Mr Callinan also said he absolutely refutes 'crazy and very serious allegations' against him
Martin Callinan has admitted at the Disclosures Tribunal that appointing Dave Taylor as garda press officer was one of the worst mistakes of his life.
The former garda commissioner has finished after three days of evidence at the tribunal.
The tribunal is currently examining whether garda management directed Superintendent Dave Taylor to brief journalists negatively about Maurice McCabe.
Mr Callinan has denied directing Superintendent Taylor to smear the garda whistleblower - and there is no evidence of such a campaign, other than the testimony of the former garda press officer.
After three days of evidence from the former commissioner, the Tribunal Chairman said 'I still can't understand why you chose Dave Taylor - it must be one of the worst mistakes of your life'.
Mr Callinan said 'I absolutely agree.'
Peter Charleton asked was Superintendent Taylor that devious that he sought to curry favour by being hostile to Maurice McCabe - to which Mr Callinan said 'It's certainly a side of Superintendent Taylor that I knew nothing about.'
Earlier, Mr Callinan denied suggesting that Fianna Fail TD John McGuinness has invented evidence against the former garda commissioner.
Mr Callinan said he absolutely refuted the ‘crazy and very serious allegations’ made by Deputy McGuinness when he said the Commissioner told him Sergeant McCabe had abused his own children.
Mr Callinan said Deputy McGuinness had a duty as a public representative to report the allegations earlier.
The former commissioner found himself in the uncomfortable position that his recollection of conversations with five men is different from their own.
It was put to Mr Callinan that he was inviting the tribunal to reject as complete malicious invention the statement of John McGuinness that the former Commissioner told him that Maurice McCabe had abused his own children.
Mr Callinan said he absolutely refuted the 'crazy and very serious allegations' against him, and he said that Deputy McGuinness had met with two witnesses to the tribunal before making his statement - adding that he himself hadn’t met with any other witnesses.
Counsel for Maurice McCabe said: "Are you seriously suggesting that somehow Sergeant McCabe put John McGuinness up to telling lies about you?"
Mr Callinan said he was not, but he found it disconcerting that the two men met prior to the tribunal.
He also said that Mr McGuinness had a duty as a public representative to bring the allegations to the attention of government.