"His Honour said that he would allow a 'significant credit' for that fact. In imposing sentence his Honour went on to say that but for the early plea of guilty and other matters of mitigation, he would have sentenced the applicant to a term of 18 years imprisonment but, having regard to those matters, he reduced the sentence to a term of 14 years imprisonment. The applicant calculates that that is a discount of just over 22 per cent. Relying upon decisions of this Court, particularly Miles v The Queen (1997) 17 WAR 518, the submission is made that it is common for a discount for an early plea to range between 25 per cent and 35 per cent and if the 22 per cent includes other matters having a mitigatory tendency, it follows, so the argument runs, that the discount must be seen to be manifestly inadequate and the sentence should be held to be manifestly excessive on that ground alone.
To my mind, the argument fails for at least two reasons. In the first place, the process of taking a proportion expressed as a percentage of a notional starting point, even one articulated by the sentencing Judge, and endeavouring to demonstrate that the sentence imposed is manifestly excessive having regard to the percentage figure, is an illusory process because the so-called 'starting point' is not the sentence, the adequacy or proportionality of which the appellate court is required to measure so that the appeal will succeed if it can be demonstrated that the exercise of sentencing discretion has miscarried because the sentence finally imposed is manifestly excessive.
Secondly, in my opinion, although this Court has observed from time to time, including in Miles at 521, that the substantial discount required to be given by the law (Sentencing Act 1995 (WA) s 8(2)) has in fact been able to be seen to be in the order of from 20 to 25 per cent up to 30 to 35 per cent, depending upon the circumstances, it has never been suggested, and in my respectful opinion rightly so, that it is an appropriate way for an appellate court to consider the adequacy of a sentence, to allocate periods of time or percentage points applied to a starting point for the purpose of deciding whether the sentence imposed is manifestly excessive or inadequate: see also Cameron v The Queen [2002] WASCA 81 per Miller J, with whom Murray and Steytler JJ agreed, at pars [16] - [19].
That is because, to put it shortly, as did the majority of the High Court in Pearce v The Queen (1998) 194 CLR 610 at 624 [46], 'Sentencing is not a process that leads to a single correct answer arrived at by some process admitting of mathematical precision.' The attempt to measure the size of the discount diverts the appellate court from the essential task of determining whether the sentencing discretion has miscarried because the Judge has made some error of principle or because, even though error is not particularly identifiable, it is demonstrated because the final result is manifestly excessive or inadequate. In my opinion, ground 1 is misconceived."