Walter Sofronoff KC has asked the Federal Court to throw out a March finding by the ACT Integrity Commission that the former judge engaged in serious corrupt conduct.
The commission's probe stemmed from Mr Sofronoff's leaks of confidential witness statements and the probe's final report to a journalist.
But the watchdog's adverse finding was a "serious offence against the administration of justice", Mr Sofronoff's barrister Adam Pomerenke KC said during a hearing on Monday.
Mr Sofronoff was not corrupt, malicious or dishonest, the barrister told Justice Wendy Abraham.
Rather, he genuinely believed he was acting in the public interest by sending documents such as witness statements to the media.
"Even if Mr Sofronoff was wrong in his view, the fact remains that he genuinely and honestly held it," Mr Pomerenke said.Â
"At worst it could be characterised as an erroneous attempt to ensure accuracy and transparency in the public discourse."
The ACT Integrity Commission backed its findings.
Its barrister Scott Robertson SC said Mr Sofronoff had "threatened public confidence" in the integrity of the government and public administration through his conduct.
The ex-judge had breached his non-disclosure obligations by leaking the material, Justice Abraham was told.
Mr Sofronoff chaired a board of inquiry into the ACT's criminal justice system after Lehrmann's controversy-plagued prosecution.
Former Liberal staffer Lehrmann was accused of raping then-colleague Brittany Higgins at Parliament House in 2019.
A criminal trial in 2022 was abandoned without a verdict because of juror misconduct.
Lehrmann lost a defamation lawsuit he brought over media reporting of Ms Higgins' allegations but has appealed a judge's finding the rape claim was true on the balance of probabilities.
The Sofronoff-led inquiry found the ACT's top prosecutor, Shane Drumgold, had lost objectivity over the Lehrmann case and knowingly lied about a note of his meeting with broadcaster Lisa Wilkinson.
Mr Drumgold resigned and launched a legal challenge to the findings in the ACT Supreme Court.
It found the majority of the inquiry's findings were not legally unreasonable, but it struck down an adverse finding about how Mr Drumgold cross-examined then-Liberal senator Linda Reynolds during Lehrmann's trial.
The ACT Integrity Commission in March also found the majority of the 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 columnist and provided her an advance copy of his probe's final report.
Mr Pomerenke told the Federal Court on Monday the ACT corruption body had admitted it made an error finding Mr Sofronoff might have engaged in contempt.
The claimed contempt stemmed from leaks to the media despite directions made to parties during the inquiry to suppress certain documents.
But the notion the head of an inquiry could be in contempt of himself was "absurd and irrational", Mr Pomerenke said.
This concession was enough to toss the findings against his client, he told the court.
Any individual error could not be "disentangled" from the final finding Mr Sofronoff engaged in serious corrupt conduct, the barrister said.
Mr Robertson disagreed, saying the "ultimate finding" of serious corrupt conduct still stood despite the admission.
Even before reaching the conclusion Mr Sofronoff had engaged in corruption, the commission found he lacked probity and undermined public confidence, he said.
The conduct was such that if Mr Drumgold learned of if before the report was handed down, he could have applied for the ex-judge to be removed as chair of the corruption inquiry, Mr Robertson argued.
The hearing continues.
