New Orleans (AP) — New Orleans prosecutors used to issue fake subpoenas to threaten uncooperative witnesses with jail time, and the district attorney there says they can’t be sued for the deception — but a panel of appeals judges appeared skeptical Wednesday.

Civil liberties advocates have sued District Attorney Leon Cannizzaro and members of his staff over a practice that ended in 2017. The so-called subpoenas had not been approved by a judge, as required, and thus carried no actual threat of jail time.

Lawyers for the prosecutors asked a federal appeals court Wednesday to throw out the lawsuit, arguing that they are immune from suits over practices undertaken as part of their "prosecutorial function."

It was unclear when the three-judge panel of the 5th U.S. Circuit Court of Appeals would rule, but panel members sounded clearly skeptical as W. Raley Alford III, attorney for the prosecutors, made his case.

“Threat of incarceration with no valid premise?” Judge Jennifer Elrod said at one point during arguments. She later drew laughter from some in the audience when she said, “This argument is fascinating.”

“These are pretty serious assertions of authority they did not have,” said Judge Leslie Southwick, who heard arguments with Elrod and Judge Catharina Haynes.

The lawsuit at issue was filed in 2017 by the Civil Rights Corps and the American Civil Liberties Union. Last year, a federal judge agreed that prosecutors had immunity from some of its claims. But U.S. District Judge Jane Triche Milazzo allowed much of the suit to continue, saying some of the claims “shock the conscience.”

Katherine Chamblee-Ryan, an attorney for the Civil Rights Corps, told the panel that by using documents falsely labeled as subpoenas, Cannizzaro's staffers stepped into a role reserved for judges.

The lawsuit was filed amid public complaints that Cannizzaro's office sometimes sought to jail crime victims who would not cooperate with prosecutions. The lawsuit, in addition to targeting phony subpoenas, challenges aspects of the district attorney's office's use of "material witness" warrants that can lead to the jailing of uncooperative witnesses.

The lead plaintiff said she was jailed after declining to pursue charges against a man who shattered her cellphone during a fight. Cannizzaro's office responded to that part of the complaint by saying the woman was legally incarcerated after avoiding legitimate court-issued subpoenas. Cannizzaro also has said the warrants are rarely used to arrest victims of domestic violence or sexual crimes.

Cannizzaro is nearing the end of his second six-year term as district attorney. He has not said whether he will run for re-election this year.