Documents in the case in Delaware State Court show Murdoch and other Fox executives believed Joe Biden fairly beat Donald Trump and that the results were not in doubt.

The acknowledgement by Murdoch is included in a filing on Monday from Dominion Voting Systems, as part of the voting technology firm’s $US1.6 billion ($A2.4 billion) defamation lawsuit against Fox News and parent company Fox Corp over Fox’s coverage of the 2020 presidential election.

A five-week trial is scheduled to begin on April 17.

Murdoch’s testimony is part of his deposition in the lawsuit, the entirety of which Reuters has not viewed because it remains under seal.

Dominion has argued that internal communications and depositions by Fox personnel prove the network knowingly spread falsehoods about Trump’s loss in the 2020 US presidential election in order to bolster its ratings.

Fox has argued that its coverage of claims by Trump’s lawyers were inherently newsworthy and protected by the First Amendment of the US Constitution.

“Executives at all levels of Fox – both (Fox News Network) and (Fox Corporation) – knowingly opened Fox’s airwaves to false conspiracy theories about Dominion,” Dominion wrote in its filing.

Asked by a Dominion lawyer if some of Fox’s commentators had endorsed the idea that the 2020 election was stolen, Murdoch responded, “Yes. They endorsed,” according to the filing.

The latest filing by Dominion opposes Fox’s motion for summary judgment, which sought a ruling in the media company’s favour that would pre-empt the need for a trial on certain legal issues.

In its own filing made public on Monday, Fox argued that its coverage of statements by Trump and his lawyers were inherently newsworthy and that Dominion’s “extreme” interpretation of defamation law would “stop the media in its tracks”.

“Under Dominion’s approach, if the president falsely accused the vice president of plotting to assassinate him, the press would be liable for reporting the newsworthy allegation so long as someone in the newsroom thought it was ludicrous,” Fox said.

Dominion sued Fox News Networks and parent company Fox Corp in March 2021 and November 2021 in Delaware Superior Court, alleging the cable TV network amplified false claims that Dominion voting machines were used to rig the 2020 election against Trump, a Republican who lost to Democratic rival Biden.

In a statement on Monday, a Fox spokesman said Dominion’s view of defamation law “would prevent journalists from basic reporting and their efforts to publicly smear Fox for covering and commenting on allegations by a sitting president of the United States should be recognised for what it is: a blatant violation of the First Amendment.”

Dominion’s motion for summary judgment was replete with emails and statements in which Rupert Murdoch and other top Fox executives say the claims made about Dominion on-air were false – part of the voting machine company’s effort to prove the network either knew the statements it aired were false or recklessly disregarded their accuracy.

That is the standard of “actual malice,” which public figures must prove to prevail in a defamation case.

-AAP