The Garda Commissioner says her legal team was not told to question the integrity, or alleged malice, on the part of whistleblower Maurice McCabe.
The statement from Ms O'Sullivan is her first comment since the leak of partial transcripts from legal arguments at the Commission.
In those transcripts, her senior counsel said he had been told to raise allegations about Maurice McCabe's motivations and integrity, although the latter claim was withdrawn.
In her statement, however, Noirin O'Sullivan has defended the decision to cross-examine Maurice McCabe's testimony, and that of any witness.
She has also asked for two members of the force to be referred to the Garda Ombudsman, over a disproven claim that Sergeant McCabe had told them he was acting out of malice.
