Short-Term Trends in Jail Bookings & Populations After the Pretrial Fairness Act

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    David Olson & Don Stemen ·


On September 18, 2023, Illinois’ Pretrial Fairness Act (PFA) took effect. The PFA not only eliminated the use of cash bail as a condition of pretrial release in Illinois, but also imposed limits on the use of pretrial jail detention. Based on interviews with criminal justice practitioners and stakeholders, there were mixed expectations about would happen to pretrial jail populations after implementation of the PFA. Some predicted that pretrial jail bookings and pretrial populations would fall. Others believed there would be no change in bookings or populations, but a change in the composition of those held – specifically, an increase in the proportion of people held on more serious criminal charges. Still others believed that jail populations would increase, as defendants who previously would have been released quickly after posting bond under the old law would now be held in detention until their cases were disposed under the new law.

As part of our long-term evaluation of the implementation and impact of the PFA, this interim research brief examines whether pretrial bookings and the size of pretrial jail populations changed across Illinois during the first few months after implementation of the law. We found that jail bookings and average populations deceased during the first three months of the PFA more than would have been expected based on historic trends, and the magnitude of these decreases varied across different regions of Illinois. The data used for these analyses are reported to the Illinois Department of Corrections’ (IDOC) Jail and Detention Standards Unit (JDSU) by each county Sheriff in Illinois. Loyola’s Center for Criminal Justice collaborated with IDOC’s JDSU to enter these data, perform some data quality review, and create a data dashboard that allows the public to examine trends and patterns in jail use across Illinois.

Understanding Patterns in How Jails Are Used in Illinois

A jail booking is defined as an individual being admitted to the jail. Most jails in Illinois serve as central booking facilities for their counties, meaning all arrested individuals are fingerprinted and have arrest forms completed in county jails. Individuals can be booked into jails but can spend relatively little time in custody if they are simply fingerprinted, identified and released. Individuals also are often held in jail if they are required to have a bond hearing (prior to the PFA) or a hearing to determine detention or conditions of release (under the PFA), which may lead to a longer time in custody. Average daily populations (ADP) of jails, on the other hand, measure how many people were detained in the jail on any given day and tend to be more representative of people who spend longer periods of time in custody.

Before examining whether pretrial jail bookings and pretrial ADPs changed in the three months following the implementation of the PFA, it is important to note historic trends and patterns in these measures of jail use. Just as crime and arrests are generally higher in summer months and lower in winter months, jail bookings and ADPs also show seasonal fluctuations, generally decreasing from summer to winter simply because of this seasonal decrease in crime and arrests. Thus, because the PFA was implemented in the middle of September, we may expect some regular, seasonal decreases in jail bookings and populations after implementation. To provide an initial examination of the potential impact of the PFA on bookings and jail populations, we looked at average changes from summer months (June, July, August) to fall months (October, November, December) in prior years and compared that to changes in 2023.

During 2023, there were 91 county jails operating in Illinois across the state’s 102 counties.

Statewide, and across most individual counties, there were annual decreases in pretrial jail bookings and pretrial populations from summer to fall. In 2022, for example, pretrial bookings statewide fell 14% from the summer period compared to the fall period (Figure 1). In Cook County, these pretrial bookings fell 17% in 2022, while in counties outside of Cook County, the combined pretrial bookings decreased 13% in 2022. Historically, from 2014 through 2022, the percent decrease in pretrial bookings from summer to fall averaged 11.5% (Figure 1). While the decline was much smaller, during the period from 2014 through 2022 the combined pretrial jail ADPs in Illinois also fell from summer to fall, by an average of 3% (Figure 1). Finally, most jail admissions and collective days spent in custody are for individuals in a pre-trial status. Statewide in 2022, 89% of all jail admissions and 91% of all jail-bed days were for individuals held pretrial. This pattern—most admissions and jail-bed days accounted for by individuals held pretrial--was evident across almost every county jail in Illinois during 2022.

Pretrial Jail Bookings Pre- and Post-PFA

To determine the extent to which changes in pretrial jail bookings and average daily pretrial jail populations could be attributed to the PFA, two different sets of analyses were performed. First, the historic (2014 to 2022) changes in the number of pretrial bookings and average daily pretrial jail populations from summer to fall were examined. These analyses were done statewide, as well as across different regions/types of counties, including Cook County, urban counties outside of Cook County, and rural counties. Second, bookings and population figures for the period from October to December 2023 were compared to the June to August 2023 period, to determine if the changes seen were larger than what had historically occurred. As with bookings, these analyses of average daily pretrial jail populations also examined statewide patterns as well as those across different regions/county types.

Statewide, pretrial jail bookings fell 17.5% between summer 2023 (i.e., pre-PFA) and fall 2023 (i.e., post-PFA); based on historical patterns, we would have expected them to fall roughly 11.5% during this period. Thus, pretrial jail bookings fell 6 percentage points more after the PFA than we would have expected (Figure 2), which translates to roughly 3,000 fewer people admitted to jails statewide in the three months from October to December 2023.

These decreases were evident across different types of counties: the decrease in Cook County was 3 percentage points larger than would have been expected; other urban jails experienced a decrease that was 6 percentage points larger than expected; Illinois’ rural jails collectively saw a decrease that was 8 percentage points larger than expected (Figure 2).

Pretrial Jail Average Daily Populations (ADPs) Pre- and Post-PFA

A more substantial decrease potentially attributable to the PFA was evident when changes in the pretrial jail ADPs were examined. Statewide, pretrial jail ADPs in Illinois fell 14% from summer 2023 (i.e., pre-PFA) to fall 2023 (i.e., post-PFA); historically, we would have expected them to only fall an average of 3% during this period.

Thus, pretrial jail populations fell 11 percentage points more after the PFA than we would have expected (Figure 3). Based on these patterns, it is estimated
that the pretrial jail ADP across all counties in Illinois combined decreased by roughly 1,500 individuals due to the PFA. In other words, it is estimated that the statewide pretrial jail ADP in Illinois was roughly 12,200 in the fall of 2023 but would have been roughly 13,700 without the PFA.

As with pretrial jail bookings, the decrease in pretrial jail populations after the PFA was larger in some jails than others. In Cook County, the jail population fell 10 percentage points more than would have been expected, compared to a decrease of 13 percentage points more than expected in other urban counties and a decrease of 15 percentage points more than expected in Illinois’ rural counties (Figure 3).

From interviews and court observations that are part of Loyola’s evaluation, we learned that there is a high degree of variation in pretrial practices across counties post-PFA. For example, in some counties we heard from practitioners that almost all individuals arrested for offenses that are non-detainable under the PFA are not being admitted to the jail; rather, after being fingerprinted and having the arrest paperwork completed, these individuals are released with a court date for their first appearance. Prior to the PFA, most of these same individuals would have been held in jail until either they posted bond or were released on their own recognizance following their first advisement/bond hearing. In contrast, in other counties, it appears that almost all individuals arrested are being held in jail

until they appear before a judge for a conditions or detention hearing within the PFA-mandated 24 to 48 hours. Thus, it is likely that variation across counties in how pretrial jail bookings and ADPs changed after the PFA reflect these differences in how counties have implemented the PFA thus far. Similarly, it is likely that some counties experienced relatively little change in the number of pretrial bookings and jail ADPs after the PFA because they had already been using pretrial detention in a more limited way. Other counties saw more substantial decreases after the PFA because, historically, they had used pretrial detention more broadly, including in cases involving offenses that are not now detainable under the PFA.

Next Steps

In just the three months after the implementation of the PFA, there appears to be evidence that, at least in the short-run, jail bookings have decreased slightly more (by an estimated 3,000) than would normally have been expected (from 50,122 in the three months before the PFA to 41,373, rather than the expected 44,330, in the three months after). The decrease in pretrial jail ADPs has been a bit more substantial, falling an estimated 1,500 more than would historically have been expected (from 14,167 in the three months prior to the PFA to roughly 12,200 in the three months after, rather than the expected 13,700). However, these patterns varied across individual counties and county types. In some counties, the decrease in bookings and pretrial jail ADPs seen after the implementation of the PFA was within what would have been expected given the seasonality of crime, arrests, and pretrial jail admissions, while in other counties it was larger than what would have been normally expected. It is likely that the degree to which pretrial jail bookings and pretrial jail populations changed after the PFA reflects specific local practices and implementation of the PFA.

We will continue examining levels and trends in pretrial jail admissions and populations as the longer-term impact of the changes to pretrial practices take hold, particularly as decisions regarding whether to release those initially held in pretrial detention before the end of the pending criminal case occur. We will also be examining whether the apparent decrease in pretrial jail ADPs has led to increasing numbers of individuals being supervised in the community under pretrial release or electronic monitoring.