The collection and tracking of crime data based on geography has been a common police practice for decades. Historically, wall charts containing pushpins or other symbols denoted the locations of specific crimes; more recently, computer-mapping programs have assumed similar functions. Whether manual or automated, the traditional ‘pin map’ technique does little to assist police with the interpretation and analysis of law enforcement data. This critical shortcoming led the Illinois Criminal Justice Information Authority to develop the Spatial and Temporal Analysis of Crime (STAC) program.
STAC provides law enforcement agencies with the capacity to identify clusters of criminal activity in their communities. STAC consists of two programs designed to run on a personal computer: the Time Analyzer and the Space Program. The Time Analyzer identifies the most likely time of day and day of week that a particular type of crime will occur. The Space Program identifies those areas in a community containing the greatest concentrations of crime—so-called Hot Spot Areas. Together, these two programs can provide law enforcement officers with the information they need to make both tactical and strategic decisions for solving and preventing crime.
The latest application of STAC—the Automated Early Warning System—builds on the automated Hot Spot Area search and other tools of the basic program. The Early Warning System is based on a sophisticated statistical model that consolidates spatial information from a variety of sources, including law enforcement, public health, housing, economic development and other disciplines. The Early Warning System is designed to identify neighborhoods at high risk of experiencing an outbreak of serious gang-related violence and homicide. By identifying these high-risk areas before a serious outbreak of crime actually occurs, law enforcement and community agencies can more effectively target and carry out intervention and prevention efforts. The Early Warning System is currently being developed as a prototype application for one high-crime area on Chicago's West Side (Area 4). Like the basic STAC program, however, the Early Warning System has potential applications in other neighborhoods of Chicago and in other law enforcement agencies throughout Illinois and the nation.
The single most important achievement to date with STAC has been the development, testing, and refinement of the Hot Spot Area search capability. For the first time, law enforcement agencies can analyze the scatter of events across a map, and then delineate, without regard to artificial boundaries such as zip codes or police districts, the areas of the map that contain the densest clusters of events. Armed with this information, law enforcement can now develop patrol, intervention, and prevention strategies that more precisely address the problems of their neighborhoods.