Written by Dr. Nicole M. Vienna

March 29, 2022

Expert witnesses give their opinion on a subject area to the court. They are widely used in criminal and civil legal matters. The courts and legal system have relied upon expert witnesses in mental health fields since the 18th century. In California, under evidence code 720, a person is qualified to testify as an expert if they have specialized knowledge, skill, experience, education, or training sufficient enough to qualify them as an expert in a said subject area relevant to their testimony. The expert has to be qualified in the court by the judge or commissioner of the court. Specifically, a forensic psychologist can serve as an expert witness to provide oral testimony in court, write a forensic report answering a psycho-legal question, and provide a consultation.

1. Oral Testimony/Sworn Deposition. An oral testimony, or sworn deposition, is when an expert is called to court to either provide additional or clarifying expert opinions on a case they were working on or provide expert opinion on a said subject. For example, an expert in post-partum depression may be called to the court to give expert opinions on the said subject matter. Forensic psychologist expert witnesses can also testify about an individual (defendant or plaintiff) they evaluated and opine on the person’s cognitive, behavior, emotional, and mental health status as it relates to their capacity to proceed, criminal responsibility, future violence risk, ability to waive their Miranda rights, insanity, workplace injuries, and other psycho-legal matters. The expert witness should have the appropriate education, training, and experience to provide testimony in the court or deposition.

Expert witnesses’ credibility, integrity, and qualifications are often challenged by the opposing party. For this reason, it is highly recommended that experts are comfortable with the adversarial process, fielding pointed questions and working under pressure. Furthermore, attorneys often obtain experts by word of mouth; a positive reputation is everything. And your reputation will be based on your work (reports, consultations with attorneys, and testimony). In addition, successful expert witnesses employ skills such as being able to form defensible opinions, meeting deadlines, being dependable, exceeding expectations, writing understandable reports, and articulating your opinion well.

2. Forensic Reports. One of the most common reasons forensic psychologists are used as expert witnesses is to provide the retaining party (the court, attorney, or legal decision-maker) a professional clinical opinion about a psycho-legal question. The forensic psychologist expert witness typically holds a doctorate degree in clinical or clinical forensic psychology and is licensed in the state they are performing work. They specialize in various areas, such as child or adolescent psychology, neuropsychology, cognitive psychology, geriatric psychology, trauma, etc.

The main purpose of the forensic report is to educate or inform the trier of fact or retaining party. The expert will often conduct an evaluation or clinical interview and summarize their findings within the report as succinctly as possible. The report is the coveted work product that should convey the expert’s data, findings, and forensic opinion in an understandable matter. To that end, writing forensic reports requires excellent verbal and written communication skills. In addition, the expert needs to be trained in and follow forensic report writing best practices.

The main components of forensic report writing include answering the referral question, using appropriate language, writing for the intended reader, appropriately interpreting mixed data, not including irrelevant data, relying on multiple sources of data, using appropriate psychological tests, considering alternative hypotheses, and forming opinions with adequate explanation.

3. Consultation. Because forensic psychologist expert witnesses are, first and foremost, licensed psychologists that apply their specialized knowledge of clinical psychology to a psycho-legal question or legal matters, they’re exceptionally skilled at providing attorneys with information related to treatment recommendations, evaluations of the potential risk of future violence, voir dire (jury selection), witness preparation, sentencing recommendations, etc. In addition, anytime there is an element of human behavior involved in a legal matter, the expert witness’s opinion is extremely useful in conveying the connection between the brain, the behavior, and the law.

Furthermore, expert witnesses can review records and provide feedback to the retaining party about trial strategy and case analysis. They can guide the attorney on the type of evaluation that might be needed or most fruitful. Expert witnesses conducting forensic consultation can even review the work of another expert witness and provide questions for cross-examination.

Regardless of which of the three common areas forensic psychologists act as expert witnesses, all the categories require a significant amount of work, including research, evaluation, analyzing data, and testimony or deposition preparation. Therefore, it is most helpful for the retaining attorney and the retained expert witness to have several transparent conversations throughout the process of the case. This not only negates anxiety on the expert’s part but also prepares them sufficiently to do the job they are hired to do.

Tips for Attorneys Looking for Forensic Psychologist Expert Witnesses:

  • Schedule a consultation call with the expert. Experts are extremely busy working on their cases just as you are. Set aside a block of uninterrupted time to overview your case.
  • Inquire about the expert’s educational background, training, and experience in the subject area you need for your case.
  • Be very clear and transparent about what you are looking for from the beginning. It is most helpful when experts have a working knowledge of the attorney’s strategy and referral question.
  • Prepare the referral questions in advance.
  • Start requesting records (family, medical, psychiatric, employment, etc.). You can inquire about relevant records to request during the consultation if you are unsure. The sooner, the better.
  • Ask the potential expert some possible questions you expect them to answer during cross-examination or deposition. This will give you a good idea of how they organize their thoughts and express expert opinions in the said subject area on the spot!
  • Don’t forget to obtain a copy of your expert’s C.V. and verify their education, experience, and training.

Forensic psychologist expert witnesses are an important part of the judicial system. They can serve in various roles, from providing expert testimony or sworn deposition, consultation services, and providing forensic reports. This niche area of practice requires extensive education, training, and experience to obtain expert qualifications in court. To that end, forensic psychologist expert witnesses have unique skill sets in the assessment of persons’ cognitive, behavioral, and mental health status as it relates to legal matters. Expert witness work proves to be invaluable when a person is facing a lengthy criminal sentence, a dispute over custody of their children, the maintenance of victim rights, an injury while in the workplace, an accusation of medical malpractice, an act of financial litigation, etc.

The team at Vienna Psychological Group includes a forensic psychologist who is available to serve as an expert witness. Contact our office at (626) 709-3494 to schedule a consultation.




Brannick, Meghan E., “Guidelines for Forensic Report Writing: Helping Trainees Understand Common Pitfalls to Improve Reports” (2015). Graduate School of Professional Psychology: Doctoral Papers and Masters Projects. 63. https://digitalcommons.du.edu/capstone_masters/63

How to get started as an Expert Witness. White Paper by By James J. Mangraviti, Jr., Esq., Nadine Nasser Donovan.

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