Sergeant Maurice McCabe was entitled to be vindicated as truthful by the Charleton Tribunal, his barrister has said in closing submissions.
"He doesn't come here as a plaster saint and he doesn't say that he got everything right," Michael McDowell SC told the tribunal.
"But he is entitled to be vindicated as a man who has been truthful, not only at the O'Higgins Commission but also in this tribunal, and that he is well motivated."
The O'Higgins Commission of Investigation looked at complaints by Sgt McCabe about policing on the Cavan-Monaghan division. The Charleton Tribunal had been looking at allegations that there was a smear campaign against Sgt McCabe.
Mr McDowell said there was no evidence that RTÉ journalist Philip Boucher-Hayes had any motive to make up his account of his conversation with Garda Commissioner Martin Callinan in December 2013, and other witnesses had confirmed that Mr Boucher-Hayes had told them about the conversation.
Comptroller and Auditor General Seamus McCarthy was a public servant and "had no basis whatsoever to impugn Mr Callinan", Mr McDowell said.
Mr McDowell said that Mr McCarthy's evidence of what he was told by Mr Callinan before a Public Accounts committee (PAC) meeting on 23 January, 2014, confirmed to some extent what John McGuinness TD said he was told in a car park meeting with Mr Callinan on the following day.
Mr McDowell said that Fine Gael TD John Deasy had been sympathetic to Mr Callinan's position on whether Sgt McCabe should give evidence before the PAC, and there was no reason to suppose Mr Deasy held any malice towards Mr Callinan.
Mr McDowell said that Shane Murphy, SC on behalf of the garda commissioner, was asking the tribunal to consider that Mr McGuinness invented "a highly malicious story" and was re-telling it knowing it to be false.
Mr McDowell said this would mean believing that a note of the meeting made afterwards by Mr McGuinness was "a piece of forged documentation invented to corroborate his account", and that the tribunal should also doubt the evidence of Fianna Fáil leader Micheál Martin, who said he was told about the meeting some weeks later.
Mr McDowell said it was likely that some journalists were negatively briefed about Sgt McCabe by former press officer Supt Taylor.
He said there was not "a simple binary choice" that Supt Taylor was either credible or not credible as a witness. Mr McDowell said it was unusual that Supt Taylor was reinstated and disciplinary proceedings dropped after the the findings of the Clerkin report, which found he was leaking information to journalists.
"The attitude exhibited in the witness box by Supt Taylor seems to have had about it an acquiescence and an willingness not to fight his corner and to rely on entirely formulaic statements of evidence in circumstances which must attract a degree of suspicion," Mr McDowell said.
Rossa Fanning SC, on behalf of Independent News & Media (INM), said there was no evidence that INM was used even inadvertently as part of a smear campaign against Sgt McCabe.
Any fair examination would show INM reported fairly on Sgt McCabe's allegations, and that often its coverage was favourable to him, Mr Fanning said.
Journalistic gossip was not relevant to the tribunal, and journalistic clashes as to the currency of gossip were of no probative value to the tribunal, Mr Fanning said.
Counsel said there were three disputes which concerned INM, involving journalists Ann Harris and Gemma O'Doherty, and academic Colum Kenny.
"The tribunal should exercise caution and restraint in not deciding things, it is not for the tribunal to decide," Mr Fanning said.
Mr Fanning said that if the tribunal did take a view on the differences between evidence, then in respect of Ms Harris, it should prefer the evidence of Fionnán Sheahan and Ian Mallon.
He said there was no objective evidence that the termination of Gemma O'Doherty's employment had anything to do with garda interference.
Mr Fanning said that journalist Tom Brady was "emphatic" that he did not have a discussion with Colum Kenny, in the presence of RTE journalist Paul Reynolds or otherwise, and never had a discussion of the kind outlined to the tribunal by Mr Kenny.
In closing remarks, the chairman Mr Justice Peter Charleton thanked all those who had worked to make the tribunal a success since it began, and the members of the public who had attended its sittings.
"I couldn't have done any better, because I have worked with the best," the chairman said.
The chairman said he expected to complete his report in October.