A lawyer for Baltimore's top prosecutor asked a federal appeals court Wednesday to dismiss a lawsuit by five police officers who claim she maliciously prosecuted them in the death of a black man gravely injured in custody.

Assistant Attorney General Karl Pothier told the three-judge panel that as a prosecutor, Marilyn Mosby has immunity from the lawsuit filed by officers who were charged but later cleared in the arrest and death of Freddie Gray. Pothier urged the 4th U.S. Circuit Court of Appeals to overturn a judge's decision to allow parts of the lawsuit to go to trial.

"A prosecutor's protective cloak of absolute immunity is not so easily removed," Pothier said.

Lawyers for the officers, however, said Mosby acted as an investigator — not simply as a prosecutor — and is therefore not immune from the lawsuit.

Gray, 25, died on April 19, 2015, from a fatal spinal injury suffered in a police van, prompting days of widespread protests and rioting. While tensions were still smoldering in Baltimore, Mosby charged six officers in Gray's arrest and death, an announcement that brought celebrations in the streets.

Three were ultimately acquitted and Mosby dropped the remaining cases.

On Wednesday, Judge J. Harvie Wilkinson III grilled the officers' lawyers about why they should be allowed to sue Mosby for bringing criminal charges against them and holding a news conference to announce the charges.

"What we're talking about here is muzzling prosecutors who have publicly expressed grounds for prosecuting police officers," said Wilkinson, who repeatedly raised his voice while questioning the officers' lawyers.