The appellant was granted special leave to appeal in this case because he contended that the key question in the case was whether "two-tier sentencing" in contrast to "instinctive synthesis" is the correct approach to sentencing. In this case, the Court of Criminal Appeal applied the "two-tier" approach. It erred in doing so.
By two-tier sentencing, I mean the method of sentencing by which a judge first determines a sentence by reference to the "objective circumstances" of the case. This is the first tier of the process. The judge then increases or reduces this hypothetical sentence incrementally or decrementally by reference to other factors, usually, but not always, personal to the accused. This is the second tier. By instinctive synthesis, I mean the method of sentencing by which the judge identifies all the factors that are relevant to the sentence, discusses their significance and then makes a value judgment as to what is the appropriate sentence given all the factors of the case. Only at the end of the process does the judge determine the sentence.
The two-tier sentencer contends that using the instinctive synthesis is inimical to the judicial process and is an exercise of arbitrary judicial power, unchecked by the giving of reasons. The two-tier sentencer claims, as Hulme J did in this case, that, where the sentence is the result of an instinctive synthesis, it makes one "wonder whether figures have not just been plucked out of the air". The instinctive synthesiser, on the other hand, contends that the two-tier sentencer mistakes an illusion of exactitude for the reality of sentencing because there is no method of sequential arithmetical reasoning that produces the correct sentence for any case. A sentence can only be the product of human judgment, based on all the facts of the case, the judge's experience , the data derived from comparable sentences and the guidelines and principles authoritatively laid down in statutes and authoritative judgments. The instinctive synthesiser asserts that sentencing is not an exercise in linear reasoning because the result of each step in the process is not the logical foundation for the next step in the process. Nor in practice can it be an exercise in multiple regression where one starts with particular coefficients and adds to or subtracts from their result by changing the weighting of each variable as new variables are added to the process. The circumstances of criminal cases are so various that they cannot be the subject of mathematical equations. Sociological variables do not easily lend themselves to mathematisation. Hence, when judges embark on a process that seeks to adjust incrementally or decrementally a hypothetical sentence, "they but illustrate the way in which the human mind tries, and vainly tries, to give to a particular subject matter a higher degree of definition than it will admit", as Lord Porter said in another context.
In AB v The Queen, I gave my reasons for preferring the instinctive synthesis approach. In my view, the judge who purports to compile a benchmark sentence as a starting point inevitably gives undue - even decisive - weight to some only of the factors in the case. Furthermore, the judge falls into the error of determining that notional sentence by reference to a hypothetical crime derived from some only of the circumstances of the case. Instead of sentencing this accused for his or her criminality, the judge sentences the person for another crime and adjusts the notional sentence by reference to factors that are additional to the objective circumstances. Indeed, there are some offences - manslaughter is an example - where an attempt to fix a first-tier sentence by reference to the objective circumstances is meaningless. How can a judge possibly fix a first-tier or any sentence for the mother who has killed her newborn baby without taking into account her personal circumstances?
Moreover, by concentrating on the objective circumstances of a crime, the judge is giving effect, and ultimately greater weight, to the retributive or deterrent theory of sentencing. Indeed, the judgment of the Court of Criminal Appeal in this case makes it clear that the Court thought that the issues of retribution and deterrence were the dominant issues in the case. Consciously or unconsciously, the judge who commences with a notional sentence downplays the importance of mitigation, reformation and rehabilitation in the sentencing process. Cognitive psychology has long emphasised the difficulty that the human mind has in giving correct weightings to each of a number of variables. In particular, people frequently fail to distinguish between the strength of evidence and its relative weight in determining the outcome or prediction. As Griffin and Tversky have pointed out:
"The extensive experimental literature on judgment under uncertainty indicates that people do not combine strength and weight in accord with the rules of probability and statistics."
The tendency of the mind is to seize on one or two variables - usually those with which the decision-maker is most familiar or which seem most cogent - and give that variable or those variables undue weight. Overconfidence - but sometimes underconfidence - in the significance of factors or the accuracy of the assessment is very common. The tendency to err must increase when particular circumstances are selected as the starting point for the decision and further factors are allowed to modify the starting point.
One fact that critics of the instinctive synthesis approach do not face up to - assuming they are aware of it - is that the first tier of the two-tier approach - unless it is the maximum sentence - is itself derived by an instinctive synthesis of the "objective circumstances" of the case. Or on another view of the two-tier approach, the first-tier sentence is the product of a value judgment that is proportionate to the offence. But as the Victorian Court of Criminal Appeal said in R v Young :
"What is a sentence proportionate to an offence is a matter of discretion and there must in most cases be a range of sentences open to a sentencing judge which are proportionate to the offence. There cannot be said to be a sentence which is the proportionate sentence
... Thus to attempt to fix a proportionate sentence before fixing the sentence to be imposed will only multiply the possibilities of error. Upon what facts is the proportionate sentence to be fixed?"
(Emphasis in original.)
Analysing the process involved in two-tier sentencing reveals that its appearance of objectivity and unfolding reason is illusory. Whether the starting point is a sentence derived from the objective circumstances or a sentence proportionate to the offence, the correctness of the sentence always depends on the correctness of the value judgment involved in assessing the first-tier sentence. But even if the judge can correctly assess the first-tier sentence, the judge must still correctly assess the quantum of the increment or decrement for each factor in the process. With great respect to those who think the contrary, it would require a judge to have the statistical genius and mental agility of a Carl Friedrich Gauss to arrive at the correct sentence using these methods. As Gaudron, Gummow and Hayne JJ pointed out in Wong v The Queen, mathematical increments and decrements to some pre-determined notional sentence are "apt to give rise to error".[35]