Forensic Clinician’s Tool Box: Competency to Stand Trial measures

Assessment psychologists need a wide range of tools to address the variety of assessment challenges that arise in daily practice.  Not that different from a set of wrenches and scredrivers designed for every type of bolt and screw. It is perhaps not surprising that many psychologists persist in using “traditional” assessment measures in forensic psychological assessment (MMPI, WAIS, Rorschach, etc.). This has been a source of appropriate criticism. As the range of forensic psychological assessment  has widened, a new set of tools has emerged: forensic assessment  instruments (FAIs). They are designed to address specific legal issues. The use of these measures enhances the quality and rigor of the assessment report, findings, conclusions, and opinions. We will look at several tools for Competency to Stand Trial (CST) first.

The Forensic Clinician’s Toolbox I: Review of  Competency to Stand Trial (CST) Instruments

Note: The Forensic Clinician’s Toolbox focuses on emerging forensic assessment instruments with utility in enhancing the quality and admissibility of forensic psychological assessment reports. The section will focus on applications in both criminal and civil forensic psychology, including criminal (competency to stand trial, criminal responsibility) and civil competencies, (testatmentary capacity, assessment for guardianship), malingering, and violence risk.

It appears indisputable that assessment psychologists previously working in mental health settings have extended their interest to forensic psychological assessment. Otto and Heilbrun (2002) distinguish between three types of assessment instruments used in forensic settings: a) clinical measures and assessment techniques: “psychological testing measures developed for assessment, diagnosis, and treatment planning with clinical populations in therapeutic contexts”; b) forensically relevant instruments: measures that “do not assess or focus on specific legal standards and the associated functional capacities of the examinee… rather they address clinical constructs that are often pertinent to evaluating persons in the legal system”; and c) forensic assessment instruments: “measures that are directly relevant to a specific legal standard and reflect and focus on specific capacities, abilities, or knowledge that are embodied by the law.”

The quality of forensic assessment reports depends heavily upon the procedures and instrumentation relied upon by the clinician (Robinson & Acklin, 2010).  The Forensic Clinician’s Toolbox will focus on various domains of forensic psychological assessment and a survey of tools to assess relevant constructs (competency to stand trial, criminal responsibility, etc.).  There are a number of measures informally and commercially available for evaluating CST. We will focus first on published, readily available measures designed to assess CST: The MacArthur Competence Assessment Tool-Criminal Adjudication (MacCAT-CA; 1999); the Evaluation of Competency to Stand Trial-Revised (ECST-R; 2004); and the recently published Inventory of Legal Knowledge (ILK; 2010). More detailed reviews of the MacCAT-CA and the ECST-R are found in Melton, Petrila, Poythress, & Slobogin, 2007.

Adjudicative Competence is best conceptualized in the work of University of Virginia Law Professor, Richard Bonnie (1992), who distinguishes between “basic” and “decisional” competency –factors deriving from the 1960 United States Supreme Court case, Dusky v. US (1960). “Basic” competence includes understanding of charges, concept of a criminal defense, knowledge of judicial concept and procedures, and general ability to work with defense counsel. “Decisional” competence, on the other hand, assesses the quality of the defendant’s reasoning process–the rational prong of  Dusky CST criteria. CST evaluations typically involve a clinical and forensic interview, and administration of clinical, forensically relevant, and forensic assessment instruments depending on the evaluator’s strategy (Robinson and Acklin, 2010).

The MacCAT-CA, developed by the MacArthur Foundation Research Network on Mental Health and the Law, is the queen of CST instruments.  The 22-item measure assesses three Dusky-derived competence-related abilities: understanding, reasoning, and appreciation.  The instrument was normed on adult defendants. Defendant’s capacities are assessed through responses to a series of vignettes.  Scores for each vignette are summed and compared to three groups of defendants (N = 729), including unscreened jail inmates, jail inmates receiving mental health services, and hospitalized incompetent defendants. Normative interpretation of MacCAT-CA scores include minimal/none, mild, and clinically significant impairment.  The psychometrics of the measure is well detailed in the manual. Although the vignette methodology has received some criticism, in this reviewer’s opinion, the primary strength of the measure is the opportunity to evaluate the quality of the defendant’s reasoning: the basis for decisional competency.  The open response format seems particularly sensitive to the infiltration of impaired reasoning. The professional manual provides a conceptual background for the instrument and detailed exposition of norms, reliability, and validity information. The administration time typically requires 25-45 minutes.

The ECST-R, developed by Richard Rogers and his colleagues, is a hybrid interview organized into separate semistructured and unstructured components, designed for use “as a validated psychological measure for competency to stand trial and closely related psycholegal constructs” (Rogers, Tillbrook, & Sewell, 2004).  The measure is designed for individuals 18 years of age or older, for individuals with IQs greater than 60, with English-speaking populations.  The measure provides a number of scales derived from the Dusky standard: ability to consult with counsel, factual understanding of court proceedings, rational understanding of courtroom proceedings, and reflecting Rogers’s ongoing interest, atypical presentation, which assesses response style and potential attempts to feign incompetence. Here too the psychometric properties of the measure are quite strong and the manual details the research foundations of the measure.

The ILK, despite its title, “is not a test of an adjudicative competence.  High scores on the ILK do not indicate that the defendant is knowledgeable about the legal process or competent to proceed, and low scores do not indicate that a defendant is uninformed about the legal process or incompetent to proceed.  The ILK is solely a measure of response style.” (Otto, Musick, & Sherrod, 2010, p. 4).  The 61-item true-false inventory is designed for English-speaking persons ages 12 years or older.  The inventory is examiner administered.  The test is designed to “detect feigned deficits in legal knowledge” using a methodology similar to symptom validity approaches with normative comparisons to five groups of defendants.  The normative base of the measure is limited to two pilot studies (N = 145). The authors note that the ILK has not likely attained “general acceptance” for the purposes of expert testimony.

Having administered all three CST measures, the Mac-CAT-CA and ECST-R, seem to be indispensable for the forensic clinician’s toolbox.  On the negative side, they are insufficient in their sampling of knowledge about judicial and legal terms and procedures (best accomplished through a detailed interview). They are complex measures that require thorough understanding of the underlying legal standards, constructs, rationale, and administration, scoring, and interpretation procedures.  Integration of these measures into the forensic clinician’s regular practice will require study of the measures, repeat administrations and careful consideration of their role in the clinician’s assessment strategy and reporting.  The ILK, on the other hand, is a more limited measure and appears useful as an adjunctive measure of the defendant’s response style, particularly on issues of faking ignorance of basic legal knowledge.


 Bonnie, R.  J. (1992). The competence of criminal defendants: A theoretical reformulation.  Behavioral Sciences and the Law, 10, 291-316.

 Dusky v. US, 362 US 402 (1960).

 Melton, G., Petrila, J., Poythress, N.G., & Slobogin, C. (2007). Psychological Evaluations for the Courts: A handbook for mental health professionals and lawyer. New York: Guilford Press.

 Otto, R.  K., & Heilbrun, K.  (2002). The Practice of Forensic Psychology: A look toward the future in light of the past.  American Psychologist, 57, 1, 5-18.

 Poythress, N.G., Nicholson, R., Otto, R. K., et al. (1999).  The MacCAT-CA: The MacArthur Competence Assessment Tool-Criminal Adjudication Professional Manual.  Lutz, Florida: Professional Assessment Resources, Inc.

 Otto, R. K., Musick, J. E., and Sherrod, C. B. (2010). ILK: Inventory of Legal Knowledge Professional Manual.  Lutz, a Florida: Professional Assessment Resources, Inc.

 Robinson, R., & Acklin, M. (2010).  Fitness in Paradise: Quality of Forensic Reports Submitted to the Hawaii Judiciary.  International Journal of Law and Psychiatry, 33, 3, 131-137.

 Rogers, R., Tillbrook, C. B., & Sewell, K. W. (2004). ECST-R: Evaluation of Competency to Stand Trial-Revised Professional Manual.  Lutz, Florida: Professional Assessment Resources, Inc.


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