((This December 6 story is refiled to fix typo in quote in paragraph nine))
By Tom Hals
(Reuters) - Elon Musk's daring has left its mark on electric cars and rockets, and now experts say the entrepreneur may have reshaped U.S. defamation law with his willingness to defend at a high-stakes trial a lawsuit over an off-the-cuff tweet.
The victory by Tesla Inc's outspoken chief executive over a Twitter message describing a British cave explorer as "pedo guy" has raised the bar for what amounts to libel online, according to some legal experts.
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 Chip Babcock, a lawyer who defends against defamation lawsuits.
Several other attorneys who specialize in defamation cases privately expressed surprise at the outcome of what they viewed as a strong case for the cave explorer, Vernon Unsworth. 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.
Mark Sableman, a lawyer who defends defamation cases, said the freewheeling nature of social media has inevitably changed the understanding of language and what amounts to defamatory factual statements, versus opinion.
"I think defendants in modern defamation cases are likely to point to the vitriolic no-holds-barred nature of modern social media, cable TV, and political discourse, in contending that many words and accusations formerly considered defamatory are now understood only as mere opinions, not factual assertions," he said.
In general, to prove libel, the written form of defamation, someone must show the existence of a false statement, which defendants often try to present as opinion. The plaintiff also must show it was published to a third party, it was negligent and it caused harm.
"While there is more leeway and more hyperbole online and in social media in general, courts never really accepted that argument that social media is a libel free-zone," said Lyrissa Lidsky, a professor who specializes in defamation at the University of Missouri School of Law.