If the police and the tribunal have their way, there will be a different class of prisoner in Northern jails over the next few months with the potential imprisonment of a journalist, Suzanne Breen, and a senior politician, Ian Paisley jnr.

There is, of course, no general immunity for either journalists or politicians, and there are some in both professions over the years whom many think could well have been put behind bars — but not for protecting their sources.

Suzanne Breen's difficulties arise from an article in the Sunday Tribune which reported having received information that the Real IRA was claiming responsibility for the murder of two soldiers at Massereene Barracks in Antrim, and threatening further action in Britain.

The PSNI demanded that she tell them the source of her information, which, like any self-respecting journalist, she refused to do. The PSNI chief constable then sought a court order requiring her to hand over notes and records, laptop and mobile, at which she again refused. One would imagine, however, that the police had their own sources which they, too, were unwilling to disclose, for much the same reasons.

Ian Paisley jnr is in trouble with the tribunal that is investigating the INLA murder in the Maze Prison, in December 1997, of the loyalist leader Billy Wright.

Billy Wright's father approached Mr Paisley in his capacity as a MLA, for help in getting a full public inquiry into the murky circumstances of his son's death.

Mr Paisley, in a letter, told him that he had been informed by a senior prison officer that documents and records for the relevant period had been officially destroyed.

The tribunal demanded that Mr Paisley tell them the name of his prison officer informant, and, when he refused, served him with a writ requiring him to do so, at the risk of imprisonment.

While the Assembly is not a parliament, it is surprising that the Assembly Speaker should not take issue with the intrusion which allowed an elected member to be accosted by a summons-server within the precincts.

Ian Paisley jnr's case was paralleled in the South by the demand of the Morris Tribunal that Senator Jim Higgins and Brendan Howlin TD disclose the source of their information on garda misconduct in Donegal which led to the setting up of the tribunal itself.

They too, refused, very properly most people would think, and but for the informant outing himself, the issue would have been tested in the courts in a clash between tribunal and Oireachtas.

It is relevant, too, that the Supreme Court is about to adjudicate on the issue of the protection of sources in a case arising from the Mahon Tribunal, where journalists are pleading a public interest in the protection of sources.

It is, of course, in the public interest that murderers should be caught, convicted and punished. Tribunals of inquiry are set up under the law to investigate corruption and to establish the facts.

It cannot be in the public interest that they should be wilfully obstructed in the search of truth. But it would not be in the public interest of the discovery of truth, either, that journalists should be prevented from doing their job.

Investigative journalism depends, very often, on information, or hints or leads given in confidence by insiders.

If the sources were to remain silent for fear of disclosure, much would remain hidden that should be disclosed in the public interest, and corruption, which should be exposed, would continue to thrive.

Similarly, members of parliament or Assembly members, if they are to be able to defend the legitimate interests of their constituents in exposing official maladministration or worse, would be severely handicapped if they could not claim some degree of privilege.

There is no law protecting journalists or politicians in these cases.

Neither is there an absolute right to protect sources. In a case that a journalist had information that a serious crime was about to be committed, or a terrorist bomb, few outside the profession would argue a right to silence.

It all comes down then to a question of proportionality — which is presumably what the courts will decide.

The police were within their rights to ask Suzanne Breen for disclosure, and by any standards of journalistic behaviour, she had no choice but to refuse. Her case is complicated by the hearing of the police application in confidence — which the House of Lords has criticised in a terrorist-related case in Britain — and by the fact that her life has been threatened by the Real IRA.

In Mr Paisley's case, there is already information in the public domain, in the published memoir of William McKee, who was duty governor in the Maze when Wright was murdered, where he describes his feelings at the news that the prison service had destroyed much of the material required by the inquiry.

Mr Paisley, providentially, is not under a death threat, and imprisonment would, if anything, enhance his standing as a politician — it did his father no harm 50 years ago.

However, it would be shameful, and indeed against the public interest, if it came to that in either case. Both politician and journalist in these cases deserve public support, and the indulgence of the courts.