PHILADELPHIA (AP) — Of the nearly 3,500 people exonerated of serious crimes in the U.S. since 1989, more than half had their cases marred by alleged misconduct by police or prosecutors, according to a national database.

But experts say it’s rare for anyone to be held accountable for the harm — for the coerced confessions, hidden evidence, false testimony and other dubious work that contributes to flawed convictions.

The pending perjury trial of three retired Philadelphia police detectives could prove an exception, if they themselves are not cleared by alleged mistakes by District Attorney Larry Krasner’s office. Former detectives Martin Devlin, Manuel Santiago and Frank Jastrzembski have asked a judge to dismiss the case. The judge plans to rule by April.

An unusual confluence of factors allowed Krasner to charge the three in the case of exoneree Anthony Wright, who in 1993 was convicted of the 1991 rape and murder of an elderly widow. Chiefly, the detectives had testified at his retrial in 2016, reopening a five-year window to file perjury charges.

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Wright, who left school in seventh grade, was arrested at age 20. He spent two decades in prison before DNA testing seemingly cleared him of the crime. Nonetheless, Krasner’s predecessor chose to retry him, and called the detectives out of retirement.

Besides the DNA, the other key piece of evidence in the retrial was Wright’s confession. His lawyers argued that it was coerced. The detectives denied it.

In a dramatic courtroom showdown, lawyer Sam Silver, representing Wright, asked Devlin to write down the nine-page confession in real time, as Devlin said he had done “word for word” in 1991. The once-famed detective — who helped nab a New Jersey rabbi in his wife’s murder-for-hire — jotted down only six words before giving up.

Wright told jurors that police had made him sign the confession without reading it. They deliberated just a few minutes before acquitting him, and the forewoman hugged Wright before sending him home.

That trial testimony was still fair game when Krasner, a civil rights lawyer focused on criminal justice reform, took office in 2018. He has championed 40 exonerations to date, and pursued a small number of police perjury cases, often over active investigations.

He charged the Wright detectives in 2021, days before the five-year deadline expired.

Santiago and Devlin are accused of lying about the confession. Santiago and Jastrzembski are accused of lying when they testified they didn’t know about the DNA problem. Jastrzembski is accused of lying about finding the victim’s clothes in Wright’s bedroom. They are all now in their mid- to late 70s and maintain their innocence.

Experts in the exoneration community can cite just a handful of similar efforts to charge police or prosecutors in their cases. Meanwhile, public agencies across the country have paid out $4 billion to compensate people for the nine years, on average, they wrongly spent in prison, according to The National Registry of Exonerations.

“We’re willing to accept remediation of the harm, but we’re not prepared to accept accountability of the culpable,” said Alan J. Tauber, a Philadelphia defense lawyer who has helped free three men from prison after wrongful convictions.

There’s also a high legal bar for proving perjury. Marissa Bluestine, the former director of the Pennsylvania Innocence Project, said testimony needs to be intentionally deceitful, not just mistakenly so, to convict someone of perjury.

“It’s an incredibly hard burden to meet,” said Bluestine, now assistant director of the Quattrone Center for the Fair Administration of Justice at the University of Pennsylvania.

Last year, a mistake by prosecutors sank a police perjury case in Manhattan, when a judge halted the trial over their failure to turn over evidence to the defense. And an FBI racketeering case against Philadelphia’s narcotics unit, which alleged members routinely robbed drug dealers and lied about it, ended with a 2015 jury acquittal. The only officer sent to prison had testified against his colleagues.

Wright, 53, settled a lawsuit against the city for nearly $10 million. In all, he spent 25 years in prison.

“That case was remarkable. There was a DNA exclusion, and they said they were going to try it anyway,” said Maurice Possley, a senior researcher at the exonerations registry.

The group’s data show the disproportionate harm that botched prosecutions cause Black defendants like Wright. Black people make up 13.6% of the U.S. population but 54% of the 3,433 exonerations studied. (The total is now 3,464.) And they lose more years of their lives — 10.1 years vs. 7.7 years for white people and 8.3 years for Hispanic people — before being cleared.

The detectives’ trial was set to start in January, but is on hold while a judge reviews defense objections to grand jury testimony that suggested Devlin had a history of coercing confessions and that a jury in another case had found him “evil.” Common Pleas Judge Lucretia Clemons agreed the jury note was “inflammatory,” according to The Philadelphia Inquirer. It’s unclear if that’s enough to taint the case.

Defense lawyer Brian McMonagle accused Krasner’s office of trying to “smear” the detectives’ reputations. He declined to comment on their behalf outside the courtroom.

Wright has been outspoken since leaving prison, but declined an interview while the case is in limbo. However, he once told The Inquirer that it would “mean everything to me if those guys individually can be held accountable for what they did to me.”

As part of Wright’s lawsuit, the detectives had to give videotaped depositions. At one point, his lawyers ask Santiago which is worse: to put an innocent man in prison or let a guilty man go free. The retired sleuth said each would be a “terrible thing,” but settled on the latter.

“When the guilty man walks away, only those responsible for his walking away … have to live with it. So yeah, it’s worse,” Santiago said.

Tauber, who served as the city’s top public defender, said the statement shows “the values that our system is founded on have been turned on their head.”

“And not only turned on their head, but adopted and internalized by the people largely responsible for investigating and administering justice.”