The text examines individual motivation and perception and describes how law enforcement can benefit from using psychological insight when dealing with offenders, victims, eyewitnesses, and juries. Social scientists have become increasingly interested in crime as an interacting system in which the victim, the offender, and society play complex roles. Pioneer collaborations between police and social scientists, based in part on this 'new' theory, have occurred to resolve domestic disputes and hostage situations and structure police personnel management. Their interaction is also evident in the areas of eyewitness testimony, lineups, and the use of the psychological researchers as courtroom experts. For example, the social scientist understands that eyewitness testimony is based, in effect, on one person's theory about a past reality. Because that theory can be adjusted or changed according to the personality, the situation, or social pressure, the psychologist must argue against accepting such testimony without question. Social scientists, through their examination of simulated jury processes, must also raise questions about the impact of changes in the jury system on both individual verdicts and on the delivery of justice. Knowledge gained through social science research can help resolve such critical issues as the role of capital punishment and of prisons in modern society. In addition to amplifying psychology's role in criminal justice, the text reviews social science research methods and presents a published mock jury study with interpolated notes for 'consumers' and aspiring researchers. Also, a law and social sciences research file contains related documents and sample questionnaires and criminal justice educational material. An extensive bibliography of about 400 references, case citations, tables, photographs, glossaries of criminal justice and psychology terms, and name and subject indexes are provided.