A California jury has tossed out Elon Musk's high-profile lawsuit against OpenAI and its boss Sam Altman.
In a unanimous verdict, the jury agreed that Musk had waited too long to file his lawsuit, leaving all of his claims essentially expired.
Musk had accused Altman of breaching a non-profit contract by shifting the ChatGPT-maker to a for-profit company after Musk donated $38m (£28.5m) early in OpenAI's history.
Musk claimed Altman had deceived him by accepting his money and then reneging on OpenAI's original non-profit mission to develop artificial intelligence (AI) technology for the benefit of humanity.
Jurors spent just about two hours on Monday deliberating on the case, but they had spent three weeks viewing internal correspondence and hearing testimony from Musk, Altman and other tech industry executives, such as Microsoft's chief executive Satya Nadella.
Musk had accused Microsoft of aiding and abetting OpenAI in its allegedly improper transition to a more for-profit company.
Musk's other claims against Microsoft were dismissed as a matter of law given the jury's findings on the two claims against OpenAI.
A spokesperson for Microsoft said of the verdict: "The facts and the timeline in this case have long been clear."
The company added that it remained committed to its work with OpenAI.
The jury's decision adds to a string of recent losses and settlements for Musk in court.
Within a few hours of the verdict, Musk criticised the decision against him in the OpenAI case, writing on X that it created "a free license to loot charities if you can keep the looting quiet for a few years!"
He also accused the judge overseeing the case of being a "terrible activist" who used the jury "as a fig leaf."
In another post to X, Musk vowed to file an appeal, claiming that the jury did not decide "on the merits of the case" and that the decision was based on a "calendar technicality".
As the jury found that the statue of limitations, a set timeframe for when legal accusations need to be made in order to be considered, had lapsed for Musk's claims of breach of charitable trust and unjust enrichment, the jury was not required to consider the merits of his claims.
Carl Tobias, a law professor at the University of Richmond School of Law, said that the jurors had made a "very fact-based decision" about the case.
"This case seemed kind of weird and crazy, but this is why we trust juries, because they bring the common sense of the community to resolve factual disputes," Tobias said.
On the trial's first day, Musk took the stand wearing a dark suit and tie and was asked by one of his lawyers what the legal action was about.
"It's actually very simple," he said. "It's not OK to steal a charity... If it's okay to loot a charity, the entire foundation of charitable giving will be destroyed."
Altman told the jury during his own testimony that Musk not only backed the idea of OpenAI becoming a for-profit business, he had vied for control of it for the long-run.
"A particularly hair-raising moment was when my co-founders asked, 'If you have control, what happens when you die?'" Altman recalled in court. "He said something like, 'maybe it should pass to my children.'"
The pair started OpenAI in 2015, but Musk left in 2018 after his co-founders denied him control.
The lawsuit was in some ways a culmination of the animosity between Musk and Altman built up since then.
As Altman became one of the most famous and wealthy names in the tech industry after the explosive success of ChatGPT, Musk began to criticise Altman and OpenAI.
In 2024, the company felt compelled by Musk's online claims to publish a lengthy blog post, offering the public a timeline of events seeking to refute Musk's claims.
On Monday, Sam Singer, a spokesman for OpenAI, said from outside the Oakland courthouse that the verdict was a "tremendous victory".
"This was nothing but an effort by Mr Musk to slow down a competitor," he said, adding that it was a victory "for the justice system as well".
Lawyer William Savitt, who represented OpenAI during the trial, said Musk's lawsuit "bears no relationship with reality" and that the jury decided that Musk was lying during his testimony about the company's origins.
"We're pleased that the jury reached the right result, and reached it quickly," he said.
Savitt also said that OpenAI would continue to focus on its mission to develop "safe AI for the benefit of all humanity".
Outside court, Marc Toberoff, a lawyer for Musk, said: "This war is not over, and I'd sum it up in one word: appeal."
Such a move would mean that a complete resolution of the case could end up "being dragged out for a while", according to Tobias of the University of Richmond.
But Musk may be unlikely to win there, too.
"The bottom line is that an appeals court would be very unlikely to overturn such a fact-specific decision from a jury, and a judge who agreed with it," Tobias said.
Raffi Melkonian, an appellate lawyer who has argued before the US Supreme Court and is a partner at Wright, Close, Barger & Guzman LLP, wrote online of Musk's plans to challenge the outcome: "Appeals of jury verdicts are very hard to win."
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