Amber Heard's surprise reference to Kate Moss on the stand last week, which prompted Johnny Depp's lawyers to erupt in glee, may spectacularly backfire, sources and experts told Fox News Digital.

The "Aquaman" actress told jurors May 5 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.  

Johnny Depp and Kate Moss

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

"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 supermodel, whom he dated in the 1990s, down a flight of stairs.

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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 smiled broadly. 

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. 

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.

US actress Amber Heard reacts as she testifies during the 50 million US dollar Depp vs Heard defamation trial at the Fairfax County Circuit Court in Fairfax, Virginia, USA, 05 May 2022. Johnny Depp's 50 million US dollar defamation lawsuit against Amber Heard that started on 10 April is expected to last five or six weeks.

Amber Heard testified on May 5, 2022, during Johnny Depp's defamation trial against her. (Jim Lo Scalzo/Pool Photo via AP)

Manhattan-based civil lawyer Roland Acevedo called the name-dropping of the supermodel an obvious misstep that could "blow up in her face." 

"It certainly could open the door to calling in Kate Moss," said 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."

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

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

The decision on whether Moss can or will testify ultimately rests with Judge Penney Azcarate. 

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A source close to Depp said he and Moss have remained close friends, and his legal team may reach out to her to testify during the "Pirates of the Caribbean" star's rebuttal case. 

Johnny Depp and Amber Heard

Johnny Depp and Amber Heard  (Evelyn Hockstein/Pool via AP)

Virginia-based civil lawyer Broderick Dunn agreed with Acevedo. "I think it's certainly something Johnny Depp's lawyers will now explore," he said. It wasn't just the Moss reference that may have landed Heard in hot water.  During Heard's testimony, she recounted the first time Depp allegedly hit her in 2013.

"I knew you can't hit a woman. I knew you can't hit a man," she testified. 

LONDON, UNITED KINGDOM - NOVEMBER 03: Johnny Depp and Amber Heard attend The UK Premiere of 'The Rum Diary' at on November 3, 2011 in London, England. (Photo by Stuart Wilson/Getty Images)

Actress Amber Heard slammed the accusation made from ex-husband Johnny Depp's camp. (Getty)

This statement may allow Depp's team to cross-examine Heard about her 2009 arrest for allegedly hitting ex-girlfriend Tasya van Ree at the Seattle-Tacoma International Airport. 

She was charged with misdemeanor domestic violence for allegedly yanking van Ree's necklace off and smacking her in the arm, but prosecutors declined to move forward with the case, according to Depp's lawsuit.

Dunn said the domestic violence incident could come in now. "If Amber Heard is saying she ‘knew she can’t hit a woman' and if she's been charged with doing just that, then it cracks the door open for Depp's team to try to introduce evidence of any prior assaults," said Dunn.

After Heard's mugshot surfaced, the actress allegedly claimed that she was arrested on a "trumped-up charge" because the cops were misogynistic and homophobic. 

The police officer who slapped her in cuffs "was both a woman and a lesbian activist, who publicly said so after she was publicly disparaged by Ms. Heard," Depp's lawyers wrote the suit.

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Acevedo added that "you can prep a witness until you're blue in the face" and these blunders still happen.

"They may have told her 10 times don’t bring up Kate Moss, but it gets emotional on the stand, and it's not easy to testify," he said.

The trial was on a pre-scheduled break this week but is set to resume on Monday with Heard back in the witness box.