62 On 1 June 2010 Dr Dennis Lowe, ophthalmic surgeon and consultant neurologist, reported that the offender's capacity for critical judgment and insightful thinking was extremely limited. After referring to Professor Lance's finding in October 1994 that the offender suffers from a localised area of atrophy involving the anterior pole of the left temporal lobe, Dr Lowe expressed the opinion that damage to this area may result in behavioural changes. In this connection he noted the offender's reported history of mood swings and very poor temper control.
63 Having regard to the considered views of a range of clinicians over an extended period of years, I am compelled to the finding that the offender does have brain damage which impacts adversely on his mental and psychosocial functioning, and which increased the risk of him overreacting to the deceased when he presented at his door in the early hours of 3 October 2007 looking for drugs or money, or, because of his animosity towards the deceased, prevented him from controlling his aggression. In R v Hemsley [2004] NSWCCA 228 Sperling J set out the principles that fall to be considered when an offender who suffers a mental illness is to be sentenced:
"[33] Mental illness may be relevant … in three ways. First , where mental illness contributes to the commission of the offence in a material way, the offender's moral culpability may be reduced; there may not then be the same call for denunciation and the punishment warranted may accordingly be reduced: Henry at [254]; Jiminez [1999] NSWCCA 7 at [23]; Tsiaras [1996] 1 VR 398 at 400; Lauritsen (2000) 114 A Crim R 333 at [51]; Israil [2002] NSWCCA 255 at [23]; Pearson [2004] NSWCCA 129 at [43].
[34] Secondly , mental illness may render the offender an inappropriate vehicle for general deterrence and moderate that consideration: Pearce (NSWCCA, 1 November 1996, unreported); Engert (1995) 84 A Crim R 67 at 71 per Gleeson CJ; Letteri (NSWCCA, 18 March 1992, unreported); Israil at [22]; Pearson at [42].
[35] Thirdly , a custodial sentence may weigh more heavily on a mentally ill person: Tsiaras at 400; Jiminez at [25]; Israil at [26].
[36]A fourth , and countervailing, consideration may arise, namely, the level of danger which the offender presents to the community. That may sound in special deterrence; Israil at [24]."
64 While I am satisfied that this offender's brain damage and associated dysfunction operates to displace to a significant degree the need for the sentence to reflect the need for general deterrence, I am not persuaded, in the circumstances of this case, that it significantly diminishes the offender's moral culpability for the death of the deceased, or that his conduct does not call for denunciation. This is not only because his brain injury is one of a number of explanations, or possible explanations, identified by Dr Allnutt for his conduct in arming himself and stabbing the knife into the chest of the deceased, but the offender's behaviour before, immediately after, and then some days after the offence militate against allowing any relaxation of his moral culpability.
65 Dr Allnutt was ultimately of the view in his most recent report that it was reasonable to conclude that there were a number of elements active at the time of the death of the deceased, including the offender's inborn tendency to impulsive aggression, substance intoxication, depressive symptoms, an acrimonious relationship with the deceased and frontal lobe brain damage, which increased the offender's vulnerability to impulsive behaviour. Dr Lowe also identified these same factors as likely to have been active at the time of the offence. Not only do I consider this aspect of his opinion as outside his expertise, it would appear that he has simply restated Dr Allnutt's views without, as I have noted earlier, the offender being interviewed after he was convicted of murder by either specialist about the circumstances of the offending in light of the jury's verdict. I have already discounted the influence of the offender's drug use on the day of the killing as providing any explanation for, or context to, his offending, although on the basis of the history the offender gave to Dr Allnutt he had been both supplying and using drugs in considerable quantities for some months prior to October 2007. While this does not aggravate the offending, or bear on the question of his moral culpability for the deceased's murder, it does militate against his prospects of rehabilitation particularly given that his responsibility for the intentional killing of another man in 1986 was found to be diminished in part because of his chronic use of cannabis.