–2025.
- 28,963 extraordinary or unusual incident reports, 2019–2025.
- 238 deaths in custody, of which 63 were never counted by the state.
- All 102 Illinois counties. 10 do not operate a jail: Alexander, Brown, Cass, Edwards, Gallatin, Hamilton, Johnson, Pope, Scott, Union.
Who worked on this
This yearslong effort is the result of work of more than a dozen people across several years, including current and former staff members at Illinois Answers, students at the University of Chicago and more than one hundred sources who volunteered their time and expertise.
This database was created by lead data reporter Andrew Adams. Reporters Grace Hauck, Meredith Newman and other members of the Illinois Answers staff contributed data reporting and fact-checking. Ganon Evans and Andres Camacho Baquero of the Mansueto Institute for Urban Innovation built the pipeline that processed “extraordinary or unusual” forms. University of Chicago students Christine Tsai, Eliana Nowlis, Aashni Jain, Maggie Larson and Brock Sauvage fact-checked portions of this database. Kailey Ryan provided illustrations. The project was edited by Jim Daley, Crystal Paul and other members of the Illinois Answers staff. The project is published by the Better Government Association and made possible by grants from the Richard H. Driehaus Foundation, the Alvin H. Baum Family Fund, and support from readers like you.
Read more of our investigation
Building this database was just one part of our look into county jails. In addition to collecting data, we interviewed hundreds of people, combed through thousands of pages of other government documents and coordinated for months with government agencies across the state.
You can read more about our full project’s methodology here.