NCJ Number
80938
Date Published
1981
Length
71 pages
Annotation
This report discusses problems inherent in the use of aggregate data to estimate the flow of individuals and cases through the Illinois criminal justice system and outlines a method for accurately estimating the flow from the police system to the court and correctional systems.
Abstract
It is not possible to measure directly the movement of cases through individual components of the criminal justice system, but it is possible to estimate this flow by using available aggregate data. However, many pitfalls exist in using such information, and any one of many common errors can invalidate the entire analysis. This report first examines major difficulties in system flow analysis, including varying definitions of crimes and units of comparison among organizations and the collection of separate statistics for adult and juvenile offenders. Attention is then focused on the specific problems caused by the Illinois police aggregating their data into nine categories of Index crime while courts and correctional agencies aggregate their data into felonies and misdemeanors with six categories of felonies. Some Index crimes are not felonies, and some Illinois felonies are not Index crimes. In addition, no single Index crime category is comparable to any single felony category. Following an example of an invalid system flow analysis that compares Part I crimes to felonies, this report suggests a solution. Since 1972, the Department of Law Enforcement (DLE) has collected and maintained a police data set categorized into 227 types of crime, most of which correspond to a unique statutory class of felony, misdemeanor, and petty or business offenses. This makes it possible to aggregate police data by statutory class and produce a classification system that is comparable to those used by court and correctional agencies. This system is applied to the same data used in the invalid example to produce a valid system flow analysis. Drawbacks of this model are discussed, as are special problems posed by data in Chicago and Cook County. Guidelines for analyzing aggregate data conclude the report. The appendixes contain a classification of offenses in Illinois law and materials on the DLE crime categories and their correspondence with statutory classes. Tables and seven references are included.