Introduction: Experts frequently assess competency in criminal settings where the rate of feigning cognitive deficit is demonstrably elevated. We describe the construction and validation of the Denney Competency Related Test (D-CRT) to assess feigned incompetency of defendants in the criminal adjudicative setting. It was expected the D-CRT would prove effective at identifying feigned incompetence based on its two alternative, forced-choice and performance curve characteristics.
Method: Development and validation of the D-CRT occurred in described phases. Items were developed to measure competency based upon expert review. Item analysis and adjustments were completed with 304 young teenage volunteers to obtain a proper spread of item difficulty in preparation for eventual performance curve analysis (PCA). Test-retest reliability was assessed with 44 adult community volunteers. Validation included an analog simulation design with 101 jail detainees using MacArthur Competency Assessment Test-Criminal Adjudication and Word Memory Test as criterion measures. Effects of racial/ethnic demographic differences were examined in a separate study of 208 undergraduate volunteers. D-CRT specificity was identified with 46 elderly clinic referrals diagnosed with mild cognitive impairment and dementia.
Results: Item development, adjustment, and repeat analysis resulted in item probabilities evenly spread from .28 to 1.0. Test-retest correlation was good (.83). Internal consistency of items was excellent (KR-20 > .91). D-CRT demonstrated convergent validity in regard to measuring competency related information and as well as malingering. The test successfully differentiated between jail inmates asked to perforfm their best and inmates asked to simulate incompetency (AUC = .945). There were no statistically significant differences found in performance across racial/ethnic backgrounds. D-CRT specificity remained excellent among elderly clinic referrals with significant cognitive compromise at the recommended total score cutoff.
Conclusions: D-CRT is an effective measure of feigned criminal incompetency in the context of potential cognitive deficiency, and PCA is assistive in the determination. Additional validation using knowns groups designs with various mental health-related conditions are needed.
Keywords: Assessment; competency; criminal; malingering; validity.