Depp, 58, alleges Heard, 35, defamed him when she penned a December 2018 opinion piece in the Washington Post about being a survivor of domestic abuse. He filed a $50 million lawsuit against Heard in 2018.
The article never mentioned Depp by name, but Depp lawyer Benjamin Chew told jurors it was clear Heard was referencing the Hollywood leading man.
Attorneys for Heard, also an actor, have argued she told the truth and that her opinion was protected as free speech under the U.S. Constitution's First Amendment. In opening arguments, Heard's attorneys said Depp physically and sexually assaulted her while abusing drugs and alcohol.
A state court judge in Fairfax County, Virginia, is overseeing the trial, which is in its second week and is expected to last for six weeks.
On Tuesday, Depp's lawyers asked him about his movie career and his early interactions with Heard on the set of 2011 film "The Rum Diary." Depp described her at that time as sweet, intelligent and funny.
The actor also detailed his parents' tumultuous relationship.
Depp said his parents frequently argued and his mother physically abused her children. Depp said his father never fought physically with his mother but punched a wall as many as three times, once breaking his hand. His father left the family when Depp was 15, the actor said.
By that time, Depp had "done all the drugs I was aware of," he said. He said he became addicted to opiates after he was injured on the set of the fourth "Pirates" film but recovered from that dependency.
Depp said Heard "grossly embellished" his substance use. "A lot of it is just plainly false," he said. "I think it was an easy target for her to hit."
Heard watched the testimony with little expression while Depp spoke, occasionally tilting her head or jotting notes.
Less than two years ago, Depp lost a libel case against The Sun, a British tabloid that labeled him a "wife beater." A London High Court judge ruled he had repeatedly assaulted Heard and put her in fear for her life.
In the U.S. case, Depp and Heard both submitted long lists of potential witnesses they may call, including Heard's ex-boyfriend and Tesla Chief Executive Elon Musk and actor James Franco.
Depp's lawyers have said they filed the case in Fairfax County, outside the District of Columbia, because the Washington Post is printed at a facility there. The Washington Post is not a defendant in the case.
The United States is a difficult forum for libel plaintiffs, especially public figures like Depp, who must prove by clear and convincing evidence that Heard knowingly made false claims.
Heard, known for roles in "Aquaman" and "Justice League," has brought her own libel claim against Depp, saying he smeared her by calling her a liar.
Heard's counterclaim, seeking $100 million in damages, will be decided as part of the trial.
