A forensic psychologist merges the practice of clinical psychology with the criminal justice system, applying knowledge of psychology to criminals, crimes, interrogation techniques, juries, development of correctional facilities, and many other things.

Forensic psychologists do clinical work, perform evaluations and assessments, provide treatment, and act as consultants. Forensic psychologists analyze past behavior, evaluate present behavior, and predict future behavior.

The practice of forensic psychology may be in criminal court, civil court, family court or the prison system. The common factor is the application of principals of clinical psychology to the treatment, evaluation, and profiling of both victims and criminals, requiring a thorough knowledge of both psychology and the law.

Forensic Psychology in Criminal Court

A forensic psychologist working in the criminal court system may work with the prosecuting attorney, the defendant’s attorney, or directly with the criminal. Some functions performed by a forensic psychologist in the criminal court system are:

• Assessing the competency of a criminal to stand trial
• Providing a psychological profile of the criminal
• Predicting the future behavior of the criminal
• Assessing a criminal’s sanity/insanity
• Providing clinical treatment to incarcerated criminals
• Evaluating the accuracy of eyewitness testimony
• Acting as jury consultants, assessing jurors and predicting verdicts
• Clinically treating sex offenders
• Evaluating child witnesses

Forensic Psychology in Civil Court

A forensic psychologist working in the civil court systems may work with the victim, for the defense, or for the prosecution, acting as an expert witness and/or providing clinical treatment. Some of the tasks of a forensic psychologist in the civil court system are:

• Working with offenders on anger management
• Treating an assault victim for PTSD (post-traumatic stress disorder)
• Assessing personal injury in accident cases
• Analyzing sexual harassment cases

Forensic Psychology in Family Court

In the family court system, the forensic psychologist works directly with the families and/or provides expert witness testimony to the court. Some of the duties of a forensic psychologist in the family court system are:

• Performing child custody evaluations
• Assessing visitation risk in divorce cases
• Evaluating termination of parental rights
• Mediating reconciliation (couple or family) plans
• Assessing circumstances of child abuse
• Providing clinical therapy to families
• Evaluating the home, the parents, and the child in child welfare cases

Not Guilty by Reason of Insanity

The McNaughton Rule was established in 1843, during the criminal trial of an Englishman named Daniel McNaughton. It stated that an accused person could be found not-guilty by reason of insanity if, at the time he committed the crime, he had such a "defect of reason" or "disease of the mind" that he did not know right from wrong.

This rule was supplanted by the Durham Rule in 1953, during the trial of Monte Durham. This rule stated that if a crime was perpetrated as the result of a "mental disease or mental defect" the accused was not guilty of the crime.

The Model Penal Code was developed in 1972; it continued the concept of not-guilty by reason of insanity, but added the caveat that a criminal who did not have the capacity to comprehend the gravity of his crime could not be held responsible for the crime.

In 1984, the Comprehensive Crime Control Act was signed into law; it states, similarly, that to stand trial, a criminal should be free of mental illness and comprehend the nature of the crime.

A forensic psychologist works to make this determination. Evaluation of the past and present behavior and capacity of the criminal, and prediction of his future behavior all point to his ability to stand trial. If he is tried and convicted, the forensic psychologist may provide information for his sentencing, and/or may clinically treat the criminal once he has entered the penal system.

Forensic psychologists provide a valuable service to the court system and the victims who seek justice there.