Accurate assessment of the response styles criminal defendants adopt when undergoing evaluations of their competence to proceed with the legal process is critical because some feign limitations in their abilities in an attempt to delay or avoid prosecution. This study examined the utility of the Inventory of Legal Knowledge (ILK) to identify persons motivated to feign competence related limitations. That the ILK has good potential as a screening tool is indicated by findings that the measure (1) has adequate test–retest reliability and (2) classified correctly the large majority of participants in two samples (i.e., college students and psychiatric patients) who completed the measure under “honest” or “fake bad” conditions. Copyright © 2010 John Wiley & Sons, Ltd.