The actress lost her original case against ex-husband Johnny Depp earlier this year.
In June, Heard was ordered to pay Depp $10.35 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 attorneys at the time asked the judge in the case to throw out the decision and declare a mistrial, arguing that 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.
High-profile attorneys David L Axelrod and Jay Ward Brown will now take over from former lead Elaine Charlson Bredehoft, who will step down from the case.
Bredehoft said she would continue to support Heard in her case.
Said Bredehoft, “This is the perfect time to pass the baton. I have pledged to Amber and her appellate team my complete cooperation and assistance as they move forward on a path towards success.”
Heard’s team said: “When it comes to protecting the fundamental right of Freedom of Speech, we look at the jury’s decision – to paraphrase a famous quote – not ‘as the beginning of the end, but merely the end of the beginning’.
Attorneys Axelrod and Brown successfully defended The New York Times against Sarah Palin’s defamation lawsuit earlier this year.