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To be competent to stand trial in the US legal system, defendants generally have to be able to understand the legal proceedings and be able to work with their attorney (Dusky v. United States, 1960). Given the incentives to feign impairment during competency to stand trial (CST) evaluations, evaluators must be able to assess accurately for malingering (Conroy and Kwartner, 2006). Several instruments have been developed for this purpose, each of which typically focuses on either malingered cognitive deficits or malingered psychiatric symptoms. Recently, the Inventory of Legal Knowledge (ILK) was developed to evaluate malingered deficits specific to CST, including defendants’ knowledge of the legal process, the roles of different parties involved, and the capacity to meaningfully assist one’s attorney (Otto et al., 2010, 2011; Musick and Otto, 2010). Given this, the ILK has the potential to become widely used in CST evaluations in the USA.
In one of the first ILK validation studies, Guenther and Otto (2010) examined the psychometric properties of the ILK with a sample of college students and a sample of psychiatric inpatients. Using a simulation design, participants in both samples were randomly assigned to one of two conditions; honest or fake bad. In order to assess test-retest reliability, 60 of the college students were administered the ILK twice. Results showed the ILK to have acceptable test-retest reliability (r=0.76), although this was considered to be partially due to practice effects. Further, participants in both samples assigned to the fake bad condition earned lower scores, on average, relative to those assigned to the honest responding group, providing preliminary validity support for the ILK.
In a subsequent validation study, the convergent validity of the ILK was examined using the Rey-Fifteen-Item Test (FIT), Reliable Digit Span (RDS), and the Test of memory Malingering (TOMM) (Otto et al., 2011). Demographic information and test data were taken from 120 adult pretrial defendants undergoing competency evaluations in two southeastern states in the USA. All participants were administered the ILK, 59 were administered the Rey-FIT, 34 were administered the RDS, and 29 were administered the TOMM. All three of these widely used measures of response style showed strong relationships (p<0.01) with the ILK, providing support for the ILK’s convergent validity...