Parity in sentencing is the principle that co-offenders should, all things equal, receive the same penalty.
However due to the nature of sentencing and the process of 'instinctive synthesis' whereby sentencers make a decision regarding all of the considerations that are relevant to sentencing, co-offenders will seldom receive alike sentences.
This is due to a large number of factors being taken into account in the sentencing process that may warrant a sentence which departs from that of the co-offender.
This makes the application of the parity principle unpredictable.
The Parity Principle
The principle of parity demands that there be no disparity between the sentences of co-offenders so as to give rise to a justifiable sense of grievance.
It demands "the treatment of like cases alike, and different cases differently": Green v The Queen (2011) 244 CLR 462, at .
To avoid an unjustifiable sense of grievance between the sentences imposed upon co-offenders party to the same criminal conduct or criminal enterprises, it is imperative for judicial officers to undertake a rigid assessment of all that is "required or permitted to be taken into account by the court under s 21A(1)": Green at .
How is the Party Principle applied ?
Should the persons be involved in the same criminal conduct or criminal enterprise, however, and are charged with the same offence, it is imperative to note that the parity principle is not confined in this respect and may still apply.
However, there do exist limitations to the application of the principle of parity to co-offenders who have been charged with different offences. Campbell J in Green at  acknowledges the limitations highlighted in Jimmy v R (2010) 77 NSWLR 540:
"There are significant limitations, however, on reducing a sentence on the basis of that of a co-offender who has committed a different crime. At least some limits the use of the parity principle in such a case are:
- It cannot overcome those differences in sentence that arise from a prosecutorial decision about whether to charge a person at all, or with what crime to charge them.
- If it is used to compare the sentences of participants in the same criminal enterprise who have been charged with different crimes, there can be significant practical difficulties. Those practical difficulties become greater the greater the difference between the crimes charged becomes, and can become so great that in the circumstances of a particular case a judge cannot apply it, or cannot see that there is any justifiable sense of grievance arising from the discrepancy.
- It cannot overcome differences in sentencing that arise from one of the co-offenders having been given a sentence that is unjustifiably low.
- There are particular difficulties in an applicant succeeding in a disparity argument where the disparity is said to arise by comparison with the sentence imposed on a co-offender who has been charged with an offence that is less serious that an offender."
Best Practice in Sentencing
As a matter of practice, it would be prudent to ensure that all co-offenders are sentenced by the same sentencing judicial officer to ensure that there is not disparity between the sentences: Dwayhi v R (2011) 205 A Crim R 274 at - and Postiglione v The Queen (1997) 189 CLR 295.
The allowance of the same judicial officer to sentence the co-offenders permits the judicial officer to "consider the interrelationship between the objective and subjective features of the offenders in an overarching way": Usher v R  NSWCCA 276 at .
Should the co-offenders be sentenced by different judicial offenders, it is imperative to note that the judicial officer is not necessarily bound by the findings made by another judicial officer in respect of another co-offender: Baquiran v R  NSWCCA 221.
Should the judicial officer depart from the sentence imposed upon a co-offender, the judicial officer must ensure that they differentiate between the moral culpability amongst the co-offenders by reference to their contribution to the joint criminal enterprise: R v JW (2010) 77 NSWLR 7 at .
It has been held in R v Wright  NSWCCA 3 at  that any departure identified by the judicial officer from the sentence imposed upon a co-offender as a result of an identified differentiation in the moral culpability amongst the moral culpability of the co-offender must not be too great because their ultimately existed a common purpose to commit the offence by the co-offenders and the judicial officer must acknowledge the offender's participation in the joint enterprise.
Justifiable sense of grievance ?
Where there exists a discrepancy or put more simply, an inconsistency in the sentencing of co-offenders, the conclusion must be drawn that there exists a degree of disparity in the sentencing of the co-offenders giving rise to a justifiable sense of grievance.
Of importance here is the decision of Lowe v The Queen (1984) 154 CLR 606 at  where Dawson J states as follows:
"There is no rule of law which requires co-offenders to be given the same sentence for the same offence even if no distinction can be drawn between them. Obviously, where the circumstances of each offender or his involvement in the offence are different then the different sentences may be called for but justice should be even-handed and it has come to be recognised both here and in England that any difference between the sentences imposed upon co-offenders for the same offence ought not to be such as to give rise to a justifiable sense of grievance on the part of the offender with the heavier sentence or to give rise to the appearance that justice has not been done".
The test of an unjustifiable sense of grievance is an objective one reliant upon the circumstances of the offending conduct and moral culpability of the offender.
More specifically, the court must determine whether the asserted disparity is "gross, marked or glaring": Tan v R  NSWCCA 96 at .
It has been emphasised that a grievance will not arise where the court deems that there exists no acceptable basis for substituting a lesser sentence for one which is appropriate so long as it is appropriate to the circumstances of the case: Lowe at .
Whilst in such circumstances the appellant may be left with a grievance, the court will not interfere unless the disparity in sentence between the co-offenders evidences an error justifiable for appeal.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.