At common law a mental impairment is a relevant consideration for sentencing purposes.
The leading authority is R v Verdins (2007) 16 VR 269² (Verdins), a decision of the Supreme Court of Victoria – Court of Appeal.
In Verdins, the Court unanimously held that mental impairment could be relevant to sentencing in at least six ways. Mental impairment could:
reduce an offender’s moral culpability for the offending conduct
be relevant to the kind of sentence that is imposed (and the conditions under which that sentence is to be served)
moderate or eliminate the weight afforded to the principle of ‘general deterrence’
moderate or eliminate the weight afforded to the principle of ‘specific deterrence’
cause a given sentence to weigh more heavily on an offender (as compared to a person who does not suffer from mental impairment)
justify the imposition of a lesser punishment if there is a serious risk that imprisonment would have a significant adverse effect on the offender’s mental health.
The fact that an offender suffers from mental impairment does not, of itself, justify the imposition of a lesser sentence. The extent to which an offender’s mental impairment is relevant to sentencing will depend on the nature and severity of the symptoms exhibited by a particular offender and the effect of the condition on that particular offender’s mental capacity.
These factors may be applicable where the offender is shown to have had a mental impairment at the time of the offending, at the time of sentencing, or both.