McHugh J. stated that judicial considerations need to be final and binding if the determinations of the Courts are to retain public confidence. Consequently, he said, the decisions of the Courts must be accepted as incontrovertibly correct unless set aside or quashed on appeal. He agreed with Lord Hailsbury in the English case of Reichel v. McGrath [1889]: "It would be a scandal to the administration of justice, if, the same question having been disposed of in one case, the litigant were to be permitted by changing the form of the proceedings to set up the same case again".
McHugh J. noted as a further consideration that the double jeopardy principle "conserves judicial resources and court facilities".
In Carroll the High Court referred to research and authorities from England and New Zealand.
The Law Commission of England and Wales recognised in its report on Double Jeopardy and Prosecution Appeals (2001. pdf, 360Kb), that finality is a value that finds its roots in personal autonomy. It serves to delineate the proper ambit of the State, and "respects the principle of limited government and the liberty of the subject".
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The New Zealand Law Commission said, in its recent report on the rule against double jeopardy, that the need to secure a conclusion is widely recognised, and that the status conferred by acquittal is important. The Commission quoted Lord Wilberforce in the English case of Ampthill Peerage [1977] AC 547 at 569:
Any determination of disputable fact may, the law recognises, be imperfect: the law aims at providing the best and safest solutions compatible with human fallibility and having reached that solution it closes the book. The law knows, and we all know, that sometimes fresh material may be found, which perhaps might lead to a different result, but in the interest of peace, certainty and security it prevents further enquiry. It is said that in doing this, the law is preferring justice to truth. That may be so: those values cannot always coincide. The law does its best to reduce the gap. But there are cases where the certainty of justice prevails over the possibility of truth … and these are cases where the law insists on finality.
Lord Wilberforce recognised that the rule against double jeopardy enhances the interest of peace, certainty and security by preventing further enquiry. The abolition or substantial modification of the doctrine of double jeopardy could lead to uncertainty, and a consequent corrosion of the community's confidence in the justice system.
The status of the rule
Double jeopardy provides protection to the citizen by preventing a citizen from being prosecuted again for an offence on which he or she may have been acquitted. Implicitly, it acts as a limit on State power by preventing prosecution as an instrument of tyranny. That this protection is guaranteed by the ICCPR is indicative of its importance to a just society.
The onus is upon the prosecution to present cases without delay, a principle the Courts have recognised as important in the finalisation of cases. The considerations of the protection of the citizen and fairness clearly outweigh the argument that a new trial is justified if fresh evidence is found which could result in a conviction.
Certainty and security enhance public confidence in the criminal justice system. In the words of Lord Hailsbury in Reichel, it would be a scandal if a litigant could present the same case by changing the form of the proceedings.
Limiting the power of the State protects the liberty of the citizen who is frequently powerless in contrast with its vast resources. Double jeopardy assists in redressing such an imbalance by preventing the unjustified harassment of the citizen by more than one prosecution. The status conferred by an acquittal would be seriously undermined by the abolition of double jeopardy.
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The vulnerability of the rule
But the common law is always subject to the will of parliament. Legislation can modify or negate any right or protection provided by the common law.
Current proposals to modify the rule against double jeopardy, despite its essential importance to our criminal justice system, only serve to highlight the absence in Australia of an entrenched guarantee of human rights. A parliament's power is subject to its constitution, although neither the Commonwealth nor any of the States and Territories carries any guarantees that would render invalid the abolition of the double jeopardy rule. It seems unlikely that the High Court would find, or even look for, an implied constitutional right to not be tried twice for the same offence.
An international remedy
However if the rule against double jeopardy is abolished or modified and a person is subject to a second prosecution for the same offence, there may be recourse to the ICCPR.
Australia is a voluntary party to the ICCPR, and is obliged to give effect to it. A breach by Australia - including by the States and Territories - would enable a person to complain to the Human Rights Committee, triggering an inquiry into the alleged breach. While the Committee only has recommendatory powers, and the Australian government rarely responds positively to the Committee's recommendations, it remains the last legal avenue for redressing a breach of human rights in Australia.
Being subject to double jeopardy would be such a breach, and if current reform proposals proceed, the Committee may well be hearing from Australia on such a matter in the near future.