Explainer: What Johnny Depp and Amber Heard have to do to win defamation trial

With the jury deliberating the outcome of the Johnny Depp-Amber Heard defamation trial, a New Zealand lawyer has explained what each side needed to do to win their case. 

Depp, 58, the 'Pirates of the Caribbean' star, sued ex-wife Heard for NZ$76 million and argued she defamed him when she called herself "a public figure representing domestic abuse" in an opinion piece she wrote.

Depp has denied hitting Heard or any women and said she was the one who turned violent in their relationship.

Heard, 36, countersued for $153m, saying Depp smeared her when his lawyer called her accusations a "hoax."

The seven-person jury deliberated for more than two hours on Friday (local time) and will resume discussions on Tuesday after the US Memorial Day holiday.

Lawyer Marie Dyhrberg told AM on Monday there were two things both sides needed to do to win their case.

"They're each suing each other in what we call defamation. For either side to win their case against the other, they have to show firstly that the statements that were made were untrue," Dyhrberg told AM co-host Melissa Chan-Green.

"The second thing you have to show is what Americans call actual malice. So in making those statements to at least one other person, whether it's written or said, they've actually intended it. It was intentional and they intended actual malice, so they intended those statements to be defamatory."

At the centre of the legal case is the December 2018 opinion piece by Heard in the Washington Post, in which she made the statement about domestic abuse. 

The article never mentioned Depp by name, but his lawyer told jurors it was clear Heard was referring to him. 

Dyhrberg said Depp's team have to prove those comments by Heard were aimed at him. 

"So what Johnny Depp has to prove is that she meant it was him even though she didn't name him, that the world would see without a doubt she was talking about him," she told AM. 

"So he has to set about or establish just on the balance of probability, that the weight of evidence falls his way that she has made false statements."

Dyhrberg told AM the key to victory for Heard is proving what she said was true.  

"You have to prove or disprove truth because that is a defence. So what Amber Heard's defence to Johnny Depp's suit against her is to say no, what I said was true," Dyhrberg explained.  

"Now, on the other side, Heard has got to show Johnny Depp's lawyer when he said her allegations in the UK were a hoax and false, that Johnny Depp was part-and-parcel of proving that."

Watch the full interview with Marie Dyhrberg above.