The finger injury, which occurred in a March 2015 fight in Australia between Depp and Heard, has been one of several key points of dispute in the lawsuit.
Depp says he was injured when Heard threw a vodka bottle at him.
Heard has said she never saw specifically how it happened, but claimed it occurred on a night when an enraged Depp sexually assaulted her with a liquor bottle.
Depp is suing Heard for libel in Fairfax County Circuit Court over a December 2018 article she wrote in The Washington Post describing herself as "a public figure representing domestic abuse".
His lawyers say he was defamed by the article even though it never mentioned his name.
Depp has denied he ever struck Heard, and says she was the abuser in the relationship.
Heard has testified about more than a dozen separate instances of physical abuse she says she suffered at Depp's hands.
In testimony on Monday, surgeon Richard Moore testified about the severed finger as jurors saw gruesome photos of the injury.
He said Depp described his palm as being down on a bar when it was struck by the bottle.
Moore, who did not treat Depp, testified Depp's description is unlikely, in large part because his fingernail remained intact.
Moore said the fingernail was exposed, as Depp described the placement of his hand, and would have been damaged. Moore also said there would have been other cuts on his hand from the glass that shattered on impact.
While Depp told the jury Heard severed the finger by throwing a vodka bottle, at the time of the accident he told people and sent text messages saying he had done it to himself.
At one point he said the finger had been pinched between solid accordion doors.
Depp now says he lied to protect Heard. Moore testified getting the finger pinched in accordion doors would be consistent with the injury.
The trial is now in its sixth week. Monday's testimony was relatively mundane in a trial that has provided an ugly glimpse into the couple's toxic relationship.
There had been an expectation Heard's lawyers were going to call Depp to the stand on Monday, but that did not occur.
Heard's lawyer Elaine Bredehoft said at the end of the day they are still discussing whether to call him.
Jurors have already heard extensively from Depp and Heard - each was on the stand for four days.
Also on Monday, a psychiatrist testified Depp's behaviour fits the pattern of a person whose drug and alcohol abuse contributes to domestic violence.
Depp's lawyer Wayne Dennison questioned the ethics and credibility of the psychiatrist's opinions, given he never conducted an examination of the Pirates of the Caribbean actor.
Dennison also extensively questioned another Heard witness, entertainment expert Kathryn Arnold, about her assertion Heard lost out on a potential $US40 million to $50 million when another Depp lawyer called Heard's claims of abuse a "hoax".
Heard has filed a counterclaim against Depp based on those statements.
Arnold said she measured Heard's career against "comparable" stars like Gal Gadot, Jason Momoa and Zendaya to show where Heard's career would have gone if Depp attorney Adam Waldman had not defamed her.
Dennison, in his questioning, scoffed at the notion that Heard was in the same league as those stars.
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