Mental health professionals often conduct evaluations to assist courts in determining whether a criminal defendant is competent to participate in the adjudicatory process. A variety of instruments have been developed to help structure these forensic assessments; this entry describes one of the more contemporary competence assessment instruments, the MacArthur Competence Assessment Tool-Criminal Adjudication (MacCAT-CA).

In the United States, people accused of crimes have certain rights with respect to the adjudicatory process that are guaranteed by the Constitution. In particular, they have the Fifth Amendment protection against self-incrimination and rights articulated in the Sixth Amendment, which include the assistance of legal counsel, the right to confront their accusers, and the right to trial by a jury of their peers.

To benefit from these rights, defendants must be mentally competent to assert them. In Dusky v. United States (1960), the U.S. Supreme Court articulated specific functional abilities that defendants must have to participate competently in the adjudicatory process: They must be able to assist counsel, and they must have both a rational and a factual understanding of the proceedings against them.

Most, if not all, jurisdictions recognize only mental impairment—often characterized as “mental disease or defect”—as a basis for incompetence to proceed to adjudication. When questions about a defendant’s mental capacities arise, the courts almost invariably solicit the assistance of mental health professionals (primarily psychiatrists and psychologists) in resolving the issue. These forensic evaluators attempt to inform the court whether, and the extent to which, the defendant’s functional abilities required by Dusky are compromised by psychiatric problems.

Historically, the primary tool available to forensic examiners for assessing competence was the unstructured or semistructured interview. Although interview approaches can provide valuable information, they are vulnerable to a variety of sources of potential bias. For example, interview-based results from evaluations of the same defendant may be inconsistent because different examiners (a) asked questions that varied in content and/or difficulty, (b) had different subjective criteria for judging the adequacy of a defendant’s responses to various questions, or (c) used different reference groups or subjective algorithms for aggregating the information to formulate more focused conclusions about the defendant’s capacities.

The MacCAT-CA was designed to enable forensic examiners to collect information relevant to a defendant’s competence in a way that minimizes the influence of clinical subjectivity. The MacCAT-CA comprises three measures, each of which relates conceptually to one of the Dusky criteria. Each of these measures is described briefly below.

The Understanding measure includes 8 items that query issues such as the general roles and responsibility of the prosecuting attorney and defense attorney, the elements of a criminal offense, the responsibilities of a judge and those of a jury, the nature of criminal sentencing, and a defendant’s rights at trial. Thus, it relates to the Dusky requirement that a defendant have a “factual understanding” of legal proceedings.

The Appreciation measure includes 6 items that query the respondent about expectations regarding his or her pending case. These items relate to issues such as expectations about disclosing information to, and receiving assistance from, the attorney; the likelihood of being convicted; the likely severity of punishment if convicted; and expectations that one will be treated fairly by the courts. The respondent is asked to state his or her expectations and then explain the reasons for these beliefs. Scoring of these items involves a judgment of the plausibility of the defendant’s reasons for his or her beliefs—thus Appreciation relates to the Dusky requirement of a “rational understanding” of proceedings.

Finally, the Reasoning measure includes 8 items that require a defendant to exercise logical and reasoning skills in relation to legal information. Each of 5 items presents the respondent with two pieces of hypothetical information. These pieces of information are embedded in a hypothetical vignette (i.e., a man is arrested after getting into a fight at a bar) and the respondent is challenged to determine which piece of information has the greatest legal relevance for the hypothetical actor and to explain the basis for its greater legal relevance. Three other Reasoning items describe alternative dispositional choices for the hypothetical actor, proceeding to trial or accepting a plea agreement. The respondent’s task is to articulate comparisons and contrasts (e.g., conduct a risks-and-benefits analysis) between these choices, thus demonstrating the capacity to reason about legal alternatives. This measure is conceptually related to the Dusky requirement of “capacity to assist counsel.”

Three structural features of the MacCAT-CA limit the extent of interviewer subjectivity in the assessment. First, the administration is highly structured. The same 22 items are presented to each defendant, with instructions for both initial presentation and follow-up queries/probes to minimize examiner-related differences in the presentation. Second, explicit instructions and criteria are written for scoring each item, which minimizes differences in examiners’ judgment as to what is a correct or incorrect answer. Third, the total score for each measure (sum of item scores for Understanding, Reasoning, and Appreciation) is interpreted in light of norms based on a large, multistate sample of offenders recruited in jails and forensic psychiatric hospitals. Thus, statistical norms exist to guide clinical interpretation as to whether, and to what extent, a particular respondent manifests impairment in the functional legal abilities articulated in Dusky.

Research with adult offenders has demonstrated that the MacCAT-CA measures are reliable, with internal consistency estimates (Cronbach’s alpha) of .85, .81, and .88 for Understanding, Reasoning, and Appreciation, respectively. Interscorer reliability of .90, .85, and .75 for Understanding, Reasoning, and Appreciation, respectively, were reported in the MacCAT-CA manual. Evidence for the validity of the instrument includes that each measure correlates in expected ways with measures of intellectual capacity (positively) and with measures of psychotic symptomatology (negatively). Furthermore, poorer scores are obtained on MacCAT-CA measures by defendants who have been adjudicated incompetent to stand trial than by comparison groups of jail inmates awaiting trial. Finally, MacCAT-CA scores help to discriminate competent from incompetent defendants after controlling for measures of other constructs including demographic features, criminal history, and psychopathology variables.

Although the MacCAT-CA offers some advantages in terms of structuring and standardizing certain competence-related inquiries, it was designed to supplement, rather than to replace, the clinical interview in assessing adjudicative competence. It does not assess directly all the factors that might affect a defendant’s competence—for example, poor memory for events at or near the time of the alleged crime or incoherence of thoughts or speech that might make assisting counsel difficult. Furthermore, the clinician using the MacCAT-CA must still make judgments regarding symptoms of mental disorder and their contribution, if any, to poor performance on the MacCAT-CA. Thus, the MacCAT-CA is not a stand-alone measure of competence. It is best conceived as its name indicates— a “tool” to assist mental health professionals in their assessment of defendants’ competence-related abilities.


  1. Dusky v. United States, 362 U.S. 402 (1960).
  2. Otto, R. K., Poythress, N. G., Nicholson, R. A., Edens, J. F., Monahan, J., Bonnie, R. J., et al. (1998). Psychometric properties of the MacArthur Competence Assessment Tool-Criminal Adjudication (MacCAT-CA). Psychological Assessment, 10, 435-143.
  3. Poythress, N. G., Bonnie, R. J., Monahan, J., Otto, R., & Hoge, S. K. (2002). Adjudicative competence: The MacArthur studies. New York: Kluwer/Plenum.
  4. Stafford, K. P. (2002). Assessment of competence to stand trial. In A. M. Goldstein (Ed.), Handbook of psychology: Vol. 11. Forensic psychology (pp. 359-380). Hoboken, NJ: Wiley.

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