The Charleton Tribunal should disregard the evidence of four witnesses, including two TDs, in favour of the testimony of former commissioner Martin Callinan, a barrister for An Garda Síochána has said.
Shane Murphy SC said that the evidence of the four men - journalist Philip Boucher-Hayes, TDs, John McGuinness and John Deasy and comptroller and auditor general Seamus McCarthy - could not be regarded as corroborating each other, as they were each alleging different things were said during conversations with Mr Callinan about whistleblower Sgt Maurice McCabe.
The tribunal, which is examining allegations from former garda press officer Supt David Taylor that he was directed to brief negatively against Sgt McCabe, is hearing closing submissions before the chairman, Mr Justice Peter Charleton retires to write his report.
Mr Murphy said that a common element was that none of the witnesses had come forward at the time to report what they alleged Mr Callinan had said to them.
Mr Murphy said the evidence of Public Accounts Committee (PAC) chairman John McGuinness TD was inconsistent, as he told RTÉ interviewer Richard Crowley in 2016 that he had not made any notes following a January 2014 meeting in a Dublin hotel car park with Mr Callinan.
However in March 2017, Mr McGuinness produced notes of the meeting to the tribunal.
Mr Murphy said that Mr McGuinness also claimed on RTÉ that he had not spoken with Fianna Fáil party leader Micheál Martin about the meeting. Mr Martin told the tribunal last December that he was informed of the meeting.
The meeting had been characterised as somehow secret or clandestine, Mr Murphy said, but this was not the case.
The location, in a Dublin hotel car park, was chosen as Mr McGuinness was eager to get home to his Kilkenny constituency, and it was easier for Mr Callinan to travel to a meeting at Newlands Cross on the way out of city than in the city centre.
Mr Murphy said it was also Mr Callinan's position that comptroller and auditor general Seamus McCarthy was incorrect in his recollection of a conversation before a PAC meeting in January 2014, and that Fine Gael TD John Deasy had "misconstrued what was said".
Mr Callinan's case was that he was asked about allegations regarding Sgt McCabe by Mr McCarthy, and had told him that the allegations were investigated and the DPP directed no prosecution.
Mr Callinan also said he had told Mr Deasy that not all of the allegations made by Sgt McCabe had been proven, not that Sgt McCabe could not be trusted.
Mr Murphy said that RTÉ journalist Philip Boucher-Hayes' account of a conversation with the then commissioner in December 2013 contained a number of inconsistencies, and it was unlikely that the journalist would have prevented a broadcast going ahead because of a disagreement over what questions Mr Callinan should answer on air.
The chairman should also consider the impact of public commentary on memory, Mr Murphy said, as by the time the witnesses came forward in 2017 there had been "a vast tsunami of public discourse" about Sgt McCabe.
Mr Murphy also said that former garda press officer Supt David Taylor was not a witness who was in any way credible or whose evidence could be relied upon.
There was also no evidence of any communication between former commissioner Ms Nóirín O'Sullivan and journalist Debbie McCann in relation to Sgt McCabe, Mr Murphy said.
Mr Murphy also said there was no evidence produced to show Ms O'Sullivan had in any way influenced broadcasts by RTE journalist Paul Reynolds about a leaked copy of the report of the O'Higgins Commission of Investigation.