John Thompson spent 18 years in a Louisiana prison, 14 of them in a windowless, six-by-nine-foot death row cell. He was a few weeks away from death by lethal injection when his life was saved by a bloody scrap of cloth.
Although four prosecutors in the Orleans Parish District Attorney's Office knew about this evidence, Thompson didn't learn of it until 14 years after his death sentence, when an investigator hired by his pro bono lawyers discovered a crucial crime lab report. Because they enjoy absolute immunity from liability for their trial-related work, these prosecutors cannot be forced to compensate Thompson for the egregious misconduct that led to his 18-year ordeal, and in March the U.S. Supreme Court said their office cannot be held responsible either.
In 1985 Thompson, then 22, was arrested for the murder of a hotel executive who was robbed and shot outside his New Orleans home. After Thompson's picture appeared in a local newspaper, three people who were victims of an armed robbery a few weeks after the murder thought they recognized their assailant. Unbeknownst to Thompson or his attorney, the robber was cut while scuffling with one of his victims, leaving blood on the man's pants. The blood was type B; Thompson's blood type is O. He never got a chance to present this exculpatory evidence because his prosecutors never turned it over, even though he had a due process right to see it under Brady v. Maryland, a 1963 Supreme Court decision.
The prosecutors decided to try Thompson for the robbery first, hoping to prevent him from taking the stand at his murder trial (since that would allow them to impeach his credibility by mentioning the earlier conviction) and to enhance the likelihood of a death sentence. They succeeded on both counts.
After the concealed evidence came to light, Thompson's robbery conviction was thrown out, and he won a new murder trial, during which he presented 13 pieces of evidence that, like the blood test, had been withheld by prosecutors. The jury acquitted him after deliberating for half an hour.
In 2003 Thompson won a $14 million award from a federal jury that concluded District Attorney Harry Connick Sr. had acted with "deliberate indifference" by failing to train his underlings in their constitutional obligations. The U.S. Court of Appeals for the 5th Circuit upheld that award in 2008. The Supreme Court overturned the 5th Circuit's decision, finding that Thompson had failed to prove a pattern of disregard for constitutional rights in Connick's office that was tantamount to official policy.