Aquaman actor Amber Heard has lost a bid for a new trial in her defamation case with ex-husband Johnny Depp after a judge rejected her lawyers’ argument one of the jurors had served improperly.

In June, Heard was ordered to pay Depp $US10.35 million ($15.4 million) in damages when a jury in Fairfax County, Virginia, ruled she had defamed the Pirates of the Caribbean star in a newspaper opinion piece.

Her lawyers had asked the judge to throw out the decision and declare a mistrial, arguing one of the jurors on the case should not have been eligible to serve because his summons was intended for his father, who had the same name and lived at the same address.

Judge Penny Azcarate ruled there was “no evidence of fraud or wrongdoing” by the juror and that the verdict should stand.

She also noted both sides had questioned and accepted all jurors at the start of the trial.

“Due process was guaranteed and provided to all parties in this litigation,” Judge Azcarate wrote.

Depp, 59, had sued Heard and argued she defamed him when she called herself “a public figure representing domestic abuse” in an opinion piece published in The Washington Post.

Depp denied hitting Heard, 36, and said she was the one who turned violent in their relationship.

Heard countersued, saying Depp smeared her when his lawyer called her accusations a “hoax”.

The jury awarded Heard $US2 million ($3 million) in damages on one of her counterclaims. Heard said she struck Depp only in defence of herself or her sister.

-AAP