"Sidney Powell is lying," about having evidence for election fraud, Tucker Carlson told a producer about the lawyer on November 16, 2020, according to an excerpt from an exhibit that remains under seal.
The internal communication was included in a redacted summary judgment brief filed on Thursday by lawyers for Dominion Voting Systems.
Carlson also referred to Powell in a text as an "unguided missile" and "dangerous as hell". Fellow host Laura Ingraham, meanwhile, told Carlson that Powell is "a complete nut. No one will work with her. Ditto with Rudy," referring to former New York mayor and Trump supporter Rudy Giuliani.
Sean Hannity, meanwhile, said in a deposition "that whole narrative that Sidney was pushing, I did not believe it for one second", according to Dominion's filing.
Denver-based Dominion, which sells electronic voting hardware and software, is suing both Fox News and parent company Fox Corporation.
Dominion said some Fox News employees deliberately amplified false claims that Dominion had changed votes in the 2020 election, and that Fox provided a platform for guests to make false and defamatory statements.
Lawyers for the cable news giant argued in a counterclaim unsealed on Thursday the lawsuit is an assault on the constitutional right to free speech.
They said Dominion had advanced "novel defamation theories" and was seeking a "staggering" damage figure aimed at generating headlines, chilling protected speech and enriching Dominion's private equity owner, Staple Street Capital Partners.
Fox lawyers also said in their own summary judgment brief that Carlson repeatedly questioned Powell's claims in his broadcasts.
Fox lawyers say Dominion's own public relations firm expressed scepticism in December 2020 as to whether the network's coverage was defamatory.
In their counterclaim, Fox lawyers wrote that when voting-technology companies denied the allegations being made by Trump and his surrogates, Fox News aired those denials, while some Fox News hosts offered protected opinion commentary about Trump's allegations.
Superior Court Judge Eric Davis is scheduled to preside over a trial beginning in mid-April, but granting summary judgment would obviate the need for a jury trial that could stretch over five weeks.
In its 192-page brief, Dominion said the judge should rule in its favour because "no reasonable juror could find in Fox's favour on each element of Dominion's defamation claim".
Dominion lawyers also assert that no reasonable juror could find in favour of Fox's "neutral reportage" and "fair report" defences.
Fox News lawyers argue the network's coverage and commentary are not defamatory.
Davis ruled last month that, for the purposes of the defamation claims, he will consider Dominion to be a public figure, meaning Dominion must prove by a preponderance of the evidence that the Fox defendants acted with actual malice or reckless disregard for the truth.
