This is the principal question to be addressed when the Disclosures Tribunal resumes public hearings today.

The issue was the focus of the first module of the tribunal last year, but now it moves into a different phase.

It’s a matter of immense importance. If the State colluded in any way to attack a citizen, particularly a member of An Garda Síochána, then serious accountability is required.

There have been instances when agents of the State may have been responsible for attacking citizens, usually where the target was suspected of serious criminal offences.

The McCabe case, however, is of a completely different order. His “offence” in the eyes of the State’s agents was to highlight how An Garda Síochána was not doings its job properly, and the lengths to which some were willing to go to cover up malpractice.

The issue to be opened today involves what happened behind the closed doors of a Commission of Investigation in May 2015.

The O’Higgins commission was set up on foot of a report in 2014 from senior counsel Sean Guerin.

He had investigated Sergeant McCabe’s allegations of malpractice in Cavan/Monaghan and found that a full commission would be required to properly investigate the matter.

Guerin went even further. “I have seen extensive documentation… which gives cause for concern about the personal and professional consequences for Sergeant McCabe of his having made the complaints examined in this report and other similar complaints.

“It is not for me to express any view of those matters, except to say that Sergeant McCabe’s experience calls for examination.”

Retired high court judge Kevin O’Higgins was appointed to chair the commission. He began work in December 2014 and commenced hearings on May 14, 2015. The Commission of Investigation model was introduced by then minister for justice Michael McDowell in 2004 to alleviate the huge costs of public tribunals.

By 2004, the planning and payments to politicians tribunals had been sitting for seven years — and both were only roughly halfway through their eventual life spans. There was, among the public, outrage at the cost as lawyers drank deeply at the tribunal trough.

McDowell’s model was to put an end to this expensive method of inquiry. It was to be conducted in private, alleviating the need for everybody to be lawyered up. Prior to O’Higgins, the model was used a number of times, most successfully in inquiries into clerical sexual abuse.

But just as holding inquiries behind closed doors cuts down on cost, it also cuts down on transparency. While inquiries are usually set up in response to public concerns, the public do not have sight of the inquiry in progress. Instead, just a report is published.

Notwithstanding this reservation, the model was regarded as a success. Then along came the O’Higgins commission and some of what went on behind the inquiry’s closed doors would eventually elicit major controversy.

The Disclosures Tribunal will examine whether there was an attempt in the early days of O’Higgins to portray McCabe as a man with a grudge. If the turbulent sergeant had a grudge, this would cast his complaints of malpractice in a different, darker light.

It would portray him as a man not intent on highlighting malpractice but one who was out to do harm to the reputation of the force. If successful, it would also call into immediate question the high opinion that the public, and much of the body politic, had of McCabe at the time.

The issue that was about to impinge on O’Higgins concerned an allegation by the daughter of a colleague of McCabe’s dating from 2006. The girl, now known as Ms D, claimed that McCabe had touched her inappropriately some eight years previously when she was six.

Some months before she made her complaint, McCabe had reported her father for indiscipline and he in turn had been demoted from his post.

The allegation was investigated and found to have no basis. However, the aspect of the case that was about to explode on the O’Higgins commission concerned how the DPP’s directions were regarded and dealt with.

On day two of the O’Higgins hearings, May 15, 2015, retired chief superintendent Colm Rooney was in the witness box. On foot of questioning about meetings with McCabe he told of a meeting which he dated to May/June 2007, he claimed McCabe had requested the meeting.

Mick Wallace recently gave the Dáil a summary of the evidence given by Rooney on that occasion.

“Chief superintendent Colm Rooney said Maurice was angry and vicious and wanted the DPP to overturn the directions from the Ms D file, not realising that Maurice had already seen them, agreed with them and wouldn’t be looking for them to be overturned.”

As Wallace pointed out, Rooney was unaware that McCabe knew the directions and that the directions could not have been more favourable to him. (McCabe had been furnished with the directions by the local state solicitor once they arrived back from the DPP).

McCabe gave evidence to this effect on the next day the commission sat. Why, then, was he described as being angry in Rooney’s original evidence?

Rooney was recalled to respond. At this point, he was not as emphatic as he was originally about McCabe’s emotional state at the meeting. There was a reference to an interpretation of McCabe’s anger through his body language.

Rooney’s evidence on the issue, any inconsistencies and any possible explanation of why he may have provided an apparent inaccurate portrayal of McCabe in his original evidence will all be examined by the tribunal.

While Rooney was giving evidence on the first occasion, another meeting was introduced by counsel for the garda commissioner, Colm Smyth. He said there would be evidence McCabe expressed a grudge at the second meeting, which occurred in Mullingar in August 2008, associated with the DPP’s directions in the Ms D case.

The meeting was between McCabe and two other officers, a superintendent and a sergeant. McCabe’s counsel Michael McDowell said that his client was being ambushed. He demanded some basis on which this allegation was to be introduced.

The following Monday, O’Higgins and McCabe’s legal team were furnished with a document laying out how McCabe expressed this grudge. The document was prepared by the chief state solicitor’s office, which in turn comes under the aegis of the attorney general.

The five-page document went through a sequence of events, including the meeting with Rooney and leading up to the meeting in Mullingar. It stated that at Mullingar, Sgt McCabe conveyed “that the only reason he made a complaint against Superintendent Clancy (McCabe’s district officer) was to force him to allow Sgt McCabe to have the full details of the DPP directions conveyed to him.”

Again, this ignored that McCabe had possession of the DPP’s directions. But in any event, McCabe was adamant that he never said any such thing, he never expressed any grudge as laid out in the chief state solicitor’s document. And he could prove it.

He had recorded the meeting in question at a time when he had come to believe he couldn’t trust anybody. His precaution turned out to be prescient. This was one of at least four occasions on which he would be forced to revert to a recording in order to dispute another version of the meeting.

The recording was handed in and O’Higgins had it verified. The superintendent was called to give evidence, which turned out not to coincide with the CSSO document.

Nothing more was heard of this matter until a year later days after the O’Higgins report was published. On May 15, 2016, the Irish Examiner broke the story of what had occurred behind the closed doors of the commission.

The Disclosures Tribunal will now examine in detail what transpired during those hearings at O’Higgins. In particular, it will examine how the commission could have been informed that there were two meetings in which McCabe had expressed anger or a grudge, which would have portrayed him as a man ill disposed towards An Garda Síochána for personal reasons.

This stuff is deadly serious. It may be attributable to misunderstandings, mix-ups, mistakes. If so, the carelessness shown to somebody who had been through what McCabe had endured, and a complete subsequent failure to even contact him to explain or apologise, was inexcusable.

The alternative explanation — that a person or persons were out to attack McCabe’s character on a false premise — is even more arresting. The tribunal will have some very serious deliberating to undertake.

Among the witnesses scheduled to appear in the first two weeks of the hearings are Nóirín O’Sullivan, the senior counsel who represented her at O’Higgins, Colm Smyth, and Anne Marie Ryan, a solicitor who worked in the Chief State Solicitor’s office.

Maurice McCabe is also scheduled to give evidence in relation to his module.

The tribunal will also examine the extent of the knowledge of what was happening at the commission around May 2015. The civilian head of human resources in An Garda Síochána, John Barrett, has told the tribunal that a colleague informed him in the weeks before the commission hearings began that, “we are going after Maurice at the commission”.

The other person who had some knowledge of what was occurring was then minister for justice, Frances Fitzgerald. She resigned over the issue in November and has claimed that she will be “vindicated” at the tribunal.

How far Judge Charleton intends to go in relation to Fitzgerald’s position, and whether he considers her possible vindication to be included in the terms of reference remains to be seen.

The final module of the Disclosures Tribunal, which will follow the O’Higgins module, concerns whether or not there was a smear campaign against McCabe conducted by senior Garda management.

This allegation originated with a protected disclosure made by the former head of the Garda press office, Superintendent David Taylor.

He has alleged that he briefed journalists on foot of instructions from then commissioner Martin Callinan that McCabe had questions to answer in relation to child sexual abuse.

Taylor says he was acting on instructions, and claims that Nóirín O’Sullivan, who was deputy commissioner at the time, was fully aware of the campaign.

Both Callinan and O’Sullivan deny vehemently any knowledge of a smear campaign.

A number of high-profile journalists will be called to give evidence in relation to briefings from Supt Taylor, and/or other senior gardaí.

Taylor has waived any right to privilege as a journalistic source.

Whether or not journalists are willing to give evidence about the briefings remains to be seen.

There will also be evidence from TD John McGuinness. He claims that he was briefed by Callinan about McCabe in a meeting in a car park outside Dublin in January 2014. This was a few days before McCabe was due to give evidence before the Dáil Public Accounts Committee, of which McGuinness was chairman.

The Kilkenny TD has provided the tribunal with a statement about the car park meeting. He claims Callinan asked him was he aware of issues surrounding McCabe.

The TD replied he had heard rumours about child sexual abuse but that he had been assured by McCabe that there was no truth to it.

“Mr Callinan stated to me that the rumours were true, that Mr McCabe had sexually abused someone and that he was not a credible person,” according to John McGuinness’ statement.

He went on: “Mr Callinan stated that an investigation into Mr McCabe’s activities was underway.

“Mr Callinan then asked me was I aware that Mr McCabe had abused family members.

“I was shocked and extremely troubled by what Mr Callinan was telling me because the allegations being made were extremely serious and the person relaying them to me was the commissioner of An Garda Síochána.”

Callinan denies ever saying any of these things. All such allegations about McCabe are completely untrue and scurrilous.

Judge Charleton will have to decide whose version of the meeting he accepts.

The comptroller and auditor general Seamus McCarthy, who keeps a very low public profile, has also provided a statement to the tribunal over what he alleges were comments made to him by Callinan. These comments differed only in emphasis from those that McGuinness claims were made to him.

There will also be evidence from RTÉ presenter Philip Boucher Hayes on foot of a statement he has made about what he alleges Callinan said to him about Sgt McCabe.

Judge Charleton has indicated that he hopes to finish public hearings before Easter, but these things have a habit of taking on a life of their own. The hearings are bound to be dramatic and may even be sensational.

However, far more important is the substance of the issue. Sgt McCabe and his family are entitled to know what, if any, lengths were gone to by agents of the State to attack him, shut him up, or even destroy his character.

On a broader front, the matter at issue goes to the heart of the operation of a democracy and the rights that citizens are supported to have therein.