After describing the monitoring study's design, the report examines the effects of tape recording on police practices and procedures. Interviews in taped cases tended to be shorter than in untaped ones, and tape recording appeared to save time in report writing. In two sites, the taped cases obtained significantly more confessions than untaped cases. In assessing the effects of taping on police interview style and intelligence gathered, the report concluded that better information was collected with less police time invested. The report describes the average length of time taken by prosecutors to review taped cases and examines change in plea rates, lengths of hearings at both lower and high courts, and frequency of challenges to police interview evidence at court. Tables and approximately 50 references.