Technology billionaire Elon Musk has been found not liable in a defamation case involving a British cave explorer, saying outside court his “faith in humanity has been restored”.

In a case believed to be the first major defamation lawsuit by a private individual to go to trial over tweets, the verdict was delivered on day four of the trial on Friday, a short time after the case was handed to the jury of five women and three men.

The plaintiff, Vernon Unsworth, was seeking $US190 million ($277 million) damages against Mr Musk for calling him “sus” and a “pedo guy” on Twitter in a spat following the July 2018 Thai cave rescue.

During the trial, Mr Musk estimated his net worth at $US20 billion ($29 billion).

Mr Unsworth’s attorney L Lin Wood summed up his case against Mr Musk by calling the entrepreneur a “billionaire bully” who “dropped a nuclear bomb” on Mr Unsworth in a series of tweets suggesting he was a pedophile.

Mr Wood said Mr Musk’s “pedo guy” remark was a slur that would overshadow Mr Unsworth’s relationships and job prospects for years to come and urged jurors to teach the Tesla chief executive and SpaceX founder a lesson.

But the jury, in its unanimous decision, was apparently swayed by the arguments put forth by Mr Musk’s attorney, Alex Spiro, who said the Twitter message in question arose from an argument between two men and amounted to an off-hand insult that no one could be expected to take seriously.

“In arguments you insult people,” he said. “There is no bomb. No bomb went off.”

Tesla CEO Elon Musk at the US District Court on December 4.

The court heard Mr Unsworth was left “humiliated, ashamed, dirtied,” by the tweet from the billionaire but lawyers on behalf of Mr Musk argued it was no more than a playground insult and did not represent an allegation of pedophilia.

In September last year, Mr Unsworth, who helped in the rescue of 12 boys and their coach from the Thai cave, launched the defamation lawsuit, demanding Mr Musk pay for making “heinous accusations” that he was a pedophile on social media following the rescue of the Wild Boars soccer team in July.

Mr Musk launched a Twitter tirade against the cave expert after the Briton, who lives in Thailand, earlier criticised his prototype submarine rescue plan in a television interview. 

Mr Musk and SpaceX engineers built a small submarine and shipped it to Thailand to help with the rescue.

The device wasn’t used, and Mr Unsworth called it a “PR stunt”.

In a post to Twitter on July 15 last year, Mr Musk said “sorry pedo guy, you really did ask for it”.

Later, Mr Musk accused Mr Unsworth of moving to Thailand to be with a bride who was about 12 years old.

Mr Musk eventually deleted his ‘pedo’ tweets and was forced to apologise after receiving massive backlash for the comments.

But according to the lawsuit, Mr Musk allegedly damaged his reputation ““by publishing false and heinous accusations of criminality against him to the public.”

These comment were “spoken in anger”, the lawsuit alleged.

According to the lawsuit, Mr Unsworth has a “significant other” in Thailand, a 40-year-old woman with whom he shares a house.

He first started travelling to Thailand in 2011, where he explored and mapped caves, the documents stated.

Not enough evidence

Jury foreman Joshua Jones said the panel found Mr Unsworth’s lawyers spent too much time trying to appeal to their emotions and not concentrating on the evidence, according to The Associated Press.

“The failure probably happened because they didn’t focus on the tweets,” Mr Jones said after the verdict was announced, reported AP.

“I think they tried to get our emotions involved in it. In a court of law you have to prove your case, which they did not prove.”

In the court, Mr Spiro mocked Mr Unsworth’s claims that he had been shamed and humiliated and that the tweet effectively sentenced him to a life sentence without parole, according to AP.

Mr Spiro said Mr Unsworth was honored by the Queen of England, the King of Thailand, had his photo taken next to former British PM Theresa May and was asked to speak at schools and contribute to a children’s book, which showed that no one took Musk’s insult seriously.

“People accused of pedophilia don’t get celebrated by world leaders,” Mr Spiro said.

“Kings and queens and prime ministers don’t stand next to pedophiles,”

-with AAP