Edit: Another good discussion of Markarian‘s case can be found in the Newcastle Law Review. It was written by Ross Abbs a couple of years and approaches the case from a variety of angles.
The irrelevance (or, perhaps more properly, the lack of utility) of but for sentences was affirmed in Dutton v The Queen  VSCA 287 [Whelan AJA at 38].
The detailed and sometimes contradictory line of authority on this issue is navigated in Saab v The Queen  VSCA 165. Buchanan, Weinberg and Mandie JJA simultaneously supported and overruled Burke when they stated together [at 58]:
We think that the line of authority holding that a s 6AAA statement is generally not to be taken to exhibit error should be followed.
The principal obstacle to a determination that the notional sentence stated pursuant to s 6AAA can reveal specific error lies in the fact that sentences are the product of a process of instinctive synthesis. Judges do not fix sentences by adding to and subtracting from a starting point periods of time they attribute to particular sentencing factors: Wong v R (2001) 207 CLR 584. In order to comply with s 6AAA, a sentencing judge is required to guess the part played by one of a number of conflicting and contradictory elements in a synthesis of all the elements and ascribe a number to that element. As Gaudron, Gummow and Hayne JJ said in Wong v The Queen:
So long as a sentencing judge must, or may, take account of all of the circumstances of the offence and the offender, to single out some of those considerations and attribute specific numerical or proportionate value to
some features, distorts the already difficult balancing exercise which the judge must perform.
It may be thought that there is more chance of an error in this artificial, contrived exercise than in the original synthesis.
The notion that error may lie in placing too great or too little weight on a particular sentencing factor invites an analysis which we consider is irrelevant. A particular sentencing judge may have given what another judge may think is too little weight to a plea of guilty but perhaps may have given too much weight to a different mitigating factor. We think it profitless to criticise a sentencing judge’s guess as to the precise part played by one element if the result of the synthesis is a sentence which is within a range of appropriate sentences.
That is not to say that a s 6AAA statement can never reveal error. In a particular case, where an offender’s conduct in pleading guilty, the contrition the plea exhibits, and the utilitarian value of the plea all call for a substantial discount, the s 6AAA statement may reveal that the plea was effectively ignored, so that it may be concluded that the sentencing judge failed to have any regard to a relevant factor in exercising his discretion. The statement may amount to an expression in numerical terms of a view that, if put into words, would betoken specific error. Such a case will be rare.
The judgment is a careful study of the conflicting authority, and deserves careful reading. But, trying to boil this equivocacy into a definite statement – a but for statement doesn’t provide grounds for appeal, even if it’s wrong. But it will, if it provides an insight into the sentencing judge’s thinking, that demonstrates appellable error. How does one tell the difference? Who knows.
Section 6AAA of the Sentencing Act 1991 has been around for a while now. It applies when a sentencing court imprisons an offender or fines them 10 or more penalty units. If the Court imposes a less severe penalty than it otherwise would have because the defendant pleaded guilty, it must state what that penalty would have been but for the guilty plea.
The provision was inserted into the Sentencing Act 1991 in 2007 after recommendations from the Sentencing Advisory Council in its Sentence Indication and Specified Sentence Discounts — Final Report. The Council said one of the aims of the legislative change was to encourage more offenders to plead guilty, and at an earlier stage in proceedings. It is also fair to say that some in the judiciary aren’t comfortable with isolating and placing a figure on one particular consideration when arriving at an appropriate sentence. It has been suggested that doing so goes against the traditional sentencing concept of instinctive synthesis. (The High Court recently affirmed instinctive synthesis as the proper approach to sentencing, in Markarian v The Queen  HCA 25; (2005) 215 ALR 213.)
In The Queen v Burke  VSCA 60, the Court of Appeal dealt swiftly with a ground of appeal that tried to rely on the ‘but for’ indication given by the sentencing judge.
Vickery AJA (Redlich JA and Maxwell ACJ agreeing) said [at 29]:
29 As noted earlier, his Honour said:
but for your plea, I would have considered that an appropriate term of imprisonment would be four years with a non-parole period of two and a half years.
Ground 2 contended that the ‘notional’ sentence of four years was manifestly excessive. This in turn was said to have ‘infected’ the sentence which was actually imposed.
30 The submission is misconceived. The ‘notional’ sentence announced in accordance with s 6AAA is not part of the sentence imposed. No appeal lies in respect of the notional sentence. As s 567(d) of the Crimes Act makes perfectly clear, the appeal court hears an appeal against ‘the sentence passed’. Accordingly, the contention in Ground 2 – that the ‘notional sentence’ would have been manifestly excessive – is unintelligible in this sphere of discourse. It cannot constitute a ground for appeal.
31 The ground of manifest excess falls to be considered in relation to – and only to – the sentence actually imposed. A complaint about the sentence discount or the notional sentence identified in the s 6AAA statement is a complaint about the weight attributed to one particular sentencing consideration. As with any argument about weight, the question for the appeal court is whether, taking into account all the relevant sentencing considerations, the sentence imposed was within range.
The Court found that the sentence which had been imposed disclosed no error. Consequently, the appeal was dismissed.
On a related note, the other day I came across a speech that Royce Miller QC gave at an Australian Institute of Criminology conference back in 1996 when he was the Queensland Director of Public Prosecutions. Over a 40 year career he served the interests of justice first as a barrister, then as Crown Prosecutor, Public Defender, District Court judge and finally, DPP. The paper is called Pleading Guilty: Why, How and When, and offers a refreshingly candid perspective on sentencing.