In the criminal court, forensic psychiatrists and psychologists are sometimes called upon as expert witnesses to answer questions relating to responsibility for a crime, dangerousness for reoffending (i.e. risk-assessment), and treatment for the prevention of reoffending given the presence of a mental disorder.
In forensic psychiatry and psychology one has to be extremely cautious because of the danger that criminal behaviors (abnormalities in a social way) may be labeled as mental disorders. A conflict between a person and public authority can never be held as a mental disorder per se. Someone committing an offense, and as such being socially deviant, is not mentally ill until proven so by the existence of a mental disorder.
There is now a large body of research showing that aggressive and delinquent individuals show distinct patterns of social information-processing across the six steps. At the first two steps, research suggests aggressive individuals experience a range of problems in encoding and interpreting social cues, leading to an inaccurate representation of the situation.
As a laboratory assistant in psychology at Radcliffe College, Marston (1917) had discovered a significant positive correlation between systolic blood pressure and lying, which became the basis of the modern polygraph. In fact, Marston was the psychologist who testified in the landmark case Frye v. U.S. (1923), the case that set the original standard for the acceptance of expert testimony in federal courts.
In the 1960s and early 1970s, correctional psychology as a subdiscipline of forensic psychology began to expand. Until then, and although there were exceptions, psychologists in correctional facilities focused more on classification than on treatment, both because the demand for diagnostic services was great and the obstacles relative to respecting confidentiality and achieving the trust of inmates were difficult to surmount.
Forensic psychology is a rapidly growing discipline. Currently, the American Psychology-Law Society has about 3,000 members, and the number continues to grow. Many experienced psychologists are seeking to respecialize into this field in order to escape the confines of managed care. Students are attracted to the field by our culture's growing absorption with all matters criminal, as well as fictional depictions such as TV's The Profiler and Criminal Minds.
In reality, most law enforcement agencies do not regularly use criminal profiling methods. When they do, they typically employ profilers with extensive backgrounds in law enforcement rather than in psychology. Perhaps more importantly, many scholars dispute that profiling even qualifies as a scientific method meriting inclusion in the behavioral sciences.
Current profiling practices typically involve some type of classification system, or typology, which is used to categorize both crime scene behaviors and offender background characteristics. By far the most routinely used typology is the FBI’s organized–disorganized dichotomy, which was developed from interviews with offenders (Ressler, Burgess, Douglas, Hartman, & D’Agostino, 1986). The assumptions underlying this typology are that (a) offenses can be categorized as organized (e.g., well planned) or disorganized (e.g., unplanned) based on the behaviors present at a crime scene, (b) offenders can be categorized as organized (e.g., high functioning) or disorganized (e.g., low functioning) based on the background characteristics of the offender, and (c) there is a correspondence between offenses and offenders (i.e., organized offenders commit organized crimes and disorganized offenders commit disorganized crimes).
The detection of deception is among the first practical applications of neurobiological measures to the criminal justice system. The polygraph ('lie detector') is the earliest and most well-known physiological measure of lie detection (Trovillo, 1939) and is based upon the assumption that autonomic responses (e.g. increased heart rate, blood pressure, respiration rate and skin conductance response) during questioning indicate anxiety and therefore lying.
For example, it is said that lawyers assume that, and that many laws - particularly criminal - are predicated upon, offenders have free will, in the sense that they 'choose' to commit their crimes. However, psychologists would emphasize factors indicating that such 'decisions' are constrained or even determined.