The 57-year-old actor is suing the British tabloid's publisher News Group Newspapers (NGN), and its executive editor Dan Wootton, over a 2018 article which labelled him a "wife beater."
According to London's Evening Standard newspaper, on the third day of the trial on Thursday (09Jul20), Depp admitted he had a "collision" with Heard, 34, after she allegedly advanced on him "flailing and punching" during an argument in December 2015.
Britain's High Court heard a recording of a conversation between the couple shortly after the altercation, in which Depp appeared to say he only headbutted her in the "f**king forehead" - which wouldn't "break a nose."
The "Pirates of the Caribbean" star defended his actions while being cross-examined by The Sun's lawyer Sasha Wass, saying the incident was accidental after she attacked him, and that injuries shown in photographs submitted as evidence were not consistent with what happened.
"This injury that she would've suffered is not consistent with the photographs that she has given to the court," he claimed. "She was swinging wildly at me, and I ... from behind, as I was walking away from the argument to my office, she was hitting me in the neck, ear, back, everything.
"I turned to cover my head and she was swinging quite wildly so the only thing I could do in that situation was either to run or to try to get hold of her, to get my arms around her to stop her flailing and punching me, so I did so, as I did so it seems there was a collision."
Depp demonstrated to the court with his arms how he claims he took hold of his ex and indicated she was "kicking and moving" so there was "very close contact."
He added, "That is the only collision and the only potential injury that Ms Heard could have had, there is no way I did as she said and broke her nose."
In addition to photographs of the "Aquaman" star's alleged injury, the court was also shown pictures of Depp with "scratches and swelling around my face" allegedly inflicted by his ex.
In response to Wass's suggestion he was violent towards his ex-wife, whom he was married to from 2015 to 2017, the actor denied this, saying he would "run away" from fights and was "called a coward and a pussy for trying to avoid an escalation."
The incident is one of 14 times Heard alleges her ex-husband was violent towards her, which The Sun's lawyers are using to defend their case. He denies all the allegations.