IQ and intellectual disability relevance regarding sentence?
Following the case of Verdins it is an accepted legal principle that impaired mental functioning, whether temporary or permanent, is a relevant sentencing consideration and addresses the offender’s moral culpability and appropriateness as a vehicle for general deterrence.
The case sets out 5 principles as guidance in relation to whether Verdins should apply. However recent case law also demonstrates that Intellectual Disability and IQ are relevant sentencing considerations.
In R v Leeder both sitting Judges enlivened the issue of Intellectual Disability as a relevant sentencing consideration.
In delivering his judgment Justice Maxwell spoke of the need to consider intellectual disabilities as an important sentencing consideration, just as mental impairment has been addressed by the principles set out in Verdins. He stated that:
‘It seems to me important to ensure that this species of mental impairment is addressed with the same rigour and specificity as necessary in relation to the more familiar area of mental illness.’
Similarly Justice Buchannan opined when sentencing the offender who was deemed to have an IQ of 67:
‘Imprisonment is a blunt instrument, which is not designed to deal with the appellant,’
The case also raised relevant issues in relation to what equates to a ‘mild’ versus ‘severe’ intellectual disability, as there has been disparity in recent case law. Both Justices agreed that there is ‘scope for considerable refinement of expert opinion and therefore an argument before sentencing Courts about how the matters are to be taken into account’. 
In the more recent case of Muldrock v R the High Court reiterated to some degree the findings in Leeder. The Appellant in the matter was described as being mentally retarded and intellectually disabled, assessed as having an IQ of 62. The High Court held in this case that the Appellant was not a vehicle for general deterrence by virtue of his mental retardation and intellectual disability and quoted the following passage given by Justice Young:
‘General deterrence should often be given very little weight in the case of an offender suffering from a mental disorder or abnormality because such an offender is not an appropriate medium for making an example to others.’
The sentence was significant reduced in the context of more weight being given to the Appellant’s intellectual disability.