Roberts-Smith denies hitting 'drunk' woman

Ben Roberts-Smith has denied domestic violence claims at his high-profile defamation lawsuit rejecting "deplorable" accusations that he struck a woman in Canberra in 2018.

Mr Roberts-Smith, 42, on Tuesday resumed his third day of testimony at the landmark Federal Court action launched against the publishers of the Sydney Morning Herald, The Age and The Canberra Times over articles from 2018 that he claims defamed him.

The war hero is suing the media outlets over claims of war crimes and murder during his Afghanistan deployments and accusations that he assaulted a woman, who cannot be named for legal reasons, at a Canberra hotel room in 2018.

After testifying behind closed doors for much of the day, Mr Roberts told the open court that he "absolutely" did not hit the woman, codenamed Person 17.

The court heard that on March 28, 2018 Mr Roberts-Smith and Person 17 drank a bottle of wine each at a Canberra vineyard before attending an event at Parliament House where he was assistant master of ceremony.

After the event Mr Roberts was waiting outside Parliament House for a COMCAR when a bystander told him that Person 17 had fallen down stairs inside.

The court heard Mr Roberts-Smith went back inside Parliament House to find her in the care of two Australian Federal Police officers who were holding her up.

"She had a significant bump over the top of her left eye," Mr Roberts-Smith said.

"She looked extremely intoxicated."

The court heard Mr Roberts-Smith and Person 17 then travelled back by COMCAR to Canberra's Hotel Realm where Person 17 "completely passed out" inside a room.

It was told Mr Roberts-Smith helped Person 17 into bed, checked her pulse, and placed an ice pack on her head where she had been injured from the fall.

"Did you at any time ... strike Person 17?" his barrister Bruce McClintock SC asked.

"No, I didn't," Mr Roberts-Smith replied.

Asked what he thought of domestic violence, Mr Roberts-Smith said: "I think it's deplorable, highly reprehensible ... I respect women a great deal".

"I find it a disgusting act of cowardice," he told the court.

He said claims by the respondents that he punched Person 17 had been "very difficult" and meant at times he found it hard even to leave the house.

"That particular allegation I feel, coupled with being called a war criminal, has ruined my life," Mr Roberts-Smith told the court.

"I have such disdain for those type of people."

Earlier, the court heard that he met Person 17 in October 2017 and started a relationship with her that he informed his wife about on a trip to Singapore in January 2018.

It was told that Person 17 subsequently told Mr Roberts-Smith that she was pregnant and that the former soldier hired a private investigator to take video of her over fears that he was being "manipulated".

"I just wanted to know the truth," he told the court.

On the war crimes claims, the court was told that Mr Roberts-Smith suspected the source of allegations against him by journalists was several former SAS associates and that he asked a private investigator to get the home addresses of a number of ex-colleagues in a bid to help his defence.

Mr Roberts-Smith denied giving the private investigator a threatening letter or threatening a witness known as Person 18, the court heard.

The ex-SAS corporal has previously testified that he never killed prisoners during his deployments to Afghanistan and has also rejected claims of bullying other SAS soldiers.

Mr Roberts-Smith's lawyers have argued that their client was subject to a lying campaign by failed soldiers and "bitter people" envious of the soldier's glittering military career and Victoria Cross.

The trial has heard that he was "devastated" by the outlets' claims and lost hundreds of thousands of dollars in income after his reputation was damaged by them.

He denies all the claims against him, while the publishers are relying on a truth defence.

The trial continues before Justice Anthony Besanko.