Psychological assessments are highly dependent on the forthrightness and sincere efforts of examinees. In particular, evaluations in forensic settings must consider whether feigning or other response styles are utilized to intentionally distort the clinical presentation. The current study examines the effectiveness of the Inventory of Legal Knowledge (ILK) at detecting feigned incompetency within a sample of jail detainees. As an ancillary goal, several scales of the Standardized Assessment of Miranda Abilities were included in the same within-subjects simulation design. Results of the total ILK score raised concerns regarding the mischaracterization of genuine offenders as "suggestive of feigning." Pending cross-validation, however, a Revised ILK proved highly effective, using a floor effect detection strategy. Although intended for Miranda-specific abilities, several detection strategies on the Standardized Assessment of Miranda Abilities appeared to be very promising within a broadened context of feigned incompetency.