Lawyers' reasoning is not always easy for non-lawyers to grasp. It is obvious to criminal lawyers that if at sentencing a mitigating factor is absent, the offender is not being punished additionally because of that absence.
Today the High Court of Australia addressed this sort of logic in Republic of Croatia v Snedden  HCA 14. Mr Snedden had resisted extradition to Croatia by claiming as an extradition objection that if tried in Croatia he would be subject to additional punishment because of his political beliefs. Service in the Croatian army, he claimed, was treated as a mitigating factor in relation to the relevant offences, and since he had served in the Serbian army he would be subject to additional punishment.
Heydon J pointed out that there was no factual substratum for Mr Snedden's claim. There was an absence of proof of the practice of Croatian courts in the relevant respect (83). So it was unnecessary to consider the issues that would arise if there was such proof.
The other members of the Court did address those issues. French CJ highlighted the absence of a causal connection between the absence of the mitigating factor and the claimed relevance of Mr Snedden's political beliefs to the punishment he could face (24). Just because the Croatian court would not be able to mitigate penalty on the basis of service in the Croatian army, did not mean that the court would be considering what Mr Snedden's political beliefs might have been.
French CJ did not dissent from the general proposition in the joint judgment (Gummow, Hayne, Crennan, Kiefel and Bell JJ at 79) that absence of a mitigating factor does not mean that an offender is being punished for its absence:
"79 A rational sentencing system will accommodate mitigating factors arising from the circumstances of the offender and the offence. In that context, ineligibility for a mitigating factor at the sentencing stage of a trial cannot be said to be punishment. Conceptually, the absence of a mitigating factor does not constitute or attract punishment. In particular, the absence of a mitigating factor is not an aggravating factor. Thus, while a plea of guilty is a mitigating factor, a plea of not guilty is not an aggravating factor."
There was no evidence here that absence of the mitigating factor would be treated as a punishment.
By way of comment, one might say it is all relative. If there were two accused persons being sentenced, only one of whom could rely on the mitigating factor (for example a plea of guilty), then from the point of view of the accused who pleaded not guilty, he is receiving a heavier punishment than the other, and the only reason – from his own point of view – is that he pleaded not guilty. He does not see the big picture. It is only when the frame of reference is changed to that of a third person (a spectator or the judge) that the wider theory of sentencing is apparent.
Courts insist on the "big picture" frame of reference because there are sound policy reasons for recognising mitigating factors. That is sensible and inevitable. Getting clients to understand the justice of the reasoning is an entirely different problem.