The lawsuit in San Francisco federal court seeks unspecified damages from Musk, Tesla and its directors on behalf of investors who bought or sold Tesla stock in the days after Musk's announcement on Twitter.

U.S. District Judge Edward Chen, who is overseeing the trial, has ruled that those statements were false and that Musk made them recklessly. At trial, the jury will determine whether the statements mattered to investors and how they affected Tesla stock.

Trials are a rarity in shareholder class actions, with fewer than 1% being tried to verdict between 1997 and 2018, according to securities litigation consulting firm Cornerstone Research.

Musk, meanwhile, has unloaded quantities of Tesla stock to help finance his purchase of social media platform Twitter.