ABSTRACT
In the authors’ experience, there is some confusion on the definition of offenders with intellectual and developmental disability (IDD) and who is included in this category. A variety of terms are used for the individuals to whom we will refer in the current chapter. In the UK and Ireland, we tend to use the term ‘learning disability’ while in the United States and many English-speaking countries the term ‘mental retardation’ was used for decades until recently when it was replaced by intellectual and developmental disability. In the UK we occasionally refer to ‘learning difficulty’, which can also be synonymous with IDDs. In a somewhat confusing categorisation, in some secure settings such as prison systems, the distinction between general or mainstream offenders and offenders with IDD has been different from the various diagnostic guidelines across the world. For example, in the English prison system offenders with lower intellectual functioning are defined by an IQ less than 80 and these individuals are often referred to as having ‘learning disability’ but, as we shall explain, this does not conform to international classifications. This is an important distinction because the international definition of IDD includes psychometrically assessed cognitive function indicating an IQ less than 70 and this alteration in the definition makes a significant difference to both prevalence and individuals concerned. In this chapter we will use the term IDD since it has gained international recognition.
