The MacArthur Competence Assessment Tool-Fitness to Plead: a preliminary evaluation of a research instrument for assessing fitness to plead in England and Wales.

This study concerns the preliminary evaluation of an instrument, the MacArthur Competence Assessment Tool-Fitness to Plead (MacCAT-FP), for assessing competence to stand trial, according to the legal requirements in England and Wales. The purposes of the study were to ascertain whether the instrument can be administered practically to groups of prisoners, both those with mental illness and those without; to examine its internal consistency and interrater reliability; to determine whether it can distinguish between fit and unfit individuals, as judged by expert forensic psychiatrists; and to discover whether it is sensitive to changes over time. The instrument was administered to two groups of remanded prisoners: those transferred to psychiatric units for treatment and those without mental illness. In addition to the MacCAT-FP, scales measuring symptom severity and IQ were administered to all participants. Results suggest that the instrument is practical, with good internal consistency and interrater reliability. The correlation of scores with psychiatrists' opinions as to fitness was 0.77. Scores of unfit patients were significantly different from those of fit individuals. The instrument was able to detect significant differences in scores over time. It is suggested that once the instrument has been further validated for research purposes, it may be developed for clinical application.