Rogers LaCaze, who was shipped to Louisiana’s death row 20 years ago along with former New Orleans Police Department Officer Antoinette Frank for the most infamous New Orleans massacre in a generation, deserves a new trial on first-degree murder charges, a judge ruled Thursday.

In a blockbuster 128-page decision, retired Judge Michael Kirby found “a structural error” in LaCaze’s trial on three counts of first-degree murder — namely, that one of the jurors, David Settle, was a commissioned law enforcement officer for the State Police at a time when they were legally barred from jury service and that he hid that fact from the court.

Kirby, a retired Plaquemines Parish and 4th Circuit Court of Appeal judge, found little merit to the litany of other claims raised by LaCaze’s attorneys, who have argued for years that his case was botched by prosecutors, police, the judge at his trial and his own, now-deceased trial attorney.

LaCaze’s attorneys with the New Orleans-based Justice Center claimed his conviction and death sentence were the result of an unconstitutionally slipshod defense, biased jurors and the suppression of key evidence by prosecutors with former District Attorney Harry Connick’s office.

In his ruling, Kirby said he found the evidence of LaCaze’s guilt “overwhelming” but that the juror question alone warranted a new trial.

“For 20 years, Rogers LaCaze has been asking for what every defendant is entitled to: a competent attorney and a fair trial in front of an impartial jury,” said LaCaze’s attorney, Blythe Taplin. “While we disagree with some of the findings in the court’s order, this is the only just result. Mr. LaCaze looks forward to his day in court.”

LaCaze’s attorneys also argued that the death sentence for LaCaze, now 38, was unconstitutional because he is mentally disabled. Kirby said they could take up that claim at the next trial.

The judge remanded LaCaze without bail, meaning he’ll remain behind bars while District Attorney Leon Cannizzaro’s office makes its next move.

“We are reviewing it right now. We do intend to appeal it,” said Christopher Bowman, a spokesman for Cannizzaro’s office.

The decision came almost exactly 20 years after a jury found LaCaze guilty of three counts of first-degree murder in the killing of Frank’s partner, Officer Ronnie Williams II, 25, and siblings Cuong Vu, 17, and Ha Vu, 24, inside the Kim Anh restaurant in New Orleans East.

The March 4, 1995, slayings marked a low point in image and morale for a Police Department that was beset by corruption charges and an explosion of deadly street violence, with the city’s murder rate about double what it is today. It peaked in 1994 at 421 murders.

Inside Kim Anh, there were police officers on both ends of the fatal bullets.

Williams had worked a security detail at the restaurant with Frank, who had dined there with LaCaze on the evening of the murders. LaCaze and Frank were convicted in separate trials within months of the bloody melee, and they remain the most recent Louisiana death-row inhabitants from Orleans Parish.

Prosecutors theorized that the 18-year-old LaCaze and the 23-year-old rookie cop were lovers and had come and gone from the Kim Anh restaurant together multiple times on the night of the killings.

Frank led Ha and Cuong Vu’s sister, Chau, to the back of the restaurant when the gunshot that ended Williams’ life rang out at the front of the business, according to testimony at LaCaze’s trial.

Frank then ran toward the front of the restaurant. As she and LaCaze robbed the restaurant, Ha Vu and Cuong Vu also were killed, according to testimony.

Chau Vu, another of her brothers, Quoc Vu, and a restaurant worker hid in a walk-in cooler.

Frank then joined other officers who responded to the 911 call from the restaurant massacre, acting as if she was there to help investigate the killings, according to testimony.

Frank was soon arrested, identified by those in the cooler. So was LaCaze, who police said used Williams’ credit card to buy gasoline on the West Bank following the killings.

LaCaze has always denied being at the restaurant at the time of the killings, saying he was at a pool hall when the shootings occurred.

Kirby filed his ruling more than two years after the first in a series of court hearings began on an appeal based in part on an extraordinary assertion by LaCaze’s attorneys.

They argued that evidence the 1995 jury never heard suggested it was Frank’s brother, Adam Frank, who was her violent accomplice, not LaCaze.

At his trial, LaCaze was portrayed as the one who shot each of the victims. But his attorneys claim Connick’s office withheld a key witness statement pointing to Antoinette Frank as the shooter.

The 15 months Kirby took mulling the case before his ruling Thursday were in stark contrast to the less than 90 days it took to convict LaCaze after his indictment.

The same jury sentenced LaCaze to death the following day. Two months later, another jury delivered the same fate to Antoinette Frank.

Neither Frank nor LaCaze was found with the gun or the $10,000 in cash missing from the restaurant.

LaCaze’s attorneys presented evidence that police once considered Adam Frank as a suspect in the bloody rampage. Adam Frank moved from New Orleans to northeastern Louisiana after the killings, and people who knew him there by an alias, Keith Jackson, have signed affidavits saying he claimed to have been an NOPD officer with a uniform, police ID and scanner.

Adam Frank was booked in Rayville in 1998 after a confidential informant said he heard Frank bragging about killing a New Orleans cop, according to LaCaze’s attorneys. Police searched his car and found handguns, a rifle, a dagger, $1,300 in cash and money orders made out to his imprisoned sister.

It took four officers to subdue him, and he later escaped custody after putting an officer in a headlock and causing a police cruiser to crash. Police captured him a month later, finding him with a 9 mm Beretta that tests would show matched the firearm — possibly the murder weapon — that Antoinette Frank had reported stolen a few weeks earlier.

Adam Frank later was given a 65-year prison sentence and grew close with a man named Darran Reppond, who took center stage in LaCaze’s appeal. Reppond claimed Adam Frank gloated about shooting an officer at a New Orleans restaurant.

Reppond testified that Adam Frank told of a massacre, saying an officer “shook him and his sister down over some money,” so he and his sister “ran him down and shot him in the head.”

Frank stands a foot taller than LaCaze, a fact prosecutors cited as clear evidence that witnesses would not have been likely to confuse them.

In his ruling, Kirby said he was “inclined to believe Mr. Frank,” who denied telling Reppond anything. In Reppond’s telling, the judge noted, Adam Frank never talked about the two other victims.

“If Mr. Frank was making a boast to impress his jail mates, then it would seem he would have taken the macabre credit for all of the killings,” Kirby wrote.

“Quite simply I find the evidence of Mr. LaCaze’s guilt overwhelming: He was seen in the company of Ms. Frank at Wal-Mart less than 12 hours before this execrable massacre attempting to purchase cheap ammunition. Two of the survivors positively identified him rummaging through the kitchen after the gunfire,” Kirby wrote in his ruling. “They had each seen him twice earlier that evening and were well acquainted with Adam Frank so as not to mistake Mr. LaCaze for him.”

LaCaze’s attorney at the time, Willie Turk, is dead, which Kirby acknowledged complicated his decision on what Turk knew or didn’t know and what in his defense of LaCaze was lapse and what was legal strategy.

Kirby dismissed numerous claims by LaCaze’s attorneys.

Among them:

That LaCaze’s case was marred by Turk’s failure to properly vet the prospective jurors for their knowledge of the high-profile case.

That Connick’s office withheld witness statements that would have been favorable to LaCaze’s defense and that one witness identified LaCaze through suggestive manipulation by police.

That LaCaze couldn’t get a fair shake before Criminal District Court Judge Frank Marullo, who presided over both trials while refusing to cooperate in an investigation of an earlier order from Marullo granting Antoinette Frank a 9mm Beretta pistol from the NOPD property room. The three victims were killed by a 9mm handgun that was not recovered.

Kirby said it was clear that the target of that investigation was not Marullo but Officer David Talley, the former head of the property and evidence room, where Frank had worked as a recruit.

Marullo in 2013 testified that the order for the weapon, with his signature on it, was a “phony document.” LaCaze’s attorneys argued that Marullo should have recused himself from the case.

“Simply put, it is highly improbable that Judge Marullo’s reluctance to become involved in an internal NOPD investigation constituted an awareness of some illegality or wrongdoing that he had to cover up,” Kirby wrote, dismissing a “sinister” suggestion that Marullo was hiding something.

Kirby acknowledged that prosecutors with Connick’s office suppressed information that Frank had obtained a 9mm weapon from Talley, but he said he didn’t think it would have been enough to sway the jury’s mind against convicting LaCaze in the three murders.

A claim that Turk failed to hire a crime scene expert and failed to challenge the prosecution’s theory of the case was “a seductive argument,” but Kirby found that Turk “did the best he could with the available evidence.”

The defense attorney’s failure to investigate or present mitigating evidence on LaCaze’s behalf in the penalty phase was moot, Kirby ruled, since he’d already found that the jury issue warranted a new trial.

Still, “Mr. Turk’s austere presentation at the penalty phase did not come close to the competent, effective representation that Mr. LaCaze was entitled to,” Kirby wrote, anticipating an appeal of his ruling.

Kirby, however, sided with LaCaze’s attorneys in finding that Settle — the man improperly seated on the jury — failed to reveal during questioning that he had worked previously as a railroad policeman and was working as a public safety officer for the State Police.

“There is simply no excuse for him not mentioning his employment status,” Kirby wrote. “Although I find the evidence of Mr. LaCaze’s actual guilt compelling, he is entitled to a new trial because his trial was afflicted with a structural defect, i.e. the violation of a constitutional right so basic to a fair trial it cannot be treated as a harmless error.”

Staff writer Ramon Antonio Vargas contributed to this story. Follow John Simerman on Twitter, @johnsimerman.