The Disclosures Tribunal has found that Sgt Maurice McCabe was "repulsively denigrated for being no more than a good citizen and police officer".
The tribunal, which is chaired by Justice Peter Charleton, has published its third interim report.
The report follows its hearings investigating whether there was a smear campaign orchestrated by Garda management against the Garda whistleblower.
Justice Charleton says it "has been a dreadful struggle to attempt to uncover what may have gone on behind closed doors".
“Campaign of calumny”
The report is strongly critical of both the Former Garda Commissioner Martin Callinan and the former Garda Press Officer Dave Taylor – finding that both men were involved in carrying out a “campaign on calumny” against Sgt McCabe.
In particular, it finds that Commissioner Callinan told a Dáil TD in 2014 that Mr McCabe had sexually abused his own family and one other person.
The allegations concerning Sgt McCabe’s family were completely false.
The other allegation, made by a woman known as Ms D, was fully investigated, with the DPP concluding in 2007 that no offence had been committed.
Former Garda Commissioner Martin Callinan
Car park meeting
The report outlines the evidence given by John McGuinness TD, the former head of the Public Accounts Committee.
Deputy McGuinness told the tribunal that during a meeting in a car park in west Dublin in 2014, Commissioner Callinan told him that Sgt McCabe was not a credible witness to bring before the PAC because “he had sexually abused his family and an individual.”
He said the then-commissioner told him that “there was a file there and that action would be taken against Sergeant Maurice McCabe.”
“[Commissioner Callinan] gave me to believe that there was an investigation ongoing in relation to the allegations and that they were at an advanced stage and I immediately presumed from that that Sergeant Maurice McCabe would be charged with something or other,” Deputy McGuinness told the Tribunal.
He also said that at a previous meeting, Commissioner Callinan told him “this man fiddles with children.”
John McGuinness TD
Mr Callinan has rejected Deputy McGuinness’ account of the conversation and the report notes he had a "had a radically different view of the car park meeting."
However, Justice Charleton noted that based on the evidence he had heard: “The conversations as described by John McGuinness TD took place.”
Turning to Mr Callinan’s replacement as commissioner, Justice Charleton noted that Nóirín O’Sullivan denied any knowledge of the meeting until it was brought up in the Dáil two years later.
He said there is nothing in the evidence to show otherwise.
Regarding the former Garda Press Officer Dave Taylor, the report criticises what it calls his 'disgraceful behaviour' - describing him as a witness "whose credibility was completely undermined by his own bitterness".
It notes: "What has to be remembered here is that Superintendent David Taylor had an agenda.
"The evidence for his disgraceful behaviour in leaking police investigation details to selected ‘friends’ of his in the media was electronic."
Superintendent David Taylor arriving at the Disclosures Tribunal in Dublin Castle. Photo: Leah Farrell/RollingNews.ie
It adds: "He was in danger of being charged with a criminal offence. He was also facing disciplinary proceedings.
"To undermine all the dangers he had put himself into, his strategy was to garner public sympathy by creating a fuss specifically directed at what he deceitfully was claiming was the unreliability of evidence against him. He therefore claimed that his phones were manipulated by garda conspiracy."
It also accuses him of laying an "entirely deceitful affidavit" before the High Court.
It adds that Superintendent David Taylor completely understated his own involvement in a "campaign of calumny" against Maurice McCabe and that it was not the case that he acted under orders.
"The tribunal is convinced that he pursued a scheme that somehow evolved out of his cheek-by-jowl working relationship with [then Garda Commissioner Martin Callinan]," the report suggests.
It further claims that Callinan "personally felt the need to supplement the efforts of his press officer".
The report also strongly criticises the child and family agency Tusla for its handling of the false rape claim made against Sgt McCabe.
It says the false report had an "afterlife" within Tusla, observing: "This was not due to any action by gardaí, but was because of the astounding inefficiency of that organisation and the inertia of its management in Cavan/Monaghan."
'Cultural shift needed'
According to the report, mistakes or failure to correct mistakes "had nothing to do" with former Garda Commissioner Noirín O'Sullivan.
It also says RTÉ journalist Paul Reynolds was "in no sense... a tool of the higher echelons of Garda Headquarters."
The report calls for a 'complete turn-around' in Garda attitudes, saying they "offered no criticism of themselves".
It calls the police force a "resource of brilliant men and women" in need of leadership.
"A cultural shift requiring respect for the truth is needed," it adds.
The report praises Maurice McCabe as "a genuine person" who at all times had "the interests of the people of Ireland uppermost in his mind".
It adds: "Maurice McCabe has done the State considerable service by bringing these matters to the attention of the wider public and he has done so not out of a desire to inflate his public profile, but out of a legitimate drive to ensure that the national police force serves the people through hard work and diligence.
"He is an exemplar of that kind of attitude."
File photo of Garda Commissioner Drew Harris during a press conference at Garda Headquarters in Dublin, 04-09-2018. Image: Liam McBurney/PA Wire/PA Images
This afternoon, the new Garda Commissioner Drew Harris said the force “fully accepts the findings of Mr Justice Charleton.”
“Mr Justice Charleton’s Report makes for difficult reading for the organisation, but it is vital that we take it as an opportunity to change how we operate so we provide a professional and ethical service to the public," he said.
“I fully agree with Mr Justice Charleton when he states that the obligation for members of An Garda Síochána is to the truth, society and the vulnerable, and not to the organisation.”
Commissioner Harris said he was establishing a group to examine the findings from “policy, process, discipline and cultural perspectives to identify the lessons to be learnt and changes to be made.”
He said he welcomes and supports the findings in relations to Sergeant McCabe.
“I acknowledge the difficult time he and his family have endured and I hope this chapter is drawing to a close,” he said.
“I will ensure Sergeant McCabe and all Garda personnel referenced in the report receive appropriate supports.
"I will ensure An Garda Síochána is a safe environment for people to raise issues or concerns. The organisation will improve by having an open and inclusive culture.”
He said it would not be appropriate for him to comment “at this stage” on the findings relating to other individual gardaí.
This afternoon, the agency again offered a "sincere apology" to the McCabe family for the "impact Tusla’s errors had on them."
"Tusla is sincerely sorry that its standards did not meet those which could be reasonably expected by Sergeant McCabe and his family," it said.
"Additionally, Tusla also wishes to apologise to others who were affected by the errors that were made.
"Tusla will now study the findings in detail to enhance our current programme of reform and improvement, where possible."
It said it will issue a full response when it has had the opportunity to study the 400 page report in detail.
Additional reporting from Michael Staines ...