The purpose of the study was to investigate the role and impact of forensic science evidence on the criminal justice process. The study utilized a prospective analysis of official record data that followed criminal cases in five jurisdictions (Los Angeles County, California; Indianapolis, Indiana; Evansville, Indiana; Fort Wayne, Indiana; and South Bend, Indiana) from the time of police incident report to final criminal disposition. The data were based on a random sample of the population of reported crime incidents between 2003 and 2006, stratified by crime type and jurisdiction. A total of 4,205 cases were sampled including 859 aggravated assaults, 1,263 burglaries, 400 homicides, 602 rapes, and 1,081 robberies. Descriptive and impact data were collected from three sources: police incident and investigation reports, crime lab reports, and prosecutor case files. The data contain a total of 175 variables including site, crime type, forensic variables, criminal offense variables, and crime dispositions variables.