Victoria's Court of Appeal dismissed Cardinal Pell's appeal last month against convictions for five child sexual offences, by a 2 to 1 majority.

The background to this has been summarised, with unanimous jury verdicts of guilty on all counts being undisturbed on appeal.

However, the nature of our judicial system means some final questions remain about whether Cardinal Pell can appeal, how this may happen, and an appeal's prospects of success.

These are complex questions and it may assist to set out some of the key legal principles.

Why can Cardinal Pell appeal after losing in the Victorian Court of Appeal?

An appeal to the High Court of Australia is possible. However, there is no automatic right to appeal.

A convicted person must secure the High Court's permission to appeal, and several technical requirements are involved in obtaining this.

Justice Anne Ferguson, Justice Chris Maxwell and Justice Mark Weinberg heard George Pell's appeal against his child sex abuse convictions. ( Supplied: Supreme Court of Victoria )

How does a convicted person appeal to the High Court?

By filing an application for "special leave" to appeal within 28 days of the prior decision.

If the High Court grants this leave, a notice of appeal must be filed within 14 days and the appeal will later be heard in full. If special leave is denied, the matter is over.

What does the High Court take into account?

The High Court does not lightly give leave to appeal.

It must apply statutory criteria in this decision, considering:

if the proceedings involve a question of legal principle that is either of public importance (of general application or otherwise), or regarding which there is a need to resolve differences of opinion between courts, or within one court; and

if the proceedings involve a question of legal principle that is either of public importance (of general application or otherwise), or regarding which there is a need to resolve differences of opinion between courts, or within one court; and if the interests of the administration of justice, either generally or in the particular case, require it to consider the earlier judgment. The Court will also consider whether an appeal has a reasonable prospect of success.

Statistically, what are Cardinal Pell's chances?

Not that great. Annual reports show most special leave applications are denied.

A 2019 study found only 23 out of 161 applications in the criminal jurisdiction were successful over two years (14.29 per cent).

A scan of recent applications for special leave to appeal based on the unreasonable verdict argument in child sexual offences show they are nearly always were dismissed (for example, O'Brien) with very rare exceptions (for example, GAX, where the Court gave leave on the basis the law had not been appropriately applied, which created a miscarriage of justice)".

On balance, it is probably unlikely the High Court will grant an appeal, but here matters become complex and difficult to predict.

The first basis for granting leave — a question of legal principle requiring resolution — is not clearly evident here.

The tests regarding unreasonableness of jury verdicts are settled and coherent, including how to determine whether a verdict is unreasonable (the open to the jury test), and the role of the court in implementing the test (independently assessing the whole of the evidence to determine whether it was so open to the jury).

The majority judgment by Ferguson CJ and Maxwell P carefully and accurately described the relevant legal principles, which have been regularly stated and applied elsewhere.

Weinberg J's dissent did not dispute the essence of these tests. The court split in applying the tests does not demonstrate a question of legal principle.

What might Cardinal Pell's defence team argue?

They may focus on the second basis for leave: the interests of justice.

They may rely on aspects of Weinberg J's dissent, and claim a wrongful conviction, amounting to a miscarriage of justice.

The cornerstone of Weinberg J's dissent was his interpretation that the "opportunity" testimony — including statements by two witnesses about being with Pell at relevant times — created a "reasonable possibility" of what amounted to an alibi for the first four offences.

Weinberg J had "a genuine doubt" about Pell's guilt, thought there was a "significant possibility" the offences had not been committed, and inferred the jury ought to have had this doubt.

Such arguments will likely meet robust opposition.

The majority judges disagreed with Weinberg J, finding through careful and cogent reasoning the testimony did not confirm these witnesses' presence with Pell, and instead concluding the evidence confirmed the complainant's account was possible.

They were not persuaded the jury must have had a reasonable doubt on this or any other basis.

They also found aspects of the complainant's account constituted independent corroborative evidence.

As well, the defence had not argued acquittal must follow if the opportunity evidence created only a "reasonable possibility" of impossibility.

Less than 15 per cent of special leave applications to the High Court were successful ( ABC News: Gregory Nelson )

Most importantly, an appellate judge's own doubt alone is simply not the legal test for a verdict's unreasonableness, and does not automatically mean the jury must have had this doubt.

The opportunity testimony may have entitled the jury to have a doubt, but this is not enough.

That testimony, or some other aspect of the evidence, must have been sufficient to demonstrate the guilty verdict was not open to the jury on the whole of the evidence, and the dissenting judgment did not compellingly identify such evidence.

The High Court is highly unlikely to grant leave simply due to an alternative interpretation of the facts.

The majority judgment appears to have thoroughly undertaken its independent assessment of the evidence concerning its sufficiency and quality, to weigh the evidence for the purpose of answering the question of whether it was open to the jury to be satisfied beyond reasonable doubt of the accused's guilt.

This will make it difficult for the applicant to obtain leave, or succeed on appeal

What happens if the High Court grants leave to appeal?

An appeal will be heard several months later, with judgment delivered several months after that.

The court can rule in the respondent's favour and dismiss the appeal, and all appeals are then exhausted.

Alternatively, it can grant a new trial, or reverse or modify the prior judgment.

Ben Mathews is a professor in the School of Law at Queensland University of Technology in Brisbane. He was Professorial Fellow to the Royal Commission Into Institutional Responses to Child Sexual Abuse from 2015-17.

Editor's note: On Tuesday April 7, 2020, the High Court in a unanimous decision upheld Cardinal Pell's appeal and quashed his convictions on all five charges.