Elon Musk, the billionaire boss of Tesla and SpaceX, emerged victorious this weekend from his defamation trial as a US federal court jury swiftly rejected a $190m (€172m) claim brought against him by a British cave explorer whom Musk had branded a "paedo guy" on Twitter.

The unanimous verdict was returned after roughly 45 minutes of deliberation on the fourth day of Musk's trial. Legal experts believe it was the first major defamation lawsuit brought by a private individual over remarks on Twitter to be decided by a jury.  

Cave explorer Vernon Unsworth helped rescue a boys' soccer team from a flooded cave in Thailand - and during a TV interview he criticised Musk's "PR stunt" of showing up at the site with a mini-submersible, which was never used. Musk responded with several tweets to his almost 30m followers and a damaging email to a news outlet, and the lawsuit followed.

Musk defended his comments as trivial taunts made on a social media platform that he argued everyone views as a world of unfiltered opinion, which is protected as free speech, rather than statements of fact.

"I think this verdict reflects that there is a feeling that internet tweets and chats are more like casual conversation whether you call it opinion or rhetoric or hyperbole and should not be punished in a lawsuit," said one defamation specialist.

Several other lawyers, who specialise in defamation, privately expressed surprise at the outcome of what they viewed as a strong case for the cave explorer.

They attributed it to Musk's fame and the perceived youthfulness of the jury. But they also agreed it would shift the legal landscape, undercutting the cases that would have seemed viable before the trial while defendants would use it to try to reduce possible settlement values.

Musk's court papers cast his comments as part of the rough-and-tumble world of Twitter, which rewards and encourages emotional outbursts and sucks in readers worldwide but that no one takes seriously.

While Musk was cleared of liability, the trial was just the latest incident where he has faced legal problems because of troublesome tweets.

Musk and Tesla reached a $40m (€36m) settlement with the Securities and Exchange Commission (SEC) last year over claims he misled investors with a tweet declaring he had secured financing to buy out the electric car maker. Earlier this year, the SEC sought to hold him in contempt of court for tweeting a misleading projection of how many cars Tesla would make. That led to a new agreement imposing tight controls on Musk's tweets about the company.

The day after Musk's tweet about Unsworth, Tesla's stock price fell 3pc and shareholders and people within the company were urging him to apologise. Musk said he resisted at first because he didn't want to look "foolish and craven" by doing so right after the stock dropped.

In recent years, judges have been wrestling with social media comments and whether to consider them factual statements or protected opinions.

US President Donald Trump, singer and actress Courtney Love and actor James Woods have all been embroiled in multiple libel lawsuits over tweets, with mixed results.

Trump has had success casting Twitter as a place where combatants trade demeaning messages that users understand are not defamatory statements of fact.

A judge dismissed a case against the president for a tweet blasting as a "total con job" a claim by adult film actress Stormy Daniels that she was threatened for speaking about an alleged affair with Trump.

The judge described Trump's message as "rhetorical hyperbole", fired off with an incredulous tone that no reasonable person would take as factual statement about Daniels, whose real name is Stephanie Clifford.

©Associated Press