As a federal court hearing approached this past June, four supervisors under Philadelphia District Attorney Larry Krasner took a hard look at a murder-exoneration case the office had backed since 2022.

They "started to panic," a federal judge later wrote.

A filing from Krasner's office endorsing a new trial for Dennis Johnson, who is serving a life sentence, contained major factual errors. The prosecutor who wrote it resigned, and two weeks before the hearing the office abruptly withdrew its support for a new trial. That prompted the judge to hold hearings where key players in Krasner's office testified about what went wrong.

Now, the scandal threatens to engulf Krasner, one of the nation's most prominent prosecutors, and is rippling through Philadelphia.

On Sept. 15, U.S. District Judge Paul Diamond, an appointee of President George W. Bush, issued an extraordinary 40-page opinion finding that Krasner embraced a plan to scapegoat a junior prosecutor for the flawed filing and warned high-ranking deputies of "consequences" if they did what they saw as their professional duty.

Diamond referred the third-term Democrat to the Justice Department for investigation, concluding he may have engaged in a coverup that obstructed justice and amounted to a criminal conspiracy.

Krasner said he "respectfully and vigorously" disagrees with the findings in the opinion, which also disqualified him from further involvement in the exoneration case. "I look forward to appealing to the higher court as soon as the law allows," he stated.

Krasner was one of the first progressive prosecutors elected nationwide and is among the last still in office after voters ousted others amid the postpandemic crime surge. He has made overturning wrongful convictions a priority from the start. One of those cases has now thrown his office into disarray.

Krasner, 65 years old, is a blunt-spoken, former civil-rights attorney first elected in 2017 with the financial backing of billionaire investor George Soros. Last year he won his third four-year term with 76% of the vote. Like many progressive prosecutors, he has clashed with the right, but he has also tangled with establishment Democratic power brokers in Philadelphia, and there has been speculation he might challenge Mayor Cherelle Parker, a centrist Democrat, next year.

The current crisis stems from Johnson's conviction in 2009 for the fatal shooting of Kenyatta Smith at a North Philadelphia convenience store.

Johnson has maintained his innocence and lawyers from the Pennsylvania Innocence Project, which seeks to free the wrongfully convicted, have worked with his public defenders to clear him.

In 2022, Krasner's office, which says it has supported around 60 exonerations, joined the effort to get Johnson a new trial.

'Good enough for me'

According to Judge Diamond's opinion, the turmoil began when Matthew Stiegler, a district attorney's office supervisor, assigned the Johnson case to Jaclyn Mason, an experienced lawyer who had been a prosecutor for just four months. Stiegler didn't tell Mason to review the case independently, allegedly saying, "If it's good enough for the Innocence Project, it's good enough for me."

Stiegler told Diamond he thought Mason would do a full investigation, a claim the judge said he didn't find credible. Stiegler didn't respond to a request for comment.

In May 2022, Johnson's lawyers said they had new evidence to back up his innocence. They said that one of the two witnesses who testified he was the shooter had recanted and that a third man-who a detective had told jurors also identified Johnson-claimed he hadn't told the detective that, Diamond wrote, citing court affidavits.

In a court filing that fall, Mason wrote on behalf of the district attorney's office that Johnson deserved a new trial because his defense lawyer hadn't contested the detective's hearsay testimony. A federal magistrate judge subsequently recommended overturning the conviction due to ineffective defense counsel.

However, after Diamond scheduled the hearing to review the evidence, the four district attorney's office supervisors, not including Stiegler, began reviewing the case.

Two of the supervisors realized Mason's filing contained major errors, such as contradicting the trial record by asserting one witness never visually identified Johnson as the shooter.

'We need to protect the office'

Mason, worried she would be solely blamed, resigned on June 2 and claimed Stiegler "used me to further his personal agenda...regardless of the merits," Diamond wrote.

The office fractured.

Stiegler soon pitched one of the supervisors on telling Diamond the office had found mistakes in Mason's other cases, so the judge would "view this as one rogue" prosecutor.

Later that day, the four supervisors met with Krasner to seek approval to withdraw the 2022 filing and ask him to refer the case to the state attorney general's office because of conflicts within the district attorney's office. Krasner edited their motion to lessen Stiegler's apparent involvement, Diamond wrote, and the four filed it with the court.

At the same meeting, Diamond wrote, Krasner told the four that Stiegler "gave me this really good idea. I think that we should go through Ms. Mason's cases, find mistakes that she made in other cases, say that this was a pattern by her, and then file something with the Court saying that."

The four rejected the idea, Diamond wrote. Krasner, meanwhile, resisted bringing in Pennsylvania's Republican Attorney General Dave Sunday. Krasner repeatedly ranted, calling the attorney general's team "Nazis" and spoke of the need to defend his own turf, saying, "We need to protect the office," according to the opinion.

Krasner said "protect the office" meant "preventing outside bias and outside conflict from unjustly impacting the office's justice work," according to a court filing in his defense.

An outside ethics expert Krasner consulted said neither he nor the district attorney's office needed to be removed from the case, though Diamond said the expert "ignored critical facts." A former Missouri prosecutor Krasner hired to review the case said in an affidavit that Johnson's innocence claim should be rejected.

By late June, several Krasner subordinates drafted a letter handing off the case to the attorney general's office. Krasner reacted angrily, the judge wrote, warning that anyone who alerted the court to the discord would face "consequences, whatever they may be," which some lawyers understood to mean potential firing.

"Mr. Krasner's threat thus could amount to obstruction of justice," Diamond wrote. He added: "I have also found that Mr. Krasner and Stiegler worked together to try to convince the Four [supervisors] to urge the Court to accept a false narrative. This might amount to criminal conspiracy."

"I have thus reluctantly concluded that Philadelphia's highest law-enforcement official and one of his top assistants may have violated the law," wrote Diamond.

Legal observers say the situation might be unprecedented. "I can't think of an instance when this has happened before, where a federal judge has referred a sitting district attorney for criminal investigation," said Temple University law professor Lauren Ouziel, a former federal prosecutor.

The scandal has been front-page news in the city; the Philadelphia Inquirer's editorial board called it an "untenable situation."

Casting the referral as political, Krasner invoked various stalled or failed Trump administration prosecutions. "Ask Letitia James, James Comey, the 'sandwich man' or the guy who took peeling paint from the reflecting pool what they have to say about accusations," he said in a statement to the Inquirer.

Krasner "should absolutely resign," said state Rep. Martina White, the only Philadelphia Republican in the Pennsylvania House of Representatives. "It's an embarrassment to our city."

But Krasner ally Sergio Cea, political director at advocacy group Reclaim Philadelphia, portrayed the judge's move as a GOP effort "to take down this progressive boogeyman."

The Innocence Project and other lawyers representing Johnson said their focus remains "on Dennis, whose innocence we firmly believe in, and for whom we will continue to fight."