A 2013 study of false convictions says that Justice Scalia’s estimate was “silly”, conservatively, 4.1% of people sent to death row are innocent, and the majority of innocent but convicted capital defendants are neither executed nor exonerated.
The report concludes:
“We use survival analysis to model this effect, and estimate that if all death-sentenced defendants remained under sentence of death indefinitely, at least 4.1% would be exonerated. We conclude that this is a conservative estimate of the proportion of false conviction among death sentences in the United States.”
“We do know that the rate of error among death sentences is far greater than Justice Scalia’s reassuring 0.027% (6). That much is apparent directly from the number of death row exonerations that have already occurred. Our research adds the disturbing news that most innocent defendants who have been sentenced to death have not been exonerated, and many—including the great majority of those who have been resentenced to life in prison—probably never will be.”
“This is only part of a disturbing picture. Fewer than half of all defendants who are convicted of capital murder are ever sentenced to death in the first place (e.g., 49.1% in Missouri as in ref. 24, 29% in Philadelphia as in ref. 25, and 31% in New Jersey as in ref. 26). Sentencing juries, like other participants in the process, worry about the execution of innocent defendants. Interviews with jurors who participated in capital sentencing proceedings indicate that lingering doubts about the defendant’s guilt is the strongest available predictor of a sentence of life imprisonment rather than death (27). It follows that the rate of innocence must be higher for convicted capital defendants who are not sentenced to death than for those who are. The net result is that the great majority of innocent defendants who are convicted of capital murder in the United States are neither executed nor exonerated. They are sentenced, or resentenced to prison for life, and then forgotten.”
Read the Study in full here : Rate of false conviction of criminal defendants who are sentenced to death – Proceedings of the National Academy of Sciences of the United States of America.