Thanks for the link. Scientific American looks at the study.
https://www.scientificamerican.com/a...lly-convicted/
It doesn't actually prove that anyone was posthumously found innocent. It worked a bit differently than that.
The study, led by a team of lawyers and statisticians, examined data on both 7,482 defendants who were given death sentences between 1973 and 2004 and death row exonerations during that time. By applying survival analysis—a statistical method often used to calculate how well new treatments help patients survive—they determined how often a prisoner under threat of execution was exonerated. The method usually tracks patients to see if a new therapy prolongs the period of time until a person dies from the illness in question but it can also be applied to policy questions that have clear end points. In this study the end point of tracking was exoneration (being found innocent and freed) or the actual execution. “Survival” was defined as remaining in prison. The “therapy” here would be removal of the threat of execution.
Here’s how their analysis works. It says that if all death-sentenced defendants remained under this sentence indefinitely, as opposed to being taken off death row due to being resentenced to life in prison or their fate being artificially cut off by the study ending, then 4.1 percent of those prisoners would have otherwise been exonerated. (And being exonerated and freed by legal action here is used as the best proxy for innocence.) The analysis also takes into account other occurrences such as suicide or death of a prisoner from natural causes. The number of false convictions among the death-sentenced has been particularly hard to estimate, Gross says, because many prisoners who are on death row are eventually moved off of it but remain in prison, which often reduces their chances of exoneration.
The issue affects a significant number of people. Since 1973 144 death-sentenced defendants have been exonerated in the U.S. But Gross says that the analysis indicates that at least 340 people would have been put to death unjustly in that same time period. “There are no other reliable estimates of the rate of false conviction in any context,” the researchers wrote in the study, published online on April 28 in Proceedings of the National Academy of Sciences.