Forensic neuropsychology is the application of neuropsychology principles in diagnosing and treating individuals involved in civil and /or criminal matters within the justice system. It involves understanding the law in order to be able to interact appropriately with judges, attorneys, and other legal professionals. Forensic neuropsychologist performs a wide range of tasks within the criminal justice system. The largest is preparing for and providing testimony in the court room. Evaluating the client, preparing testimony, and the testimony itself require the forensic neuropsychologist to have a firm grasp of the law and legal situation at issue in the courtroom. Forensic neuropsychologists are generally asked to appear as expert witnesses in court to discuss cases that involve issues with the brain or brain damage. Neuropsychologists also deal with the issue of whether a person is legally competent to stand trial. The main roles of a neuropsychologist in the court system are as following:
- Evaluation of possible malingering
- Assessment of mental state for insanity plea
- Competency to stand trial
- Prediction of violence and assessment of risk
- Assessment of personal injury
- Specialized forensic personality assessment
Forensic Neuropsychologists have the ability to express an opinion because they are "expert" in their field. They possess specialized knowledge about the topic. Expert witnesses are called upon to testify on matters of mental health (clinical expertise) or other areas of expertise such as social, cognitive, and developmental.