A UWA academic is under fire for lying to Tiwi Islanders who brought an eventually unsuccessful First Nations cultural heritage claim against Santos.

On Monday, federal court Justice Natalie Charlesworth dismissed claims by a small group of Traditional Owners in relation to the $5.8 billion gas project by Santos off the Northern Territory coast.

The Traditional Owners, who were represented by the Environmental Defenders Office (EDO), told the court there were several cultural features along the area of the pipeline route.

The plaintiffs - led by Jikilaruwu traditional owner Simon Munkara - wanted the federal court to order Santos to pause construction of its 263 km pipeline until the company had revised its environment management plan to include the potential risks: underwater cultural heritage sites and sacred dreaming places along the pipeline's route.

The West Australian reported the EDO said reports were commissioned confirming the pipeline would damage "sea country, dreaming tracks, songlines and areas of cultural significance".

However, Justice Charlesworth dismissed the claim the project's export pipeline would destroy Aboriginal 'songlines' deep in the ocean and was especially critical of the author of one of these reports, UWA associate professor of climate geoscience Mick O'Leary, who she said had mislead some of the plaintiffs in his report detailing the claimed location of the 'Crocodile Man' songline and the resting place of 'Ampitji' — otherwise known as the rainbow serpent.

"Dr O'Leary's admission was freely volunteered, such that he did not lie to the Court. But he did lie to the Tiwi Islanders, and I find that he did so because he wanted his 'cultural mapping' exercise to be used in a way that would stop the pipeline," she said.

"It is conduct far flung from proper scientific method and falls short of an expert's obligation to this Court."

The AFR reported on Wednesday Mr O'Leary was hired by the EDO, meeting with some Tiwi islanders over one day, with forty-one videos recorded - all of which were viewed by Justice Charlesworth.

In one video, an islander points to Cape Fourcroy - the westernmost tip of Bathurst island - and said it was the location of where Crocodile man entered the sea: seven km from the planned Santos pipeline. The islander is not told that at this point in history, Cape Fourcroy doesn't yet exist in its current form.

"At that time [of the last Ice Age - 26,000-20,000 years ago] the shoreline lay well seaward of where it is today," Justice Charlesworth said.

"The land masses now known as the Tiwi Islands did not exist as islands but rather formed a part of the mainland. The shoreline was located well north of the modern mainland shoreline, approximately 60 km south of the centre of what is now the Barossa Field."

In December, Justice Charlesworth asked Mr O'Leary about his understanding of the Crocodile man story, especially in relation to the mythical figures travelling from Cape Fourcroy - the westernmost tip of Bathurst island - to an ancient lake in the now Timor Sea. She asked how the Crocodile Man could have lived in a cape that didn't exist historically at the time claimed.

Mr O'Leary argued this was a "deep time" story; Crocodile Man inhabited an earlier and bigger Australia that existed before the emergence of islands like Bathurst, and nearby Melville, had risen from the sea.

However, Justice Charlesworth said she didn't understand how the then land-locked Cape Fourcroy could possibly be a sacred ground that Crocodile Man used when he would have hunted further west.

"I have drawn conclusions about the lack of integrity in some aspects of the cultural mapping exercise, which undermined my confidence in the whole of it," Justice Charlesworth said.

"As a consequence of that conclusion, I am not satisfied there is any risk of environmental impact of the kind asserted by the applicants in this part of the case, and it has therefore been unnecessary to consider whether any such risk should be characterised as 'significant' or 'new'".

Furthermore, she used her judgement to hypothesise that there was a real possibility ancient stories could be weaponised by any expert whose independence was dubious.

"The material supports an inference that Indigenous instructions have been distorted and manipulated before being presented to this Court via an expert report, and I so find," she wrote in her judgement.

Justice Charlesworth also reserved criticism for the EDO and their lawyer, who in video 39, implied the islanders' ancient home was surrounded by a giant, freshwater lake by drawing lines on maps.

"Most concerningly, I consider that Video 39 depicts what could only be described as the EDO lawyer drawing on the map in a way that could not on any reasonable view truthfully reflect what the Tiwi informant had said," she wrote.

"The content of Video 39 alone is sufficient to reduce the integrity and hence the reliability of the cultural mapping exercise to nought."

The Australian Financial Review (AFR) reported Mr O'Leary was still adamant that his work was factual.

"I still stand by the factual nature of the expert reports I wrote, which were based on transcripts of Tiwi interviews, and affidavits provided to me by the Environmental Defenders Office," he said.

In her findings, Justice Charlesworth said: "The evidence establishes nothing more than a negligible chance that there may be objects of archaeological value in the area of the pipeline route".

"I have reached that conclusion largely because I am not satisfied that the expert reports relied upon by the applicants can support the propositions for which they argued."

Mr Munkara told the ABC "This outcome is very disappointing".

"We brought this case to protect our Sea Country," he said. "I am a true believer for my Country. We are hurting and need some time to think."

National Indigenous Times contacted the Environmental Defenders Office for comment.