It is hard to know what is most shocking about the case of mentally disabled Henry Lee McCollum*, exonerated and released earlier this month after spending 30 years on death row in North Carolina. It is shocking that his mental disability did not preclude the death penalty in his case. It is perhaps even more shocking that he was questioned by police for five hours under extreme pressure until he produced a confession, to make the interrogation stop. It is scandalous that his confession must have been fed to him by the police. It is disturbing that police hid evidence that was favourable to him. It is shameful that the police’s exclusive focus on McCollum prevented them from arresting the true murderer, who was thus free to commit another murder.

The distressing list extends further. One of the US Supreme Court judges, Justice Antonin Scalia, specifically cited McCollum’s case as an example of a crime so heinous that it would be hard to argue against lethal injection for him. (It is worth noting that Justice Scalia also believes that execution is a just end for anybody who eventually proves his innocence, provided he or she originally had a fair and full trial.) And it was McCollum’s image that the North Carolina Republican Party selected and publicized, as part of their 2010 campaign to demonstrate the dangers of being soft on crime.

But what perhaps seems most bizarre is that even after DNA testing has proved conclusively that a different man was the murderer, the original district attorney in McCollum’s case, Joe Freeman Britt, remains convinced of McCollum’s guilt.

In his book, Injustice: Life and Death in the Courtrooms of America (Vintage, 2013) Clive Stafford Smith advances a view about prosecutors that could explain this misplaced zeal:

“As a matter of human nature, it is probably inevitable that those who spend their lives sending people to prison become increasingly converted to this notion of prosecutorial infallibility. It would be difficult to drive to work every day pondering how many innocent people you might deprive of liberty today. There is a second self-selection procedure, whereby those who continue to harbour doubts move on from the prosecutor’s office quite rapidly. The remainder confirm each other’s biases around the coffee machine until the wagons are fully circled.”

Prosecutors’ prejudices are strengthened by legal protection. The ‘doctrine of sovereign immunity’ makes it impossible to sue a prosecutor who frames an innocent person for capital murder.

Just like McCollum, Willie Jerome Manning has walked a long and difficult road to gain the DNA testing that could exonerate him and may identify a murderer. Like McCollum, Willie has suffered from hugely negative publicity. Is it possible that, as happened with McCollum, Willie’s unwarranted notoriety derives ultimately from prosecutors’ misplaced belief in their own infallibility?

*McCollum was convicted alongside his mentally disabled half-brother, Leon Brown, who was sentenced to life imprisonment for rape. Brown was only 15 at the time of the crime. He was exonerated and released at the same time as McCollum.