An area of applied psychology traditionally devoted to such problems as testimony, methods of interrogation, and guilt detection.In recent years the field has been expanded, and psychologists serve many other functions: as expert witness in courts; as diagnostician or therapist in correctional institutions; as a student of antisocial behavior; as a consultant in the development of laws; and as a participant in the formulation of legal policies involving human relations. This article will deal with the contributions of psychology in the courtroom, in prisons and training schools, and in the development of laws. The subjects of lie detection, juvenile delinquency, adult crime, and the antisocial personality are discussed under separate topics.Psychology in the Courtroom. The first aspect of the law to be investigated by psychologists was the problem of testimony. At the very beginning of this century a number of noted psychologists including Alfred Binet, Hugo Munsterberg, and Wilhelm Stern conducted research and wrote papers and books on this subject. These and other investigators brought together many experimentally verified findings that are important in the evaluation of testimony—for example, facts on visual illusions, light and dark adaptation, localization of sound, incidental memory, and estimation of size, distance, speed, and time intervals. A specific example is the case of a Canadian hunter who was mistaken for a deer and shot to death by his companions (Sommer, 1959). A psychologist was called in as expert witness and testified on two major points. He pointed out that the mental set, or expectation, of the hunters would tend to make them perceive any moving object as a deer; and he showed that they could not have identified the man by his red coveralls, as the prosecution contended, since the accident occurred late on a cloudy day when the human eye perceives the red end of the spectrum as black (the Purkinje phenomenon).One of Stem’s major contributions was the Aussage (“testimony”) test, which is still used to impress students with the limitations of testimony. One procedure is to have a class or a lecture unexpectedly interrupted by a stranger who bursts into the room and berates the instructor. After the incident, the students are asked detailed questions about the scene and the participants. Scores on the test show that complete accuracy is extremely rare, and the over-all average is seldom more than 30 per cent correct. What is more, many individuals are found to make the same error—which indicates that the law’s emphasis on consensus needs to be questioned. Analysis of the errors reveals that the witness is influenced by many factors: the element of surprise, the power of suggestion, emotional involvement, reactions to the individuals in the situation, mental and physical set, etc. Discussion of the test usually brings out additional factors that are likely to affect reports of accidents or crimes that occur on the street: distance from the scene, angle of vision, interference from other events, social attitudes (e.g., sympathy for the small-car owner), and the tendency to fill in gaps with plausible details.Experiments on interrogation procedures have shown that (1) free recitals are generally more accurate than reports in which the witness answers questions, especially when he is under cross- examination; (2) leading questions, questions with hidden assumptions, and negative phrasing (“Didn’t he have a gun?”) encourage false recall; and (3) asking a subject to indicate which facts he would report under oath tends to reduce errors. Other revealing studies have been made on differences in sentences imposed by different judges for the same crime, the tendency of jurors to be affected by social stereotypes and by the personality of the foreman, and the influence of the order in which evidence is presented. On the latter point, most courtroom studies show that the first and last positions (“primacy” and “recency”) tend to have equal effect, and a presentation which occupies a middle position between two presentations of the other side is at a particular disadvantage.Although psychologists were occasionally called to testify as expert witnesses at the time of Wilhelm Stern, it is only in recent years that their testimony has been sought with any degree of regularity. Clinical psychologists are now increasingly called upon to testify in commitment procedures for mental deficiency or mental illness, and in cases involving adoption, contested wills, accidents involving behavioral damage due to brain injury, and determination of legal responsibility for criminal acts. In addition, consumer psychologists are sometimes asked to present scientific data in suits involving misleading advertising or trade name infringements; and an ever larger number of social psychologists are serving as expert witnesses in cases involving racial discrimination and segregation. The trend in many states is to have the psychologist appointed by the court rather than by either side, and in such instances he either serves as an amicus curiae or is paid by both sides. The right of qualified psychologists to serve as a friend and adviser to the court in criminal cases involving the mental condition of the defendant was upheld by the United States Court of Appeals in 1962.Psychology in Correctional Institutions. In spite of the need for their services, relatively few psychologists are working in correctional settings today. In some cases, however, counseling or clinical psychologists are employed by courts, penitentiaries, probation departments, parole boards, and training schools. They serve on either a full- or part-time basis, or as consultants in individual cases, and they usually function in the role of adviser on diagnosis and treatment, but occasionally as therapists or research workers.Many juvenile courts as well as a few domestic relations and criminal courts have their own behavior clinics in which psychologists employ interviews and tests in evaluating the intelligence, personality characteristics, attitudes, and motivations of offenders. They may also assess their potential for vocational training, education, and job placement, and help to identify those who need special care due to neurosis, brain damage, mental defect, or psychosis. In some juvenile court clinics they engage in short-term psychotherapy or help to arrange for counseling of parents, remedial instruction, recreational programs, or foster-home placement. These approaches are often effective in salvaging youthful offenders.Still fewer psychologists are employed in prisons—about one for every three thousand inmates. Again the need is great, but it has often proved difficult for psychologists to function in this setting. In some prisons they are primarily concerned with interviewing and testing new admissions at the prison or at a special center prior to assignment to an institution. The results are then used in placing the inmates in work, educational, or vocational training programs. A similar evaluation procedure is undertaken for parole candidates, with emphasis on their adjustment to life in a community. A few prison psychologists engage in short-term individual or group therapy, sometimes using psychodra- matic techniques. They also help to develop training programs and discussion groups for normal inmates, and recommend the referral of the severely disturbed to special institutions.So far, only about one half of public training schools for delinquent boys or girls have full-time psychologists on their staff, and many of them do not even employ a part-time psychologist. In the institutions that do utilize their services, the emphasis is primarily on personality diagnosis, psychotherapy, and remedial educational programs. Activity therapy and play therapy may be used, and older children often receive vocational training and counseling.Finally, psychologists have begun to play a significant part in problems relating to international relations and international law. The Society for the Psychological Study of Social Issues, which became a division of the American Psychological Association in 1936, has published numerous papers on war and peace in its Journal of Social Issues. Symposia on these topics have been held at meetings of the American Psychological Association, and the organization now has a Committee on Psychology in National and International Affairs and an administrative officer for international affairs. Among the topics discussed in the past few years are the cold- war mentality, methods for resolving intergroup conflicts, national differences in personality, tensions affecting international understanding, factors underlying aggression, the value of student exchange programs, international cultural programs, techniques of conflict resolution, disaster reactions, responses to air raid warnings, and the use of simulated situations and political games in the study of conflicting interests.