In July, the Tesla CEO called Vernon Unsworth, who assisted in the rescue, a " " on Twitter after the diver criticized Musk's proposed submarine rescue plan. Unsworth in September for defamation.
In a court order filed Friday, US District Judge Stephen Wilson denied Musk's attempt to dismiss the defamation case and set a trail date for Oct. 22. The Verge earlier reported on the court order.
"The significance of the ruling is clear: publication of accusations on Twitter does not provide a safe harbor for defamatory statements that are false and convey that they are factual," said L. Lin Wood, Unsworth's attorney, in an emailed statement Friday.
Musk's lawyers had argued that statements made on "unmoderated internet forums" like Twitter are considered opinion because "internet speech is unique," according to the court order.
Wilson rejected those arguments. The judge pointed to an email Musk sent to BuzzFeed, in which he told a reporter to "stop defending child rapists" and made an unsubstantiated claim that Unsworth moved to Thailand to marry a 12-year-old child bride, according to the court order.
"There is nothing about the context in which [Musk ]made the statements...that would create doubt as to whether [Musk's] statements implied assertions of objective fact," Wilson wrote.
The judge also pointed to the fact that Musk followed up with his initial tweet about Unsworth by adding "Bet ya a signed dollar it's true," indicating he believed the veracity of his statement.
Tesla didn't immediately respond to a request for comment.
You can read the court document below: