US law experts say Donald Trump faces significant hurdles in his $10 billion case against Rupert Murdoch's Wall Street Journal over reports he sent a birthday message to Jeffrey Epstein with a sexually suggestive drawing.
The lawsuit, filed in the Florida Supreme Court, claims the Wall Street Journal "failed to show proof that President Trump authored or signed any such letter and failed to explain how this letter was obtained".
But experts say defamation cases, brought forward by public figures, are notoriously hard to prove in the US, and they rarely make it to a jury.
The paper has said it was prepared to "vigorously" defend its journalism.
If the case does go to trial, Mr Trump may be forced to provide information about the nature of his relationship with the convicted paedophile and billionaire, and the Journal may be asked to show how it obtained the letter or proved its existence.
So, how likely is it Mr Trump will get his day in court?
How do you prove defamation in the US?
Winning or settling a defamation case in the US can be difficult, mostly due to the Supreme Court's interpretation of the First Amendment in the US Constitution.
The First Amendment protects freedom of speech, religion, press, assembly, and petition.
It is even more difficult for a public figure like Donald Trump to win a defamation lawsuit, said Harry Melkonian, a media lawyer and honorary associate at the United States Studies Centre.
"It is extremely difficult and intentionally made so for public figures to bring defamation claims in the US," he said.
"By definition, the US president is the most public of public figures."
Shawn Trier, a constitutional law expert at Australian National University, agreed.
"A case in the early 1960s during the civil rights movement found that even if you have factual information that's incorrect, unless you prove a term called actual malice — that you knew it was wrong or didn't care — it would be really hard for that to be proven," he said.
Actual malice is knowledge that the material published was false, or reckless disregard of whether it was false or not.
"In the case of the Wall Street Journal, it would literally have to be the case that they knew the letter was false or knew it didn't exist or they had a really good reason to suspect it was forged but ignored it," Dr Tier said.
Dr Melkonian said the Supreme Court set this standard for public figures to prevent self-censorship by the media.
"They also felt that public figures are pretty well equipped to respond publicly to undo any harm, and Trump can get on TV any night and say this story is false, they made it up," he said.
"So when you combine all those things, it makes for an extremely difficult case, and quite honestly, I've read the complaint and I think they will have difficulties even getting this complaint to court."
What will Donald Trump have to prove?
In Australia, defamation law is "relatively straightforward", Dr Melkonian said.
If a publisher prints something that a person says isn't true, the publisher must prove on the balance of probabilities that it is.
But American law is the opposite, Dr Melkonian said; the public figure has to prove the story is false.
"Trump has to prove they either knew it was false or they harboured serious doubts and did it anyway," Dr Melkonian said.
"And he has to prove that by an exaggerated standard of proof."
But US courts rarely find that actual malice exists, and there has only been one case, which was between Time Magazine and the Israeli defence minister in 1984.
Court documents show that Mr Trump will argue that such a letter did not exist and the two journalists who wrote the story "possessed information and had access to information that showed their statements were false."
It does not say, however, what that information was.
"The mere fact that he told them 'it's false' before they printed it isn't enough because if that was, you could stop anything from being printed," Dr Melkonian said.
From the legal documents, it appears Mr Trump will also argue that the circulation of the story created further damage to his reputation.
"And given the timing of the defendants' article, which shows their malicious intent behind it, the overwhelming financial and reputational harm suffered by President Trump will continue to multiply," the court documents said.
But Dr Melkonian said, "he's already said it's false, and he certainly has made more publicity saying it's false than the Wall Street Journal got with the article."
Why is he pursuing the case?
Dr Melkonian said public figures sometimes took steps like Mr Trump's to "make it clear to the public that they believe the article is a falsehood".
"Donald Trump has gotten a lot of publicity out of filing this case, and that may be the vindication that he wants now the public knows he is taking it to court to prove he didn't do it," he said.
A $10 billion award would be the largest finding of defamation damages in history, dwarfing already-massive cases in recent US proceedings.
These include a $1.5 billion judgement against conspiracy theorist Alex Jones, and Fox News's settlement with Dominion Voting Systems for $787.5 million.
"It's unlikely he has a legal case against the Wall Street Journal, but it probably helped him politically," Dr Trier said.
"He likes to do this a lot, to say 'look how I've been treated, it's so bad I'm suing.'"
What does the Wall Street Journal say?
The Wall Street Journal has indicated it will defend itself.
"We have full confidence in the rigour and accuracy of our reporting, and will vigorously defend against any lawsuit," a spokesperson for publisher Dow Jones said in a statement.
Yesterday, the White House removed the Wall Street Journal from the pool of reporters covering Trump's upcoming weekend trip to Scotland.
"As the appeals court confirmed, the Wall Street Journal or any other news outlet are not guaranteed special access to cover President Trump in the Oval Office, aboard Air Force One, and in his private workspaces," White House Press Secretary Karoline Leavitt said in a statement to various US media outlets.
"Due to the Wall Street Journal's fake and defamatory conduct, they will not be one of the 13 outlets on board. Every news organisation in the entire world wishes to cover President Trump, and the White House has taken significant steps to include as many voices as possible."
While the Murdoch-owned media company has the power to fight such a case, many do not.
"It could have an insidious effect on journalism and free speech," Dr Trier said.
"There should be early dismissals [in defamation cases like these], but there are still costs, and smaller organisations that get threats like this are more likely to back down.
"It raises a lot of concerns, and Trump has been very unique in using his office to carry out these retributions against the media."
