An allegation of collusion among witnesses has surfaced in court during an ongoing defamation trial brought by war veteran Ben Roberts-Smith.

The resulting evidence could land a “knockout blow” against the media outlets which are fighting the Victoria Cross recipient’s legal action, the Federal Court was told on Friday.

The application was brought by Nicholas Owens SC on behalf of newspapers The Age, The Sydney Morning Herald and The Canberra Times.

The 43-year-old is suing the mastheads over reports claiming he committed war crimes in Afghanistan including murder, and acts of bullying and domestic violence.

Mr Roberts-Smith denies all allegations the news outlets are defending as true.

A “key battleground” in the case involves a soldier from Afghan’s partner force dubbed Person 12, who is placed on a mission in Khaz Oruzgan in October 2012, Mr Owens said.

The former SAS corporal is accused of ordering Person 12 through an interpreter dubbed Person 13 to shoot an Afghan prisoner during that mission.

But Mr Roberts-Smith allegedly colluded with four witnesses who are due to say Person 12 was stood down from the patrol in July and therefore could not have been present during the alleged murder.

Friday’s application suggests expected upcoming evidence from some of the witnesses showed Person 12 was removed after shooting a dog, and the bullet ricocheted and hit an Australian soldier.

“(This is a) knockout blow in relation to our case,” Mr Owens said.

Some of these statements include precise and large-scale falsehoods to create a fake alibi for Person 12, he said.

“We say that there is no explanation for that consistent with as it were coincidence or innocent mistake.

“We say to the relevant standard it shows a prima facie case of impropriety.

“The fraud is the collusion with the witnesses.”

Mr Owens is applying to have documents handed over by Mr Roberts-Smith’s legal team that have been earlier denied due to privilege.

Mr Roberts-Smith’s barrister Arthur Moses SC fired back that the interlocutory application was put forward in complete ignorance.

He said the “baseless” and serious allegations were not founded in evidence and were an attempt to prejudice the public and the court.

“The application should never have been brought and they should have known better.”

Mr Moses said it was not clear who Person 12 actually was, and multiple witnesses could fairly mistake his identity.

“It doesn’t mean they are perjurers or liars.”

“Who is Person 12? Who do they say that person is? And which of the myriad of images are to be accepted as person 12? Identification is key.”

It was was “gobsmackingly hypocritical” the defence had changed their pleading after mistaking Person 12 on another mission, he said.

“Then conspiracy theory runs large and they start throwing allegations around like confetti,” Mr Moses said.

“Behind every tree is a dark shadow according to the respondents.”

Justice Wendy Abraham has reserved her judgment on the application for a later date.

– AAP