Walter Sofronoff KC has asked the Federal Court to toss out the ACT corruption watchdog's findings delivered in March, stemming from leaks to a journalist.
Justice Wendy Abraham on Tuesday heard arguments from Alison Hammond, for the ACT parliament's speaker, that the Integrity Commission's report into Mr Sofronoff's Lehrmann inquiry is protected by parliamentary privilege.
Mr Sofronoff chaired a board of inquiry into the ACT's criminal justice system after controversy plagued the prosecution of Lehrmann, accused of raping then-colleague Brittany Higgins in a ministerial office at Parliament House in 2019.
A 2022 criminal trial was abandoned with no verdict because of juror misconduct.
On Tuesday Ms Hammond said the ACT speaker submitted that the corruption report was a proceeding in parliament "such that parliamentary privilege attaches to it".
Mr Sofronoff's claim would infringe that privilege and should be dismissed, she said.
"There is a sufficiently close functional connection between a report prepared by the commission ... and the work of the legislative assembly so as to attract parliamentary privileged content."
The speaker's position was that a challenge to or judicial review of a corruption inquiry was available to applicants but not after a report was completed and submitted to the speaker, Ms Hammond said.
Adam Pomerenke KC, for Mr Sofronoff, argued the corruption investigation had occurred outside empowering statutes, while errors in the report had already been admitted.
"It's this publication on the commission's website, outside the legislative assembly, publication to the world, which is doing the real damage on our case to Mr Sofronoff's reputation."
The Integrity Commission's duty to expose corruption "has nothing to do with the legislative assembly", Mr Pomerenke said.
"The mere tabling of a document in parliament ... is not part of enacting the business of the house or committee."
The Sofronoff inquiry found the ACT's top prosecutor, Shane Drumgold, had lost objectivity over the Lehrmann case and had knowingly lied about a note of his meeting with broadcaster Lisa Wilkinson.
The ACT Integrity Commission found the majority of the Sofronoff inquiry's findings were not legally unreasonable.
But it found Mr Sofronoff's behaviour during the inquiry gave rise to a reasonable apprehension of bias and he might have been influenced by the publicly expressed views of journalist Janet Albrechtsen.
Mr Sofronoff repeatedly messaged the News Corp journalist and eventually leaked her an advance copy of his probe's final report.
That leak led to the Integrity Commission's "serious corrupt conduct finding" in March.
Justice Abraham reserved her decision on the bid to dismiss Mr Sofranoff's court challenge.
