25 In any event, the settled law in relation to an offender's mental illness does not require such an exercise to be undertaken. The authorities bearing upon this question have been helpfully summarised by Simpson J in Benitez v R (2006) 160 A Crim R 166 ; [2006] NSWCCA 21 at [36]-[38] :-
For mental illness or a psychiatric condition to be relevant to sentencing it is not necessary that it be the cause of the commission of the crime. Indeed, authorities suggest that it is not necessary that it be a cause of the crime. I refer to the decision of this court in R v Fahda [1999] NSWCCA 267 at [40] - [48]. There reference was made to a number of authorities of which the following are, on this issue, relevant. In R v Letteri (unreported, NSWCCA, 18 March 1992), Badgery-Parker J. said:
In each of those cases [which he had, in the preceding paragraph, cited], it appears that the mental illness or retardation was a factor inducing the commission of the offence but that is not a necessary condition of the application of the principle. . (Emphasis added)
In R v Engert (1995) 84 A Crim R 67 Gleeson CJ said:
In truth, however, … the question of the relationship, if any, between the mental disorder and the commission of the offence, goes to the circumstances of the individual case to be taken into account in the application of the relevant principles. The existence of such a causal relationship in a particular case does not automatically produce the result that the offender will receive a lesser sentence, any more than the absence of such a causal connection produces the automatic result that an offender will not receive a lesser sentence in a particular case. For example, the existence of a causal connection between the mental disorder and the offence might reduce the importance of general deterrence, and increase the importance of particular deterrence or of the need to protect the public. By the same token, there may be a case in which there is an absence of connection between the mental disorder and the commission of the offence for which a person is being sentenced, but the mental disorder may be very important to considerations of rehabilitation, or the need for treatment outside the prison system .(Emphasis added)
A mental disorder such as the applicant's depression was identified by Gleeson CJ in Engert as being part of the circumstances of the individual case. Generally speaking, the well-known authorities indicate that mental disorder may be relevant to the assessment of the offender's culpability and to the level to which it is appropriate to give greater or lesser emphasis to principles of general or specific deterrence: see also R v Scognamiglio (1991) 56 A Crim R 81 ; Letteri ; R v Champion (1992) 64 A Crim R 244 ; R v Wright (1997) 93 A Crim R 48.
26 It is also relevant in the present context to refer to what was said by Wood CJ at CL in R v Matthews [2004] NSWCCA 112, namely that ;-
[A]s was made clear in R v Elchami NSWCCA 15 December 1995, and also in R v Wright (1997) 93 A Crim R 48, and in R v Bus NSWCCA 3 November 1995, these principles have a lesser relevance for an offender with a low level of intellectual functioning, or a developmental disorder, where, notwithstanding that incapacity or disorder, he or she has a clear knowledge of what is being done, an awareness of its wrongness, and a capacity for impulse control.
27 It may, of course, be helpful to undertake an assessment of the extent to which an offender's mental illness has contributed to criminal behaviour, whether that be by way of disinhibiting the offender, removing or impairing the capacity for judgment or, at one extreme, inducing the commission of offences (see Wood CJ at CL in Matthews at [27]).
28 In the absence of any evidence from the applicant's legal representative before the sentencing Judge, I am not prepared to infer that there was any incompetence on his part. There was more than sufficient psychiatric evidence to support the finding that his Honour made. Further clarification of the extent of Dr O'Sullivan's contact with the applicant may have been desirable, but it was far from a mark of incompetence.