ALTHOUGH THE PRESENT EDITION CONTINUES TO FOCUS ON OPERATIONAL EFFECTIVENESS IN THE ESSENTIAL MISSIONS OF INVESTIGATIVE WORK, IT HAS MAINTAINED ITS EMPHASIS ON THE OBSERVANCE OF THE RIGHTS OF THE SUSPECT AND THE ACCUSED. THROUGHOUT THE TEXT A THEORY OF INVESTIGATION IS DEVELOPED. A STATEMENT OF PRINCIPLES IN THE EARLY CHAPTERS IS RELATED TO THE INVESTIGATIVE PROCEDURES DESCRIBED IN THE LATER PARTS OF THE BOOK. THE CONCEPTS OF 'INFORMATION' AND 'INSTRUMENTATION' HAVE BEEN BROADENED TO INCLUDE A DISCUSSION OF FEDERAL DATA BANKS AND THE APPLICATIONS OF COMPUTERS TO INVESTIGATIVE PROBLEMS. A STUDY GUIDE FOR THIS TEXT HAS ALSO BEEN PUBLISHED (NCJ-13374). (AUTHOR ABSTRACT)