The Department of Justice insist the former Tánaiste Frances Fitzgerald could not do anything about the Garda legal strategy to discredit Maurice McCabe.
Acting Secretary General of the Department Oonagh McPhillips said that Ms Fitzgerald could have convened her senior officials to query the strategy at the O'Higgins Commission.
However, speaking at an Oireachtas Committee, Ms McPhillips insists the then-Minister could not have tried to stop the former Garda Commissioner's approach.
"If the Minister was to express that view to the Commissioner in relation to a matter before a Commission of Investigation, that could be deemed, subsequently, to have been interfering in the Commissioner's rights before the Commission," she said.
"And obviously if the issue of disciplinary proceedings, or any kind of proceedings, arose subsequent to the findings of the Commission, the Minister would have compromised herself."
The Justice Department will answer questions on the Maurice McCabe scandal today.
A string of departmental emails discussing the legal strategy against the Garda whistleblower emerged, which led to the resignation of the Tánaiste, is set to be the main topic of discussion.
The acting Secretary General will acknowledge that mistakes have been made but will also defend the work of the Justice Department.
Oonagh McPhillips will maintain that they handed over all documents to the Disclosures Tribunal, despite the fact that the emails about the strategy against Sergeant McCabe were not included.
Deputy Fitzgerald insists she did nothing wrong, and Ms. McPhillips will confirm that they would always advise a Minister not to get involved in any case before a Commission of Investigation.