The criminal investigation process in municipal and county police departments was studied by survey, interviews and observations, and special data collection. Investigators spend about 7% of their time on activities that lead to solving crimes. Case solutions reflect activities of patrol officers, members of the public, and routine clerical processing more than investigative techniques. Nearly half of investigators' case-related activities are devoted to post-arrest processing; these activities are inadequately responsive to the needs of prosecutors. Collecting physical evidence at crime scenes does not help solve crimes unless evidence processing capabilities are adequate. Policy implications are discussed. (Author).