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Evaluating feigning in individuals with intellectual disabilities in criminal cases: a cautionary tale

Michael Vitacco (Institute of Public and Preventive Health, Augusta University, Augusta, Georgia, USA)
Alynda Randolph (Department of Psychology, JBS Mental Health Authority, Birmingham, Alabama, USA)
Kaitlyn Soroko (Institute of Public and Preventive Health, Augusta University, Augusta, Georgia, USA)
Janina Velez (Department of Psychology, The Chicago School of Professional Psychology, Chicago, Illinois, USA)
Diandra Sigurdsson (Minnesota Department of Human Services, Saint Paul, Minnesota, USA)

Journal of Intellectual Disabilities and Offending Behaviour

ISSN: 2050-8824

Article publication date: 7 December 2022

Issue publication date: 3 April 2023




Response style evaluation is a fundamental component of forensic examinations. This retrospective study aims to evaluate how measures of feigning performed with individuals with intellectual disabilities (ID) who were undergoing competency to proceed to trial evaluations.


Using a known-groups design (ID vs non-ID) with 145 individuals, 37 individuals met diagnostic criteria for ID. The individuals were administered the Miller Forensic Assessment of Symptoms Test (M-FAST; Miller, 2001), the Inventory Legal Knowledge (ILK; Musick and Otto, 2010), the Evaluation Competency to Stand Trial-Revised, atypical presentation scale (ATP; Rogers et al., 2004b) and the Competence Assessment for Standing Trial-Mental Retardation (Everington and Luckasson, 1992).


The total ILK demonstrated differences between groups with a large effect size (Cohen’s d = 1.02). Six items on the ILK had over a 30% difference as a function of group. However, two revised scales from the ILK, the R-ILK-90 and the R-ILK-95 (Rogers et al., 2017), did not demonstrate differences as a function of group membership with small effect sizes (Cohen’s ds = 0.02 and 0.29). The M-FAST total score and ATP scales were not different between groups, although results demonstrated that individuals with ID would be potentially more at risk to for misclassification as feigning on the M-FAST.

Research limitations/implications

This study has several limitations. It is a retrospective study with a relatively small sample size so additional research is needed to substantiate the results. However, this study highlights the potential for individuals with intellectual disabilities to be disadvantaged when undergoing competency to stand trial evaluations.

Practical implications

This manuscript shows that individuals with ID are at-risk for being mislabeled as feigning when employing standard measures of response style testing if appropriate cautions are not used. However, revised measures that take into account baseline information of legal knowledge offer a way forward that may prevent false positives with individuals with ID.

Social implications

The mislabeling of individuals with ID could lead to significant problems, including harsh sentences and unnecessary incarcerations. This manuscript provides real-world data and encourages clinicians to be mindful when evaluation individuals with ID for court-ordered evaluations.


This manuscript is critical, as it shows that caution is needed when using instruments of feigning with individuals with ID who are undergoing competency evaluations. This has value for clinicians who are tasked with completing these evaluations for the courts.



Vitacco, M., Randolph, A., Soroko, K., Velez, J. and Sigurdsson, D. (2023), "Evaluating feigning in individuals with intellectual disabilities in criminal cases: a cautionary tale", Journal of Intellectual Disabilities and Offending Behaviour, Vol. 14 No. 1, pp. 1-13.



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