Supermodel Kate Moss will testify Wednesday on behalf of Johnny Depp about a staircase rumor in his bombshell defamation trial against Amber Heard, a source close to the actor told Fox News Digital.

Moss, 48, is expected to testify via live video link, the source said. The cat walker and Depp, who dated in the 90s, have remained good friends the source said. 

Kate Moss

British model Kate Moss poses during the launch of the new Mango 2012 collection in London January 24, 2012. (Reuters)

Moss got dragged into the case May 5 when Heard told jurors the only time she had ever "landed a blow" was during a fight with Depp over his alleged infidelity in March 2015, when she thought he was about to push her sister down the stairs.  

"I don't hesitate. I don't wait. I instantly think of Kate Moss and the stairs, and I swung at him," Heard blurted, referring to a rumor that Depp had once shoved the British icon down the stairs.

JOHNNY DEPP EXPECTED BACK ON THE STAND MONDAY IN HIS DEFAMATION TRIAL AGAINST EX-WIFE AMBER HEARD

Depp's attorney Ben Chew opened his mouth widely and his eyes lit up in an expression of giddy surprise, as he turned to his team and did a fist pump. 

Depp, sitting next to Chew, looked down at the plaintiff's table and grinned.

Johnny Depp and Kate Moss

Johnny Depp and Kate Moss, who dated in the 1990s. (Ron Galella, Ltd. via Getty Images)

Legal experts previously told Fox News Digital that Heard's statement could open the door to allowing Depp's team to call Moss to refute the staircase claim.

AMBER HEARD'S REFERENCE TO JOHNNY DEPP'S EX KATE MOSS MAY ‘BLOW UP IN HER FACE,’ EXPERT SAYS

"It certainly could open the door," said New York City-based civil lawyer Roland Acevedo. "It’s considered a tangential issue that usually courts don’t let you bring in but since the defense opened the door and said he did this, they now may be able to call her to prove it never happened. This could blow up in her face."

Johnny Depp Amber Heard

A photo combination of Amber Heard and Johnny Depp in court May 23, 2022. (AP Photo/Steve Helber, Pool)

Depp is also expected back on the stand Wednesday as a rebuttal witness in his own case. 

Depp is suing Heard for $50 million in Fairfax County Circuit Court in Virginia over a 2018 op-ed she wrote identifying herself as a victim of domestic abuse, which he says ruined his reputation and career. 

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In a $100-million countersuit, Heard alleges that her ex-husband conspired with his former attorney to defame her by calling her abuse allegations a hoax.