From the Death Penalty Information Center,
A new law review, “Convicting the Innocent,” by Samuel Gross, explores the rate of false convictions among death sentences and demographical and procedural predictors of such errors. Gross’ research shows the exoneration rate is 2.3% for “inmates who had been on death row at least 15 years as of 2004 and for those who had been on death row for at least 20 years.” Gross continues, “This figure – 2.3% - is the actual proportion of exonerations for death sentences imposed in the United States between 1973 and 1979.” He concludes, “The proportion of capital exonerations is almost certainly an underestimate of the true rate of false capital convictions.”
The obvious question, then, which Gross hints at, is how many innocent people have been executed without being exonerated. The United States has executed 1,138 people with another 3,308 waiting on death row. At 2.3%, that would mean over 100 people have been falsely convicted and sentenced to death.