The Court of Appeal held that the use of the phrase 'to such an extent' in a jury checklist describing the threshold for the defence of mental impairment under s 20(1)(b) of the Crimes (Mental Impairment and Unfitness to be Tried) Act 1997 did not impermissibly elevate the standard of proof, as it was consistent with the common law test articulated in R v Porter and the statutory requirement that the impairment must have precluded the accused from knowing the conduct was wrong. On sentence, the Court held that a sentence of 30 years' imprisonment (non-parole period of 23 years) for the murder of the applicant's mother was manifestly excessive where the applicant's delusional disorder was a necessary contributing factor to the offending, his anger was 'strongly linked' with the psychosis, and there were additional mitigating factors including age (65), no prior offending, poor health, and delay; the Court resentenced to 27 years with a 20-year non-parole period. The decision confirms that where a psychotic condition plays a dominant role in the development of the motive and decision to offend, the amelioration of sentence under Verdins principles must be 'marked or palpable' even where the offending is objectively very serious.
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