The first paper examines ethical dilemmas facing investigators in such areas as entrapment, interrogation, courtroom deception, and narcotics law enforcement. Remedies to these dilemmas also are suggested. The second paper traces the historical development of crime pattern analysis, describes crime analysis functions, and illustrates the operation of three crime pattern analysis units. The third paper discusses descriptive, explanatory, and predictive methods of scientifc inquiry, examines the traditional investigative role, and argues for the utility of the predictive method in police investigations. The next paper examines the motives and motivations of the police informant and the elements of informal (traditional) and formal strategies for the management of confidential informants. Within the context of the Mincey v. Arizona decision, the fifth paper considers crime scene warrant requirements and voluntariness requirements in police interrogations. The next selection examines difficulties in interpreting evidence obtained through electronic surveillance and suggests the need for a reevaluation of the costs and benefits of this investigative technique. The seventh paper examines the incidence and characteristics of autoerotic deaths in Illinois and provides guidelines for differentiating such accidental deaths from suicides. The final contribution presents the findings of a study of judges' perceptions of police testimony and the impact of officers' courtroom preparation, appearance, and attitudes on their credibility as witnesses. Each selection provides notes and references. An index is included.