Skip to main content

The Use of the Macarthur Competence Assessment Tool: Criminal Adjudication in Evaluations of Competence to Stand Trial

1 January 2017


In the United States, a defendant’s competency to stand trial (CST) is protected under law. If the ability of the defendant to understand their legal case or assist in their defense is called into question, the case is suspended and the defendant is to be evaluated by a psychologist or psychiatrist. There is great variability in the structure of competency evaluations, with some professionals choosing to use tests and measures to inform their opinion while others rely on clinical judgment. One criticism of current CST evaluations is the lack of a clear relationship between a defendant’s mental illness and their impairment in competency-related abilities. The present study examined 65 competency to stand trial evaluations that utilized the MacArthur Competence Assessment Tool—Criminal Adjudication (MacCAT-CA) from a two Pacific Northwest private practices and a state hospital in the Midwest. Individuals opined competent performed significantly better on all three MacCAT-CA scales than those opined not competent. The impact of specific symptom presentations on scale performance was also investigated with two main findings: individuals with some form of cognitive impairment performed significantly lower on the Understanding scale than those without these impairments, and individuals with paranoid psychotic symptoms performed significantly lower on the Appreciation scale than those without paranoia. The present study contributes to research supporting the use of the MacCAT-CA in CST evaluations and demonstrates a relationship between particular symptoms and competency-related abilities. Further, the study highlighted potential differences among forensic evaluators about when and for what reasons they may elect to use this forensic assessment tool.


Files are restricted to Pacific University. Sign in to view.