Written by Dr. Nicole M. Vienna

September 30, 2021


In a criminal case, a forensic psychologist plays the role of a neutral third party to the court. This means that they are to maintain an impartial and objective role as the retained forensic psychologist of the case. Therefore, the field of forensic psychology demands professionals maintain and practice high standards of ethics and integrity. In fact, forensic psychology is the only specialty from the American Psychological Association (APA) that has its own set of specialty guidelines and ethics.

A forensic psychologist conducts psychological evaluations of the individual (defendant) to answer legal questions from the referring party. The referring party could either be the court, the prosecutor, or the defense attorney. These types of psychological evaluations can assist with the legal decision-making process. Forensic psychologists apply psychological principles, research, and knowledge to these legal questions brought up in the criminal case. Examples of legal questions are:

  • Does the defendant have a fundamental understanding of the proceedings against him?
  • Does the defendant understand the role of his attorney, judge, prosecutor, etc.?
  • Does the defendant understand what he is being charged with?
  • When the defendant committed the crime[s], did they have a mental disease or defect; AND because of that disease or defect, was the defendant incapable of knowing or understanding the nature and quality of their actions, or were they incapable of knowing or understanding that their act was morally wrong.

Still, there are other questions a forensic psychologist may be asked to address in a written report. For example, in mental health diversion (PC1001.36) evaluations, the questions consist of addressing whether the defendant suffers from a mental disorder, whether the mental disorder substantially contributed to the defendant’s involvement in the commission of the offense, whether the defendant’s symptoms motivating the criminal behavior would respond to mental health treatment, whether the defendant agrees to comply with treatment as a condition of diversion, and whether the defendant will pose an unreasonable risk of danger to public safety if treated in the community.

Another common referral for a forensic psychologist in a criminal case is when defendants are found guilty. The defendants’ attorneys often would like to present information to the court that could mitigate or lessen the defendant’s sentence.

Forensic psychologists diligently practice within their area of expertise and provide information to the trier of fact (judge) in making a legal determination. Not only can this information be offered in the form of a written report, but it can also be offered as expert testimony. In this case, forensic psychologists are retained as expert witnesses on a specific subject matter and testify in court. The role of the expert witness is to inform or educate the judge or jury on the defendant’s psychological makeup or a said subject area, such as the impact of high concentrations of alcohol on cognitive abilities.

In sum, forensic psychologists play a unique and imperative role in criminal cases. This is because people’s lives are on the line, sometimes quite literally. As such, a forensic psychologist will not only spend a significant amount of time maintaining specialized training but will dedicate several hours to a case. Sometimes this involves upwards of 40-50 hours. This includes conducting thorough clinical interviews with the defendant, family members, witnesses, treatment providers and reviewing records (police reports, detective interviews, treatment records, jail files, criminal records, etc.). A forensic psychologist will also conduct psychological testing, score and analyze the data, and prepare a written report when warranted.

To schedule an appointment with forensic psychologist Dr. Vienna, contact our office at (626) 709-3494.

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