"One of the challenges in this case, it seems to me, is that the two principal witnesses have real credit issues," Justice Michael Lee said on Thursday.

The judge said, in his consideration of the high-profile case, he could not accept "various parts" of Ms Higgins' and Mr Lehrmann's evidence.

"We agree," Matthew Collins KC, representing Network Ten, responded.

The Federal Court is hearing closing submissions following weeks of evidence in the defamation proceedings brought forward by Mr Lehrmann against Lisa Wilkinson and Ten.

Mr Lehrmann is suing the parties over a story The Project aired in 2021 which he claims ruined his reputation by identifying him as the man accused of raping Brittany Higgins in a ministerial office two years earlier.

Mr Lehrmann and Ms Higgins have both been subjected to multiple days of intense cross-examination, during which fine details of their distinctly opposite accounts were expertly analysed and criticised.

At times, they were each proven to have previously given false evidence and even lied.

In summarising key defence points on Thursday morning, Dr Collins described Mr Lehrmann as a "fundamentally dishonest man who was prepared to say or do anything he perceived to advance his interest".

"[Mr Lehrmann] was wholly unconcerned with giving the court an honest account of the events of the 22nd and 23rd of March, 2019," he said.

"Remarkably, he is an applicant who seeks the aid of the court to vindicate his reputation in respect to a report and an event in circumstances where he's given [knowingly false] evidence in respect of almost every significant integer concerning that event."

The barrister conceded that "successful attacks" were made on the credit of both Mr Lehrmann and Ms Higgins during the trial's cross-examinations.

"But we would submit that the success of those attacks was qualitatively different," he told Justice Lee.

Dr Collins said the judge should approach the entirety of Mr Lehrmann's evidence "with extreme suspicion" after he had been a "combative and defensive" witness.

In contrast, he said Ms Higgins evidence was "compelling and distressing, and in our submission, it was believable".

The court heard a number of corroborated "facts", denied by Mr Lehrmann, which Dr Collins argued specifically went against the former Liberal staffer turned law student's credit.

They included details like Mr Lehrmann finding Ms Higgins attractive, which former staffer Nicola Hamer told the court he had expressed to her.

Dr Collins said Mr Lehrmann repeatedly denying purchasing drinks for Ms Higgins hours prior to the alleged rape, as caught on CCTV, as a "bizarre piece of dishonesty".

The court heard denied "facts" like encouraging her to drink, that they had spent a substantial amount of time together that night, helping her up from a fall, and the pair "pashing" in a nightclub, all went against his credit.

Ms Higgins made several concessions throughout her evidence, including she could no longer be certain a crucial leg bruise had been caused by Mr Lehrmann or if she was certain of wearing a dress during the alleged assault.

On Thursday afternoon, Sue Chrysanthou SC, representing Ms Wilkinson, presented closing submissions on behalf of her client.

She ran through more of Mr Lehrmann's claims she described as "bizarre lies".

They included: making question time notes during his after-hours Parliament House visit; that he earlier had vital conversations about the French submarine contract; purposefully leaving his keys in the ministerial office; having two phones with him; and accidentally missing multiple phone calls from his girlfriend throughout the night.

Ms Chrysanthou told the court there was no doubt sex had occurred in the early hours of March 23, 2019, and that the debated issue should only be one of consent.

But instead, the court heard, Ms Higgins had been portrayed as a "fantasist" for having allegedly fabricated the incident.

"She's being accused of plainly making up the whole thing," the barrister said.

Ms Chrysanthou said text messages from Ms Higgins to friend Ben Dillaway in the following days showed she had debated her own role in, and possibly misleading Mr Lehrmann ahead of, the alleged rape.

But in those messages, the court heard, was "no hesitation" a sexual act had occurred.

A recorded phone call between Ms Higgins and journalist Samantha Maiden detailed the former Liberal staffer's apparent shock at Mr Lehrmann's denial of any sexual act occurring on the night in question.

"If they didn't have sex, why was she naked?" Ms Chrysanthou asked, referring to Ms Higgins being found naked in Senator Linda Reynold's office.

"It doesn't make a lot of sense. Unless there was some sort of freak heatwave that night in Canberra ... it seems unusual she had no clothes on."

The highly publicised trial has heard emotional, combative and revelatory testimonies from a range of key witnesses in the case surrounding the sexual assault that allegedly took place almost five years ago.

Ms Wilkinson and The Project producer Angus Llewellyn each previously sat in the witness box to vehemently defend their professionalism in putting together the broadcast.

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For weeks, the high profile journalist and Ten have worked to prove the rape allegation is substantially true, and reporting it accurately and reasonably was in the public interest.

Earlier on Thursday, Dr Collins told Justice Lee that even if the defences failed, the judge may be facing a case where "your honour ought not to award any damages".

Mr Lehrmann has already settled defamation suits with the ABC and News Life Media, totalling $445,000. He sued the media companies over the reporting and broadcast of Ms Higgins' allegation.

He has always denied raping Ms Higgins at Parliament House in 2019, when the pair worked as staffers for the then-defence industry minister.

No findings have been made against him.

Mr Lehrmann's criminal trial was aborted last October because of juror misconduct, with the charge of sexual intercourse without consent levelled at him later discontinued over concerns for Ms Higgins' mental health.

The defamation trial continues and is expected to finish on Friday.