War veteran Ben Roberts-Smith's credit as a witness in his defamation case has been seriously — if not irretrievably — damaged because he has "shown himself prepared to lie under oath", a judge has been told.
The submission was made by Nine Entertainment's barrister Nicholas Owens SC, on a third day of closing addresses in the Federal Court in Sydney.
Mr Roberts-Smith is suing Nine over several 2018 newspaper articles in The Age, The Sydney Morning Herald and The Canberra Times, which he claims falsely painted him as a war criminal, a bully and a perpetrator of domestic violence.
Nine claims one alleged unlawful killing occurred during an October 2012 mission in Khaz Oruzgan, where Mr Roberts-Smith is accused of ordering, via an interpreter, a member of the Afghan Partner Force to shoot a local man being questioned.
The allegation, which Mr Roberts-Smith denies, created a dispute about whether the Afghan soldier, codenamed Person 12, was present because outlines of proposed evidence from the veteran and four of his SAS witnesses suggested otherwise.
The documents contained varying versions of the suggested reason why; that Person 12 was removed from the team months earlier, after he shot a dog and a ricocheting bullet injured an Australian soldier.
The four witnesses who raised the suggestion were Person 27, Person 32, Person 35 and Person 39.
Person 27 conceded in court his outline of evidence contained an error, while Person 32 said he had always been "under the assumption" the dog shooter was Person 12, and maintained that.
Person 35 admitted during his evidence that he had "remembered incorrectly" after being showed documents in closed court.
Person 39 told the judge he was informed during a briefing that Person 12 was the culprit.
Mr Roberts-Smith's legal team denied collusion.
Mr Owens on Wednesday made submissions about possible inferences to be drawn from the "lie", including impacts upon the credit of the witnesses.
He said the impact on Person 35 and Person 32's credit was "devastating".
"One then starts to build, well what is the probability of multiple people having the same assertedly innocent but wholly implausible false recollection?" he said.
"We say that the sheer improbability of one person having it is one thing, but once multiple witnesses start to have the same demonstrably false recollection, that leads squarely, as the most probable inference, to both deliberate dishonesty and collusion between them."
The barrister said Mr Roberts-Smith's credit was "seriously damaged, if not irretrievably", because his "false" evidence can only be seen as an attempt to corroborate two of his ex-colleagues.
"Mr Roberts-Smith has shown himself prepared to lie, under oath, on matters squarely relevant to the substantive issues in these proceedings," Mr Owens said.
Mr Owens said Mr Roberts-Smith was "either the architect or the knowing beneficiary of the collusion" and outlined why Justice Anthony Besanko could use the issue as a basis from which to infer a "consciousness of guilt".
Mr Roberts-Smith denies all wrongdoing and earlier this week, his barrister told the judge he was the victim of a "sustained campaign" from Nine to unfairly create the belief he committed war crimes.
Arthur Moses SC said the stories were based on rumour, hearsay and contradictory accounts from former colleagues, some of whom were "jealous" or "obsessed" with the veteran.
Closing submissions are expected to continue for another week.
