She said: ''Australians know … that too many children have suffered child abuse, but have also seen other adults let them down. They've not only had their trust betrayed by the abuser but other adults who could have acted to assist them have failed to do so.

''There have been too many revelations of adults who have averted their eyes from this evil. I believe in these circumstances that it's appropriate for there to be a national response through a royal commission.''

Some immediate questions come to mind. Who did the covering-up? How did they know about the abuse that was covered up? Was that covering-up criminal?

In the case of Catholic priests, of course, one channel of knowledge about child sex abuse was the confessional. This poses the evidentiary problem, and also a constitutional one.

Although the royal commission's act does not mention the confessional, it grants a general defence to witnesses who refuse to give evidence if they would have an excuse in a court of law, as priests do under the Commonwealth Evidence Act.

It means that the commission will be denied access to a significant source of information about the covering-up of child sexual abuse.

The exemption for religious confessions is unqualified, unlike exemptions for legal professional privilege, against self-incrimination or for journalists' sources.

The question is: should or could the exemption for the confessional be removed or qualified for this inquiry and in general?

Also, what should be the duty of a priest to whom a confession has been made about a serious crime, such as child sex abuse, or an intention to, say, commit murder? Would it be criminal not to tell police?

You could make a fair argument that reliance upon the shield of the confessional has been a significant part of the whole cover-up and that if the commission is to get anywhere it will have to have the shield removed.

However, the Parliament is unlikely to do that because of the electoral backlash. Nonetheless, the public interest in the exemption is worth questioning.

It is worth comparing the more limited exemptions given to communications between doctor and patient, lawyer and client, journalist and informant, and between spouse and spouse.

Each of those has a public-interest element. Patients might not seek treatment if they thought their condition might be exposed. Lawyers could not defend clients to their best without the full disclosure that is dependant on confidentiality, nor advise to settle or plead guilty where appropriate. Without confidence in a journalists' non-disclosure ethic, malfeasance might not be uncovered. It would be inimical to marriage to force spouses to give evidence against each other.

But there is no public interest or benefit in the unconditional protection of the disclosures at the confessional. If someone is discouraged from confessing to a priest, so what. A confession to a priest has no public benefit at all; the more so if the priest would never divulge the confession.

Indeed, there is a solid argument that giving the confessional protection against disclosure is against the public interest because the penitent might feel afterwards that there was no need to turn themselves in to police because ''God has forgiven them'' and they had been punished through whatever penance the priest ordered. True, a priest might encourage the penitent to turn themselves in, but it is of little comfort in a system in which the penitent can be confident the priest will never disclose.

In the case of the royal commission, there is a clear public interest in finding out what happened so measures can be taken to prevent recurrence of cover-ups by religious and other bodies. The cover-up is as bad as the original sexual abuse because the cover-up resulted in further abuse which would not have happened if offenders had been turned over to police when exposed.

The commission's job should be to find out who knew what and when. To do that effectively, it might well need to break the secrets of the confessional.

However, there are a couple of constitutional problems here should the federal government try to remove the confessional exemption.

The Constitution says, ''The Commonwealth shall not make any law for establishing any religion, or for imposing any religious observance, or for prohibiting the free exercise of any religion.''

The High Court has not yet struck down a law under this provision, though several have been challenged. The critical words are ''the free exercise of any religion''. Confession is central to the Catholic faith, as is the confidentiality of the confessional. Nonetheless, the court has interpreted the section narrowly. It has said religious belief is not a ground for failure to comply with the general law, such as military service and presumably any requirement to give evidence to an inquiry or a court.

The court did not allow Section 116 to get in the way of a regulation to disband and seize the assets of organisations (including religious ones) that were contrary to the war effort. In the 1943 Jehovah's Witnesses case the court rejected the Section 116 argument, but struck down the regulations because they went beyond the defence power.

A more difficult constitutional hurdle is the broader one. Under what head of constitutional power is the federal government acting in setting up this commission?

The Constitution gives the federal government defined powers which do not include the general criminal law or sexual abuse in particular.

It has an implied ''national purpose'' power which allows it to set up bodies like the CSIRO, museums and the like which might stretch to a national inquiry, but do not bet on it.

Bear in mind, the last Section 116 case ended in tears for the federal government, not because funding religious chaplains in schools was contrary to Section 116, but because the court held the federal government did not have an open-ended power to appropriate money for whatever purpose it thought fit - such as school chaplains - but was limited to spending money on the purposes of the federal government listed in the Constitution.

It would not surprise me if this royal commission were challenged on the same ground. The opposition and the Catholic Church might well give public support to the commission while hoping that someone else knocks it on the head.

The last thing the opposition wants in an election year is royal commission revelations about wrongdoing in the Catholic Church while it is headed by Australia's best-known Catholic.

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