The study concludes that were all innocent people who were given death sentences to be cleared of their offences, the exoneration rate would rise from the actual rate of those released – 1.6% – to at least 4.1%. That is equivalent in the time frame of the study, 1973 to 2004, of about 340 prisoners – a much larger group than the 138 who were exonerated in the same period. The approach allows researchers to “actually come up with a valid estimate of the rate of false convictions—knowing something that people say [in criminal justice] is not knowable,” says study author Samuel Gross, a law professor at the University of Michigan Law School and editor of the National Registry of Exonerations, a U.S.-focused exoneration database. The study, published in a prestigious journal, the Proceedings of the National Academy of Sciences, does not solve perhaps the greatest single riddle of the death penalty: how many innocent people have actually been put to death in modern times. For more on death penalty considerations, see Scientific American’s editorial in the May edition of the magazine that details how the use of drugs to carry out capital punishment is inadvertently putting medical patients at risk. Gross and his co-authors estimate that 36% of all those sentenced to death between 1973 and 2004 – some 2,675 people – were taken off death row after doubts about their convictions were raised. 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. 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. Because they are no longer under the threat of execution, they are no longer treated as priorities within the criminal justice system.
– At least 4.1% of people sentenced to death in the US are innocent, a new report warns—and most of them end up neither executed nor exonerated, but serving life behind bars. Researchers say that at a conservative estimate, one in 25 of the thousands of people condemned to death between 1973 and 2004 is innocent and while 138 were exonerated and some were almost certainly executed, up to 200 were taken off death row and are serving life for murders they didn't commit, the Guardian reports. The researchers—who employed a statistical method often used to assess survival rates of patients treated with new medical therapies—say being moved off death row tends to reduce the chances of exoneration, as the inmates' cases are no longer treated as priorities and they have fewer options for appeals, Scientific American reports. "The great majority of innocent defendants who are convicted of capital murder in the United States are neither executed nor exonerated," the study concludes. "They are sentenced, or re-sentenced to prison for life, and then forgotten."