29 In Kerr the appellant was convicted at trial of aggravated robbery (involving the use of corporal violence), an offence that carries a maximum of 20 years' imprisonment. He was sentenced to a term of 13 ½ years' imprisonment. A co-offender was charged with robbery simpliciter contrary to s 94, an offence that carries a maximum of 14 years' imprisonment. The co-offender pleaded guilty and was dealt with by an ordered to perform 500 hours community service. The trial Judge accepted the Crown Prosecutor's submission that "no issue of parity" arose. In this Court, Miles AJ (with whose judgment the other members of the Court agreed) said this:
[13] However the principle of parity in sentencing, or rather policy behind it, was not so easily dismissed, in my view. The policy behind the principle is not to be avoided by the prosecuting authority simply charging co-operative offenders with less serious offences. The whole of the circumstances need to be examined.
[14] Clearly neither of the two was treated as a co-offender but at the same time each was implicated in the events which gave rise to the aggravated robbery.
[15] There are two aspects to the principles. Like has to be and may only be compared with like and imbalance must be enough to justify on objective analysis a sense of grievance on the part of the offender who complains of the heavier sentence: Postiglione v The Queen (1997) 189 CLR 295. As to the first aspect, the principle is difficult to apply in the present case since neither of the two co-offenders was charged with the offence of aggravated robbery. It may have been that the facts did not support that charge, at least against Tickner, although it is noteworthy that Tickner received the suspended prison sentence, having remained in the vehicle and driving the other two from the scene. This was a sterner penalty than that received by Oliver who was ordered to perform community service, having accompanied the applicant into the house disguised in a balaclava and wielding the cricket bat. The charging of robbery simpliciter against Oliver appears explicable on the basis of his cooperation with the authorities rather than his actual participation in the events.
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[19] It is established that disparity so called can arise when a co-offender is sentenced after the aggrieved offender has been sentenced: Postiglione v The Queen . In such cases there can be no error on the part of the judge sentencing the offender later aggrieved: Lowe v The Queen (1984) 154 CLR 606 at 610 - 611. It is also recognised that the parity principle is of wide application and is not to be applied or withheld in a technical or pedantic way. It is indeed part of or a reflection of the wider principle that consistency in sentencing by the courts overall is to be aimed at as desirable in the public interest. Perfect consistency is a goal that can never be reached because of the infinite variety of the circumstances of offences and offenders. However there is a danger that it may be compromised by the selection of differing charges so that one offender may be charged with a serious offence and given punishment at the top of an acceptable range for that offence, and a co-offender charged with another less serious offence and dealt with at the very bottom of the acceptable range for that other offence. There may be no impropriety in that course, which will often arise from negotiation between co-offenders and law enforcement authorities. Sometimes, however, and it is not necessary to put it higher than that, the result may have the appearance of injustice.