The controversy around garda whistleblower claims has already forced the resignations of former justice minister Alan Shatter and ex-garda chief Martin Callinan. 

And now Garda Commissioner Nóirín O'Sullivan is facing calls to step down over reports that her legal team sought to undermine complaints brought by Maurice McCabe.

Not sure what's going on? 

Let’s start at the beginning. Who’s Maurice McCabe ?

Maurice McCabe is the garda whistleblower whose allegations formed the basis of the O’Higgins investigation.

Mr McCabe was serving as a sergeant at Bailieboro, Co Cavan, when he became concerned about the force’s handling of suspected criminal offences in late 2007.

In 2008, he submitted a file to garda authorities alleging malpractice and corruption in his own division of Cavan-Monaghan.

He later brought a series of complaints to the confidential recipient, the official charged with processing garda grievances about the force.

The bulk of his allegations related to alleged failures in a number of garda investigations and the handling of penalty points.

A dossier detailing these claims was then taken up by Fianna Fáil leader Micheál Martin, who passed them on to Taoiseach Enda Kenny in February 2014.

How does the Guerin report come into this?

Senior counsel Seán Guerin was appointed by the government to conduct an independent review of Mr McCabe’s allegations in February 2014.

In his report, published three months later, Mr Guerin recommended that a comprehensive commission of investigation be established to look into the claims.

The Guerin report strongly criticised the then justice minister Alan Shatter for the way he dealt with the whistleblower.

That controversy led to Mr Shatter’s resignation in May 2014 - a move he subsequently claimed was forced on him by Taoiseach Enda Kenny.

Photo: Alan Shatter | RollingNews.ie

What did the O’Higgins commission have to say about the allegations?

The commission, established on the foot of the Guerin findings, reported last week that Mr McCabe had “performed a genuine public service at considerable personal cost” and “acted out of genuine and legitimate concerns”.

The commission’s final report highlighted serious flaws in policing in the Cavan-Monaghan division and said a number of victims were “not well-served” by local gardaí.

However, it found no evidence to support claims of garda corruption in the district.

While some of Mr McCabe’s complaints were upheld, others were deemed to be either unfounded or overstated.

The O’Higgins report also found Mr Shatter had taken whistleblower concerns “very seriously” - a conclusion the ex-minister has said clears him of any wrongdoing.

Why is Nóirín O’Sullivan now being criticised?

The garda chief has come under mounting pressure to respond to claims her legal team accused whistleblower Maurice McCabe of “malice” in unpublished documents from the inquiry.

The Irish Examiner reported last week that a barrister for Ms O’Sullivan had been instructed to question Mr McCabe’s motivation in bringing complaints against the force.

The inquiry was told that two officers had taken notes at a 2008 meeting in which it was alleged the sergeant said his accusations arose from a grudge he held against a senior officer. 

However, Mr McCabe reportedly presented the O’Higgins commission with a tape of the meeting that disproved the claim and no mention of the exchange is made in its final report.

Photo: Maurice McCabe | RollingNews.ie

According to documents seen by RTÉ News, senior counsel for Ms O’Sullivan later told the inquiry it was an “error on his part” to have earlier suggested she had ordered him to question the whistleblower’s integrity.

In a statement earlier this week, Ms O'Sullivan claimed she was legally prevented from commenting on private evidence given to the commission.

She stressed that she never regarded Mr McCabe as malicious and that the service had “changed for the better in response to the issues about which he complained”.

But the garda chief, who was appointed to the position following the resignation of Martin Callinan, is now facing calls to step down.

Speaking in the Dáil last night, TD Clare Daly told Tánaiste Frances Fitzgerald that it was time for Ms O’Sullivan “to go”.

TD Mick Wallace also called on her to step aside, saying she was “not fit to be the commissioner”.

“You’re not going to change how we do policing in Ireland until we change the hierarchy,” he said.

How has the government responded?

Minister for Justice Frances Fitzgerald insisted last night that she had “every confidence” in Nóirín O’Sullivan’s commitment to taking forward  policing  recommendations made in the report.

The Fine Gael TD said she too was legally constrained from commenting on private evidence given to a commission.

She also cast doubt on the legal advice received by Labour that said lawyers were excluded from the ban on publishing such evidence.

“It seems to me it would be a significant change to the generally accepted position that communications between a lawyer and client should not have to be put in the public domain,” she said.   

But the minister appeared to row back on this position today, saying in the Dáil this morning that she had “no doubt” the commissioner would clarify the points that have been raised “as much as possible”.