On April 19, 1999, Michael Banks and Gordon Cooney traveled from Philadelphia to Louisiana’s death row at the State Penitentiary at Angola to meet with their client, John Thompson. Banks and Cooney had represented Thompson since 1988, and his appeal for capital murder was rapidly reaching an inexorable conclusion. Despite the lawyers’ best efforts, they had failed. The U.S. Supreme Court had rejected their final petition. Thompson’s eighth—and final—death warrant had been signed by the judge. John Thompson was scheduled to be executed by lethal injection on May 20, 1999.

Banks and Cooney had a brief and emotionally wrenching meeting with Thompson, made worse by the fact that Thompson was more concerned about them than he was about himself. Exhausted and demoralized, they began the long drive back to New Orleans, where they would have to tell Thompson’s mother that they had been unable to save her son’s life. During the drive, Cooney checked his voice mail. What he found was a message from a private investigator with surprising new evidence in the case—the first pull on a thread that would take John Thompson off death row, then out of prison entirely, and this week to the United States Supreme Court.

Stories of wrongful imprisonment are so frequent these days that we barely notice them. A man was released today after [two, 10, 27 years] in prison for a [murder, rape, robbery] he didn’t commit. Newly unearthed evidence shows [he, she, they] couldn’t have committed the crime. The descriptions drone on as our minds wander elsewhere. Another DNA case, we think, with the defense lawyers reaching back, CSI-style, for a piece of hair or a new test of decade-old semen.

In fact, it’s rarely that easy. Even today, DNA evidence is only available in about 10 percent of criminal cases. Thousands of people each year are convicted of crimes on the basis of eyewitness and circumstantial testimony, without any scientific evidence linking them to the crime. And in the few cases in which DNA evidence is available, challenges of collection, maintenance, and storage often create problems. So we know that lots of convictions are based on evidence with holes—and that the DNA evidence that is used to rebut it can be hard to come by. So as a practical matter, how do lawyers representing convicts on appeal find the evidence suggesting their clients are innocent? That question is the backdrop to next week’s Supreme Court battle.

In John Thompson’s case, there was no physical evidence linking him to the crime—the brutal robbery and murder of an unarmed New Orleans hotel executive in early December 1984. The shooting was outdoors, and no blood, fabric, or hair samples were collected at the scene. Ballistics confirmed that police had found the murder weapon, but Thompson’s fingerprints weren’t on it. Instead, Thompson’s conviction was based entirely on the testimony of four witnesses. Kevin Freeman, also arrested for the murder, testified (in exchange for a plea bargain) that he had seen Thompson pull the trigger. Two other men (who received cash rewards for their testimony) stated that they had heard Thompson confess to the killing, and another man (whose rape charge had been dropped by prosecutors two days before) said that Thompson had sold him the gun.

The murder victim was the son of a well-connected New Orleans businessman. Solving the case was a priority for the district attorney, Harry Connick Sr., a dapper and charming politician with a deep love for the old standards, which he sang at a weekly gig in a New Orleans nightclub. Connick also was known for some aggressive theories of criminal law, including his resistance to “open file discovery,” the theory that prosecutors should simply provide all evidence in their files to defense lawyers. Connick sent a message of the importance of the businessman’s murder by appointing his third-in-command, Assistant DA Eric Dubelier, to it and adding his most experienced homicide prosecutor, Assistant DA Jim Williams.

After a six-week investigation, Thompson and Freeman were arrested on the basis of the accounts of Freeman and the other witnesses and the murder weapon. Freeman quickly rolled on Thompson in exchange for a plea, creating a neat bundle of evidence for the prosecutors. They charged Thompson with murder one, but they wanted more. Connick had been elected on a commitment to seek the death penalty for all first-degree murder cases, and Louisiana required an “aggravating factor” to be added to the murder before a jury could sentence Thompson to death. Thompson, who had no violent priors, did not readily provide one.

The prosecutors’ problem was quickly solved. The day after Thompson’s arrest, his picture ran on the front page of the New Orleans Times-Picayune. Stewart Lagarde, a father of three in the New Orleans suburbs, called police and said that his children could positively ID Thompson as the man who had carjacked them outside the Superdome in late December. Although the carjacking was committed three weeks after the murder, Dubelier and Williams tried the carjacking first.

As in the murder, police had a gun, but no prints. Even so, three white teenagers identifying Thompson in open court overwhelmed Thompson’s alibi (he claimed he was at work). The jury convicted Thompson of armed robbery. One month later, Dubelier and Williams successfully convicted Thompson of murder, and using the carjacking as an aggravating factor, convinced the jury to sentence Thompson to death.

As lawyers representing Thompson’s appeal, Banks and Cooney were required to confine themselves to legal problems with the trial. The facts had been established by the juries’ verdicts. It was now fact that Thompson had committed the murder, and fact that he had carjacked the teenagers. As a result, Banks and Cooney largely focused on the procedural aspects of both trials. They noted, however, that in the carjacking there had been a scuffle, with blood spilled. The police had collected two samples of the blood, from a pair of pants and a tennis shoe of the oldest Lagarde child, but the samples were not used at trial. Still, to be thorough, Banks and Cooney sent the DA’s office a written request in 1989 asking for those samples and any related blood tests. The DA’s office denied that any such information existed, and Thompson’s appeal moved forward.

By 1999, the 5th Circuit Court of Appeals had rejected the lawyers’ best arguments on Thompson’s behalf, and the likelihood that the U.S. Supreme Court would act was virtually zero. Desperate, Banks and Cooney hired a private investigator named Elisa Abolafiya to search for new evidence. It was the definition of a long shot, but with a man’s life in the balance, it was worth a few thousand bucks.

Abolafiya typically worked as a “mitigation investigator,” someone who joins a case post-conviction and digs deep into the inmate’s background to see if there is information that can be used to reduce his sentence—was the inmate beaten as a child, or was his IQ sufficiently low that he could not have understood the ramifications of his actions. In this instance, however, she was working as a “fact investigator,” delving into the facts of his murder and carjacking cases to find what the police might have missed, looking for anything not previously known to defense lawyers that could reopen the case.

Abolafiya was one of those “only in New Orleans” people: a private investigator cum local radio personality with a fondness for long, flowing robes and dozens of bangles and beads. She hosted a late-night salsa and calypso radio program with a side gig as a DJ at parties. She quickly ruled out going to the DA’s office; there was no way anyone there would let her see the Thompson case file.

Instead, she went to the New Orleans Police evidence vault and asked to look through their archives. As a matter of course, the policemen standing out in front of the evidence locker aren’t really supposed to let civilians come in and look around. Elisa showed up wearing a well-filled and largely unbuttoned blouse and convinced the police to look up the files in question. They gave her the chain of custody card for Thompson’s carjacking case, which indicated that the soiled tennis shoe and piece of pants fabric had been checked out by a junior assistant DA on April 3, 1985, and returned on April 10. On April 11, the same junior ADA checked the samples out again. This time, they were never checked back in.

The pants and shoe were gone, but the trail remained. When evidence is checked out, it is typically taken either to a hearing or trial where it can be examined or to the crime lab for testing. There had been no hearing in early April, so Elisa went over to the crime lab. Any original reports were long since destroyed, but the scientists there showed Elisa to their microfiche library and let her sit down and dig in.

How is new evidence uncovered? This is how: a private investigator hired by lawyers looking for a miracle charms her way into a lab and flips through thousands of pieces of microfiche looking for a blood test whose existence has been repeatedly denied by the DA’s office. She doesn’t blink, or wander, or doze off at the wrong time. And when she finds it, she makes several copies of it and gets the hell out of Dodge to call the lawyers.

Tenacity, boobs, and luck.

The blood test Elisa had found wasn’t supposed to exist. Both Dubelier, the prosecutor in charge at trial, and the prosecutor handling the appeal had stated in writing that there was no blood evidence in the DA’s possession. Yet the blood test had been sent to the DA’s office and put on prosecutor Jim Williams’ desk before Thompson’s armed robbery trial in May 1985—and never revealed to Thompson’s trial counsel. (Williams testified that he had no recollection of receiving the report, though one of his colleagues testified that he had sent it to Williams.) It showed that either the carjacker or the teenager in the car had blood type B. Both the teenager and John Thompson had blood type O.

This was the first revelation of Dubelier’s and Williams’ failure to turn over evidence that could exculpate Thompson, in violation of his constitutional rights under the 1963 Supreme Court case Brady v. Maryland . There would be other failures, as Banks and Cooney leveraged the discovery and an angry court of criminal justice judge to get unfettered access to the case files for the murder and armed robbery from the New Orleans police department and the Orleans Parish DA case files. From these, Banks and Cooney learned of several additional witnesses to the murder who had been interviewed by police, and were known to the DAs, who never told Thompson’s lawyers. The defense hired another private investigator to track down those witnesses, more than 15 years later, and get their stories.

Armed with those new witnesses, each of whom could have testified in 1985, Michael Banks and Gordon Cooney were finally able to get their client a new murder trial in 2003. There, John Thompson was acquitted in less than 35 minutes.

According to the Innocence Project, a national organization that represents incarcerated criminals claiming innocence, 36 men convicted in Orleans Parish during Connick’s 30-year tenure as DA have made allegations of prosecutorial misconduct, and 19 have had their sentences overturned or reduced as a result. (Connick retired in 2003.) The prosecutor who led the armed robbery trial and assisted in the murder trial, Jim Williams was one of the prosecutors whose work has come under scrutiny. In 1995, Esquire photographed him, for a piece on the death penalty, standing confidently in front of his desk with one of his favorite office decorations: a 12-inch-high, battery-powered (and operational) electric chair, complete with the mug shots of the five men he had personally prosecuted successfully in capital punishment cases. All five have subsequently been released or had their death sentences commuted to life due to procedural problems in their trials.

It’s clear that the prosecutors in Thompson’s carjacking case deliberately ignored the rules of evidence and that their strategy was to use the carjacking case to get the death sentence in his murder case. But it also became clear when Dubelier, Williams, and Connick were questioned under oath that they could not articulate the Brady rule, which sets forth the legal standard that determines when prosecutors must turn over evidence that could be used to show a defendant’s innocence. (Dubelier and Williams now make their livings as criminal defense attorneys, Dubelier for a large firm in Washington, D.C., and Williams as a sole practitioner outside of New Orleans.)

After listening to two days of testimony about how Connick ran his DA’s office, with Dubelier and Williams blaming each other and fumbling over conflicting and inaccurate explanations of what Brady requires, a federal court jury in New Orleans awarded Thompson a $14 million verdict in 2007. The jury found that his 18 years behind bars (14 of which he spent in solitary confinement on death row) were caused by Connick’s deliberate failure to train his prosecutors on their obligations to turn over exculpatory evidence.

The Orleans Parish DA’s office has appealed, saying in effect that Dubelier and Williams were rogue prosecutors and that Thompson’s case was at worst a single prosecutorial failure and does not satisfy the Supreme Court’s requirement of a “pattern and practice” of indifference to the rules. They argue that prosecutors should have absolute immunity from suit—that there simply are no circumstances serious enough to allow private citizens to recover damages from the DA’s office. This approach is being challenged not only by Thompson, but by a large stable of former prosecutors in amicus filings. The court will hear argument in the case, Connick v. Thompson , on Wednesday.

As John Thompson waits to find out whether his jury verdict will stand, the numbing parade of improper incarcerations marches past, with new cases in New Orleans being uncovered. Just last month, the Times-Picayune reported on the case of Booker Diggins, convicted in 1988 of armed robbery and rape. Two prosecutors in Connick’s office in 1988 “knew that blood and semen had been collected from the victim, along with a blood type that didn’t match the woman’s.” They failed to turn over this information to defense lawyers. Diggins was convicted of aggravated rape and received a sentence of life without parole.

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