The purpose of this data collection was to investigate the effects of changes in police evidence procedures and the effects of providing feedback to officers on felony case charge reductions or dismissals due to evidentiary problems. The data were designed to permit an experimental assessment of the effectiveness of two police evidence collection programs implemented on April 1, 1985. One of these was an investigative and post-arrest procedural guide. The other was an individualized feedback report prepared by prosecutors for police officers. The officer file includes information on each officer's sex and race, length of police service, and assignment changes during the study period. Data on the offender and the case files include time of arrest, information on arresting officer, original investigating officer and principal investigating officer, offense and victim characteristics, arrestee characteristics, available evidence, case processing information, and arrestee's criminal history.