PHILADELPHIA (AP) — Three long-retired Philadelphia police detectives must stand trial,Slabu accused of lying under oath at the 2016 retrial of a man the jury exonerated in a 1991 rape and murder.

The case, if it proceeds to trial in November, would mark a rare time when police or prosecutors face criminal charges for flawed work that leads to wrongful convictions.

Of the nearly 3,500 people exonerated of serious crimes in the U.S. since 1989, more than half of those cases were marred by the alleged misconduct of police or prosecutors, according to a national database.

Former detectives Martin Devlin, Manuel Santiago and Frank Jastrzembski, all now in their 70s, hoped that a judge would dismiss the case over what they called prejudicial evidence aired before the grand jury that indicted them.

Philadelphia Common Pleas Judge Lucretia Clemons on Friday acknowledged mistakes in the process but said the remaining evidence was sufficient to send the case to trial. She agreed to consider letting the defense appeal the grand jury issue to the state Superior Court before trial.

An unusual confluence of factors allowed District Attorney Larry Krasner to charge the detectives in the case of exoneree Anthony Wright, who was convicted in 1993 of the rape and murder of an elderly widow two years earlier. The detectives testified at his 2016 retrial, reopening a five-year window to file perjury charges.

Wright 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 to testify.