A pair of federal judges went off the legal reservation when they endorsed a new trial for the five New Orleans police officers convicted in the Danziger Bridge killings, government lawyers contend.

The officers were accused of firing on innocent people, killing two of them, a few days after Hurricane Katrina hit the city and then of conspiring to cover up what they had done.

In a 15-page motion filed last week but just unsealed this week, the U.S. Justice Department is asking the full 5th U.S. Circuit Court of Appeals to rehear the arguments in favor of reinstating the convictions.

In the motion, Justice Department attorney Elizabeth Collery slams a 2-1 ruling in August by 5th Circuit Judges Edith Jones and Edith Brown Clement, in which they wholeheartedly backed District Judge Kurt Engelhardt’s stunning 2013 order granting the five officers a new trial.

The request for a new hearing may be the last chance for the government to win reinstatement of the convictions. It’s unclear whether the government would seek to retry the five officers should the 5th Circuit reject it.

In his order, Engelhardt pointed to “grotesque prosecutorial misconduct” by three federal lawyers — Sal Perricone, Jann Mann and Karla Dobinski — who had posted anonymous pro-government comments about the Danziger case beneath nola.com stories.

So egregious were their actions, Engelhardt ruled, that he didn’t need to meet the usual legal standard of finding that the online high jinks had in fact prejudiced the jury.

The two appeals court judges then backed Engelhardt, saying that the nefarious depths of the prosecutors’ online activity may never be fully known.

However, Collery argued in her motion for “en banc” review by the 5th Circuit’s full membership that such doubts don’t justify a new trial for former NOPD Sgts. Arthur “Archie” Kaufman, Kenneth Bowen and Robert Gisevius, and former Officers Robert Faulcon and Anthony Villavaso.

Collery said the former prosecutors’ conduct was “indefensible. But under established law, misconduct, even when it is deplorable, cannot justify setting aside the guilty verdicts rendered after a painstakingly fair six-week trial unless it actually prejudiced the defendants.”

The 2005 bridge shootings occurred as cops responded to a report that a fellow officer was down. When the smoke cleared, 17-year-old James Brissette and 40-year-old Ronald Madison were dead and four others were injured, some grievously.

Engelhardt originally handed sentences of at least 38 years to four of the officers after their 2011 convictions from a 27-count indictment charging them with civil rights, firearms, conspiracy and obstruction counts. Kaufman, who was implicated in the cover-up only, received six years.

After the online posting scandal erupted within then-U.S. Attorney Jim Letten’s office, Engelhardt ordered a special investigation led by a pair of federal prosecutors from outside New Orleans. They turned up evidence that Mann had deceived federal judges by denying any knowledge of the online shenanigans, even though she had herself posted some of the comments.

The investigation also revealed that Dobinski, who was directly involved in the Danziger case, had posted comments during the Danziger trial from Washington, D.C.

Collery, the government attorney seeking the new hearing, contrasted the Danziger case with a different 5th Circuit panel’s ruling in another post-Katrina police shooting: the killing and incineration of Henry Glover in Algiers.

In that case, the officer who admitted burning Glover’s body on the Algiers levee, Officer Gregory McRae, failed to persuade the appeals court that the online scandal had poisoned his conviction.

The appeals panel in that case found no proof of “a connection between the (online) postings in question and the conduct” of the trial “such that we must question our ‘confidence in the jury verdict.’ ”

The conflict between the two rulings warrants a full court hearing in the Danziger appeal, Collery argued.

The government’s plea leans heavily on the dissenting opinion by 5th Circuit Judge Edward Prado, who disagreed with Jones and Clement in the August ruling, writing that the only “newly discovered evidence” that would warrant a new trial was the unmasking of Perricone, Mann and Dobinski.

But, he said, “the defendants advance no credible argument that the newly discovered evidence in this case — the identity of the commenters on nola.com — would likely produce an acquittal.”

Follow John Simerman on Twitter, @johnsimerman.