Written by Dr. Nicole M. Vienna

September 27, 2021


Competence within the criminal justice system is a concept of law that allows for criminal proceedings to be postponed for individuals who are deemed incompetent to stand trial. Competency refers to the defendant’s capacity to participate in their defense and make decisions during the trial process. Incompetency can be evaluated or declared at different points during criminal proceedings, from the time of the arrest to sentencing (Wiener & Otto, 2013). This article will focus on competence to stand trial, as that is the most commonly evaluated area of competence.

Why Should Competence Be Determined For Criminal Proceedings?

Legally, competence is an important aspect of criminal proceedings, as the conviction of a defendant who is mentally incompetent violates due process. Per 18 U.S.C. § 4241(a), the court must order a competency hearing if “…there is reasonable cause to believe the defendant may presently be suffering from a mental disease or defect rendering him mentally incompetent to the extent that he is unable to understand the nature and consequences of the proceedings against him or to assist properly in his defense” (Department of Justice [D.O.J.], 2020). A hearing may be requested by a motion from the defense, the prosecution, or the court. In accordance with Department of Justice standards, competency evaluations consist of a psychiatric or psychological evaluation, which produces a report that is submitted to the court. While forensic psychologists make an evidence-based statement declaring the defendant incompetent in their report, the final ruling of competence is made by the court after reviewing the report (D.O.J., 2020). Thus, forensic psychologists play an important role in competency decisions.

As with all forensic work, forensic psychologists are held to a high standard regarding the accuracy, reliability, and validity of their reports. When conducting a competency evaluation, forensic psychologists can utilize various instruments to obtain data about a defendant. This data is then collectively evaluated by the psychologist to determine if the defendant is competent. Generally, there is a high level of inter-rater reliability for competency evaluations, and research has found that consistency between evaluators is bolstered when psychologists are highly trained and use semi-structured assessment instruments (Wiener & Otto, 2013). Thus, it is important for competency evaluations by forensic psychologists to utilize a standardized approach to ensure reliability and validity.

Conducting a Competency Evaluation

Along with a clinical interview, some psychologists may choose to administer psychological testing for various reasons. Instruments for evaluating competency were first introduced in the 1960s, with the development of a checklist by Robey (1965). Since that time, more measures have been developed, such as the Competency Screening Test (Lipsett et al., 1971), the Competency Assessment Instrument (McGarry, 1965), the Interdisciplinary Fitness Interview-Revised (Golding, 1993), the Fitness Interview Test, Revised (Roesch et al., 2006), the Georgia Court Competency Test (Wildman et al., 1978), the MacArthur Competence Assessment Tool – Criminal Adjudication (Hoge et al., 1999), the Evaluation of Competency to Stand Trial – Revised (Rogers et al., 2004), and the Inventory of Legal Knowledge (Otto et al., 2010). All of these instruments include various questions and scoring systems that assess a defendant’s understanding, reasoning, communication, and effort in the context of their case and the legal system.

In addition to conducting a thorough clinical interview, forensic psychologists will also review the case information, interview family members or treatment providers, and possibly conduct specific neuropsychological assessments that evaluate cognitive functioning (Wiener & Otto, 2013). An example of this is the Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV) that assesses an individual’s memory, processing speed, verbal fluency, and intellectual functioning through various subtests. A psychologist can obtain an individual’s full-scale I.Q. score from the WAIS-IV, which can also be used to shed light on cognitive abilities that are necessary for competency. The results from these tests provide the forensic psychologist with information regarding the defendant’s mental state, intellectual functioning, cognitive ability, decision-making capacity, and understanding of legal proceedings, which are all important factors needed to meet the standard for competency. Moreover, the interview and evaluation data support whether or not the individual is suffering from a mental disorder or developmental delay. This is important because under California law, specifically Penal Code section 1367(a), a defendant is only mentally incompetent to stand trial if, as a result of a mental disorder or developmental disability, he cannot (1) understand the nature of the criminal proceedings, or (2) assist counsel in the conduct of a defense in a rational manner.

After conducting the evaluation, the forensic psychologist will write a comprehensive report summarizing the data collected, observations, and clinical impressions (UMass Chan Medical School, n.d.). The report will also contain background information about the defendant that is relevant to the evaluation and provides support for the psychologist’s subsequent clinical opinion. In addition, the report will include a description of the defendant’s current mental functioning and an outline of their abilities relevant to competence to stand trial, such as understanding of the charges and potential consequences, understanding of the trial process, ability to assist counsel in their defense, and decision-making capacity. Finally, the report will include a clear statement of the psychologist’s clinical opinion regarding competence, citing data from the assessments, clinical interviews, and relevant history. Often, the psychologist will also make recommendations for treatment of the defendant or restoration of competency (i.e., hospitalization, community treatment) (UMass Chan Medical School, n.d.).

In summary, the task of determining criminal competency is a systematic, standardized process that requires a forensic psychologist to understand legal standards for competency, conduct a thorough clinical interview, and possibly assess an individual with the use of reliable, valid measures, and synthesize all data points to determine if the individual meets the legal requirements to proceed in court. Forensic psychologists assess an individual’s mental functioning, decision-making capacity, understanding of the legal process, ability to aid in their defense, and recognition of their charges and potential outcomes (D.O.J., 2020; Wiener & Otto, 2013). They also consider an individual’s psychiatric history, I.Q. score, presence of any developmental or intellectual disability, and any current psychiatric diagnoses. As outlined in this article, the process of determining competency must be completed by a highly trained professional, grounded in data collection, supported by adequate evidence, and free of bias or prejudice.

For more information about criminal competency or to schedule a consultation appointment with Dr. Vienna, call our office at (626) 709-3494.


Department of Justice. (2020, January 17). Standards for Determining Competency and For Conducting a Hearing. The United States Department of Justice Archives. https://www.justice.gov/archives/jm/criminal-resource-manual-63-standards-determining-competency-and-conducting-hearing

Golding, S. L. (1993). Interdisciplinary Fitness Interview-Revised: A training manual. Department of Psychology, University of Utah, Salt Lake City, UT. Available at http://home.comcast.net/∼slgolding/publications/ifir_manual.htm

Hoge, S. K., Bonnie, R. J., Poythress, N., & Monahan, J. (1999). The MacArthur Competence Assessment Tool—Criminal Adjudication. Odessa, FL: Psychological Assessment Resources.

Lipsitt, P. D., Lelos, D., & McGarry, A. L. (1971). Competency for trial: A screening instrument. American Journal of Psychiatry, 128, 105–109.

McGarry, A. L. (1965). Competency for trial and due process via the state hospital. American Journal of Psychiatry, 122, 623–631.

Otto, R. K., Musick, J. E., & Sherrod, C. B. (2010). Inventory of Legal Knowledge professional manual. Lutz, FL: P.A.R.

Robey, A. (1965). Criteria for competency to stand trial: A checklist for psychiatrists. American Journal of Psychiatry, 122, 616–623.

Rogers, R., Tillbrook, C. E., & Sewell, K. W. (2004). Evaluation of Competency to Stand Trial–Revised (ECST-R) and professional manual. Odessa, FL: Psychological Assessment Resources.

Roesch, R., Zapf, P. A., & Eaves, D. (2006). Fitness Interview Test: A structured interview for assessing competency to stand trial. Sarasota, FL: Professional Resource Press.

UMass Chan Medical School. (n.d.). Competency Evaluation Report Writing Guidelines. https://www.umassmed.edu/forensictraining/reports/competency-evaluation-report-writing-guidelines/

Wiener, I.B., Otto, R.K. (2013). The Handbook of Forensic Psychology (4th ed.). John Wiley & Sons, Inc.

Wildman, R. W., Batchelor, E. S., Thompson, L., Nelson, F. R., Moore, J. T., Patterson, M. E., & Delarosa, M. (1978). The Georgia Court Competency Test: An attempt to develop a rapid, quantitative measure of fitness for trial. (Unpublished manuscript). Forensic Services Division, Central State Hospital, Milledgeville, GA.

Penal Code 1367 https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PEN&sectionNum=1367.

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