Rupert Murdoch rarely has to answer for the alternative realities presented by his hugely profitable US cable network, Fox News.

Its conspiratorial claims of a parade of cover ups from the 2012 Benghazi attack to the climate crisis and Covid-19 have been lapped up by Fox viewers and scorned by much of the rest of America, and then the world moved on. But on Tuesday, the 91-year-old billionaire media mogul will be obliged to answer difficult questions under oath about the inner workings of Fox.

Dominion Voting Systems is suing the cable news station and its Murdoch-owned parent company, Fox Corp, for $1.6bn (£1.3bn) over repeated claims that it rigged its voting machines as part of a conspiracy to steal the 2020 presidential election from Donald Trump.

The suit shines a spotlight on Fox News’ part in promoting Trump’s “stop the steal” campaign and its hand in driving the January 6 insurrection at the Capitol. But legal experts say that Dominion, which supplied voting machines to 28 states, appears to be building a wider case that Fox News has a long history of misinformation and steamrolling facts that do not fit its editorial line.

Over the past few months, Dominion’s lawyers have been working their way up the tree of Fox News producers, executives and presenters with interrogations under oath about the network’s work culture and its weeks of conspiratorial, and at times outlandish, claims about Trump’s defeat. On Monday, lawyers deposed Murdoch’s eldest son, presumed successor and Fox Corp CEO, Lachlan.

Now, Dominion has reached the top of the tree. Months of accumulated testimony are expected to put Murdoch, the chair of Fox Corp, in the difficult position of either having to deny he has control over what happens at his most influential US news operation or defend its campaign to promote the biggest lie in US electoral history.

Murdoch is already grappling with the costly legacy of phone hacking by British newspapers the News of the World and the Sun. His UK company has paid more than £1bn ($1.2bn) over the past decade to keep the gruesome details from being heard in open court with no end in sight after a high court judge earlier this year refused to prevent the filing of new claims.

When Murdoch was called to give evidence to a UK parliamentary hearing in 2011 about News of the World hacking the phones of a murdered schoolgirl as well as hundreds of politicians, celebrities and other public figures, he said that it was the most humble day of his life. He also claimed to have known nothing about the wrongdoing and said that he had been misled.

“I feel that people I trusted … I’m not saying who … let me down and I think they behaved disgracefully,” he told parliament. “And it’s time for them to pay.”

But he can make no such claim about Fox News, where its misrepresentations were on full display. So far, the only people to pay at the network are the ones who got it right.

The trouble started on election night after Fox called the key swing state of Arizona for Joe Biden. The call drew Trump’s ire and unleashed a backlash against the network from his supporters.

At that point, Fox News CEO Suzanne Scott warned against bowing to pressure to embrace an alternate reality and reverse the Arizona call.

“We can’t give the crazies an inch,” she said, according to court records.

As it turned out, “the crazies” took a mile, as Fox News put a parade of Trump lawyers, advisers and apologists front and centre over the following weeks to promote a myriad of conspiracy theories about how the election was stolen from Trump, including by rigging the voting machines.

Alongside them, some of Fox’s biggest names took up the cry of fraud. NPR revealed that during the discovery process, Dominion acquired an email written by a Fox News producer begging colleagues not to allow one of those presenters, Jeanine Pirro, on the air because she was spreading conspiracy theories about the vote. Pirro, a former district attorney and judge who is close to Trump, continued broadcasting.

Lawyers have also obtained rafts of internal messages that are “evidence that Fox knew the lies it was broadcasting about Dominion were false” and part of a culture of politically loaded reporting and broadcasts far from the network’s claim to be “fair and balanced”.

Dominion claims that without Fox, “these fictions” about electoral fraud would never have gained the same traction among large number of Americans.

“Fox took a small flame and turned it into a forest fire,” the company claims in its lawsuit.

In August, lawyers questioned another presenter, Sean Hannity, who has been described as “part of Trump’s campaign apparatus”. He was grilled for more than seven hours including about a broadcast two weeks after the presidential election in which Trump lawyer and conspiracy theorist Sidney Powell was a guest.

Powell claimed that Dominion “ran an algorithm that shaved off votes from Trump and awarded them to Biden”. She said the company “used the machines to inject and add massive quantities of votes for Mr Biden”. Powell has also claimed that Dominion used software developed to help the late Venezuelan leader Hugo Chávez steal elections.

Dominion has said that it warned Fox News that such claims were false but that it continued to air them in an attempt to assuage Trump supporters out of concern they would move to other right-wing broadcasters.

“It’s an orchestrated effort,” Dominion’s lawyer told a court hearing. “It’s not just on the part of each host individually, but it’s across Fox News as a company.”

So far the only Fox employees to pay a price for the debacle are those who got it right. Weeks after the election, the network fired its political director, Chris Stirewalt, who had infuriated Trump and other Republicans by refusing to back down from calling Arizona for Biden. The Washington managing editor, Bill Sammon, who supported Stirewalt’s decision, took retirement.

Fox argues that Hannity and the other presenters are protected by journalistic privilege but that position has been complicated by the Fox host’s own description of his role.

In defending his overt bias in favour of Trump and Republicans, Hannity has more than once said he is not a journalist but a talk show host, and so does not have to adhere to the profession’s ethical standards. He took the same position earlier this year after the January 6 congressional committee exposed dozens of his messages to Trump’s chief of staff, Mark Meadows, offering advice and seeking direction as the White House challenged the presidential election result.