Questioning is viewed as the point of departure for all criminal investigations. As an everyday police activity, interrogation requires a basic understanding of human psychology. The textbook presents an introduction to the meaning and principles of interrogation in criminal matters; human rights criteria and procedures to be observed in interrogation, as well as potential problems and abuses in borderline cases. Various levels of interrogation, e.g., police investigations, preliminary court proceedings, and questioning in trials are discussed. Also considered are the psychological training desirable for interrogation; the psychology of the accused and his defense strategies, as well as procedures for dealing with the problems and the phenomenon of confession, false and withdrawn confessions, and methods of testing the validity of confessions. Further topics of discussion are determination of personal and environmentally induced motives; lying and other psychopathological forms of expression; the psychology of witnesses, including witness types, kinds of statements, psychological bases for statements, and problems in testing the veracity of children's statements. Methods and problems in keeping written interrogation records during preliminary and main proceedings are reviewed. Separate notes for each chapter and an extensive bibliography are provided. --in German.