The Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV) (Wechsler, 2008) is a cognitive assessment that is often used in secure forensic settings, however it has not been normed on this population. The purpose of this paper is to develop forensic normative data.

Patient files in a high secure forensic hospital were reviewed in order to obtain completed WAIS-IV (Wechsler, 2008) assessments and scores from the five indexes (verbal comprehension, perceptual reasoning, working memory, processing speed and full scale intelligence quotient (FSIQ)). This included reviewing patient files from all directorates, including male mental health, male learning disability, male personality disorder and the women’s service, yielding a sample size of n=86.

The qualitative descriptors obtained across the hospital ranged between extremely low and superior. The learning disability service scored significantly lower than the mental health and personality disorder services in verbal comprehension index, perceptual reasoning index, working memory index and FSIQ, and significantly lower than the mental health, personality disorder and women’s services in processing speed index. Mean scores from this study were significantly lower in comparison to those from the UK validation study (Wechsler, 2008).

Practical implications
The significant difference between scores from the current study and those from the UK validation study (Wechsler, 2008) highlights the need to have appropriate normative data for forensic populations. Clinicians should consider interventions that may serve to increase cognitive function, such as cognitive remediation therapy.

Whilst several special group studies have previously been conducted, this study is the first to develop forensic normative data for the WAIS-IV (Wechsler, 2008). Whilst the sample size was relatively small with limited female participants, the data collated will enable clinicians working in forensic establishments to interpret their assessments in light of this information.

Lucinda Charlotte Flinn, Charlotte Louise Hassett, Louise Braham
Journal of Forensic Practice, 2018