A GIS is an automated database that stores, analyzes, and displays both spatial and nonspatial data. GIS's use digital data to create layers of information that are stacked in the computer on top of one another like transparent overlays. When the various layers of information, both spatial and nonspatial, are combined in this manner, a synergistic effect occurs. The result is a powerful analytical tool with criminal justice applications. Two obvious criminal justice applications of GIS's are facility siting and crime fighting. Political considerations have often dominated the site selection process in the past and will likely continue to do so; however, their influence could be tempered by the judicious use of a GIS. If, after consultation with experts in the field, essential factors are agreed upon in advance in open public meetings by all parties concerned, a GIS could then be used to draw up an impartial list of all sites in the State that meet those agreed upon basic criteria. From this list of qualified sites, the final selection could then be made, using whatever additional criteria the politicians insist upon. A number of police departments have installed GIS's of their own and used them for routine functions, such as producing beat maps, planning patrol strategies, and maximizing efficiency in the serving of warrants. Additionally, a growing number of scholars have noted that when GIS is used in conjunction with enhanced 911 and computer-assisted dispatch, law enforcement officials can gain a much better understanding of the nature and magnitude of their crime problems. Many criminal justice agencies are unwilling or unable to set up their own individual GIS's; however, they could "piggyback" onto already existing GIS systems and take an active role in the planning of future ones. 32 references