"He will not be testifying," Musk's attorney Alex Spiro confirmed to NBC News on April 27.
The billionaire was originally listed as potential witness for Heard in pre-trial filings for the case, in which Depp is suing heard for $50 million. (Heard is countersuing him for $100 million.) Heard and Depp are accusing each other of violence during their one year of marriage; each party denies the allegations.
Heard, 36, dated Musk for nearly a year following her divorce from Depp, 58, in January 2016. The actress and the entrepreneur reportedly first met on the set of Robert Rodriguez's Machete Kills in 2013; Heard was the lead in the film and Musk had a cameo appearance.
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The Hollywood Reporter initially reported that Musk became "infatuated" with Heard and began emailing Rodriguez and his team to set up dinners and lunches with her.
"If there is a party or event with Amber, I'd be interested in meeting her just out of curiosity," Musk wrote in one of the emails, made available to THR through a confidential source. "Allegedly, she is a fan of George Orwell and Ayn Rand. Most unusual."
After splitting from Depp, Heard's relationship with Musk -- who filed for divorce from "Westworld" actress Talulah Riley in early 2015 -- turned romantic. The couple went Instagram official in April 2017, when Heard shared a pic of the two at an event showing Musk looking away from the camera with a lipstick mark on his cheek, while Heard posed for the camera.
By the summer of 2017, the couple announced that they had broken up.
"Although Amber and I did break up, we are still friends, remain close and love one another," Musk wrote on Instagram that August. "Long distance relationships when both partners have intense work obligations are always difficult, but who knows what the future holds."
Hours later, Heard confirmed the split with her own Instagram post, "Being in the public eye means having to explain yourself to so many people, so much of the time. In this case, I'd like to remain more quiet. Although we have broken up, Elon and I care deeply for one another and remain close."
Musk, 50, took the breakup hard, telling Rolling Stone in July 2017 he "was really in love" with Heard.
"It hurt really bad," he told the outlet in July 2017. "She broke up with me more than I broke up with her, I think."
He continued, "I've been in severe emotional pain for the last few weeks. Severe. If I'm not in love, if I'm not with a long-term companion, I cannot be happy, I will never be happy without having someone."
In December 2017, the couple seemed to give their relationship another shot when they were photographed kissing in Los Angeles and vacationing together in Chile, although an insider at the time told E! News, "They are not dating."
Musk became a prominent figure during Depp's unsuccessful U.K. libel case against a tabloid, when the actor accused the entrepreneur of having an affair with Heard while she was still married to him.
"Elon and Amber didn't start seeing each other until May 2016, and even then it was infrequent," a rep for Musk told E! News in March, "Their relationship didn't become romantic until some time later."