San Francisco, Dec 4

Multi-billionaire tech mogul Elon Musk made his first courtroom appearance as a defendant in a defamation case brought against him by Vernon Unsworth, a British man over "pedo guy" tweet, said Unsworth had insulted him, so he insulted him back.

"This is a case about insults between two men," said Musk's attorney, Alex Spiro, in his opening statement to the jury in a federal courthouse in Los Angeles on the first day of t

he trial, BBC reported on Wednesday.

Musk said the "pedo guy" tweet was not meant to be taken literally.

The Tesla co-founder filed a declaration that "pedo guy" is a common insult in South Africa used to insult demeanor and appearances.

He elaborated by saying, "It's quite common in the English speaking world. Calling someone a 'pedo guy' means creepy. If you did a search or asked someone what it means it would be a creepy."

Tesla CEO apologised directly to the cave diver in court, looking directly at him.

"I apologised in a tweet and again in the deposition, and I'll say it again - I apologise to Mr Unsworth," he said.

Meanwhile, Lawyers for Unsworth argued that Musk was using his social media platform to damage the explorer's reputation and paint him as a pedophile.

Last year, twelve boys and their coach were trapped in the Tham Luang cave complex, were rescued after a week-long intense drama.

Musk offered to assist the rescue mission by providing a submarine but the request was turned down on the ground that it would be unworkable.

Unsworth took on Musk in a widely-shared interview, saying the "mini-sub" "just had absolutely no chance of working".

In response, Musk tweeted several things, now-deleted, "Sorry pedo guy, you really did ask for it."

Then, a month later, he called Unsworth a "child rapist" in an email.

Unsworth sued two months later in a Los Angeles federal court, saying Mr Musk falsely branded him a paedophile and child rapist.

Musk defends 'pedo guy' tweet in defamation trial