Apparently, there is a Center on Wrongful Convictions at the Northwestern U. Law School mentioned by Grann.
In the summer of 1660, an Englishman named William Harrison vanished on a walk, near the village of Charingworth, in Gloucestershire. His bloodstained hat was soon discovered on the side of a local road. Police interrogated Harrison’s servant, John Perry, and eventually Perry gave a statement that his mother and his brother had killed Harrison for money. Perry, his mother, and his brother were hanged.
Two years later, Harrison reappeared. He insisted, fancifully, that he had been abducted by a band of criminals and sold into slavery. Whatever happened, one thing was indisputable: he had not been murdered by the Perrys.
Here are the final words of Josh Willingham, whose homicide may well become the first acknowledged by any state to have been executed in error:
“The only statement I want to make is that I am an innocent man convicted of a crime I did not commit. I have been persecuted for twelve years for something I did not do. From God’s dust I came and to dust I will return, so the Earth shall become my throne.”