Pauline Hanson's lawyers have shared a judge's concern over an expert witness sought by Mehreen Faruqi's team in a legal battle between two senators over racial discrimination and free speech.
Senator Faruqi sued over a September tweet by Senator Hanson, who wrote she should "pack (her) bags and piss off back to Pakistan".
Senator Hanson's tweet came in response to Senator Faruqi's following the death of Queen Elizabeth II.
She wrote she could not mourn the passing of the leader of a "racist empire built on stolen lives, land and wealth of colonised peoples".
The Greens deputy leader is seeking $150,000 from Senator Hanson in the lawsuit, claiming the tweet breached the Racial Discrimination Act by insulting, offending, humiliating and intimidating herself and others with Pakistani backgrounds.
Senator Faruqi's barrister Jessie Taylor told the Federal Court on Thursday five days should be enough to hear the issue, when she will seek to call three expert witnesses, including one sparking concern from the other parties and the bench.
In addition to evidence from an expert on "race rhetoric" and another on social psychology who can speak to the tweet's likely impact, Ms Taylor proposes to call an expert on the relationship between freedom of speech and hate speech.
"Those are matters which have attracted significant, enormous volumes of academic consideration," Ms Taylor said.
She said that expert will be carefully selected when Justice Angus Stewart questioned the admissibility of their evidence, preferring legal consideration rather than academic.
"I've got books on freedom of speech but they were written by a law professor," he said.
Hanson's high-profile barrister Sue Chrysanthou SC was also surprised by the third proposed expert.
"It seems to us there are seven experts and they're sitting on the High Court," she said.
Ms Chrysanthou has raised with Senator Faruqi's team that its concise statement of claim falls short and has not adequately addressed what the case is about, she said.
"We're concerned the evidence my learned friend has foreshadowed travels well beyond what would be allowed," she said.
Ms Taylor said the yet-to-be identified expert will give evidence on the tweet's impact on the broader community, potentially circumventing public interest protections in the act.
"It's not going to be a matter of inviting anyone and everyone to give an opinion on that," she said.
Justice Stewart has ordered a trial to begin on April 29, with the discussed expert evidence to be confirmed by the end of September and Senator Hanson's lawyers to respond by December 22.
He also gave any attorneys-general until the end of January to intervene in the case among other orders.
