The war veteran's barristers began closing his Federal Court case on Monday, more than 100 days after commencing the proceedings against journalists and three mastheads.
The Victoria Cross recipient is seeking aggravated damages of up to 10 years or more in lost income from jobs including a partnership with consulting firm PwC and lucrative public speaking.
But Nicholas Owens SC representing the mastheads being sued for defamation said Justice Anthony Besanko faced irreconcilable accounts from Mr Roberts-Smith's friends harbouring a motive.
"Your Honour is confronted with a dilemma that someone is lying," Mr Owens said.
Mr Roberts-Smith is suing for defamation The Age, The Sydney Morning Herald and The Canberra Times over 2018 reports claiming he committed war crimes in Afghanistan including murder, and acts of bullying and domestic violence.
The 43-year-old denies all claims of wrongdoing, while the mastheads are defending them as true.
The oft-described trial of the century, and a proxy war crimes trial attacking freedom of press, is actually about Australia's most decorated soldier having a high reputation for courage, skill and decency that has now been destroyed, Arthur Moses SC said.
"It is about the respondents using the processes of this court to make allegations of murder which will have both national and international repercussions for the applicant and other members of the Australian Defence Force who they have accused of murder," he said.
Mr Roberts-Smith's bravery was awarded with the prestigious and rare Victoria Cross, and consequently created an unexpected "target on his back".
Mr Moses said journalists Chris Masters and Nick McKenzie based sensationalist publications on rumour, hearsay and contradictory accounts from jealous and obsessed former colleagues, including politician and former SAS officer Andrew Hastie.
Matthew Richardson SC, also acting for Mr Roberts-Smith, said he was formerly known as a hero.
"But is now thanks to the respondents, a man wildly reviled as a murderer and an abuser of women," Mr Richardson said.
He pointed to Mr Roberts-Smith's evidence that he was traumatised watching his family's good named dragged through the mud, and that it had crushed his soul.
"I gave so much to that job and it's all lies," Mr Roberts-Smith said in evidence.
He is fighting allegations of six murders he either committed or was said to be complicit in Afghanistan between 2006 and 2012.
Mr Moses cited one allegation of shooting a 13 or 14-year-old boy as unjustified.
"The allegation is baseless and should not have been persisted with. Presumably it was persisted with in order to damage Mr Roberts-Smith in aid of the other allegations which have been propounded in this matter," Mr Moses said.
Mr Owens argued that his witnesses were not accused of deliberate dishonesty, but had "remembered incorrectly" due to the passage of time coupled with exposure to rumours.
He said there was a stark difference between someone forgetting what they had for breakfast 13 years ago, and the execution of a prisoner.
Several of these witnesses were "getting on with their lives," and had made no attempt to come and give allegedly damning evidence against their former comrade, but had been legally forced to do so.
This contrasted with all Mr Roberts-Smith's chosen eyewitnesses to a key allegation two prisoners were murdered at the Taliban compound dubbed Whiskey 108.
"It is no coincidence they are very close friends ... in some cases godparents and business associates ... a very close unit of people communicating regularly with obvious affection for one another."
The closing submissions from both parties are expected to last eight days.
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