More than Four Percent of Defendants Sentenced to Death are Innocent, New Study in Proceedings of National Academy of Sciences Shows
Number of innocent people is likely more than double number of those actually exonerated and freed from death row
At least 4.1 percent of defendants sentenced to death in the United States are innocent, according to new research released Monday. The article, Rate of False Conviction of Criminal Defendants who are Sentenced to Death, is co-authored by Samuel Gross, Editor of the National Registry, and published in the Proceedings of the National Academy of Sciences, one of the world's more respected and cited scientific journals. It has already received media attention from outlets such as the Associated Press and Time.
"[N]o process of removing potentially innocent defendants from the execution queue can be foolproof. With an error rate at trial over 4%, it is all but certain that several of the 1,320 defendants executed since 1977 were innocent," the study concludes.
"This study provides the first rigorous estimate of the rate of conviction of innocent criminal defendants in any context. It shows that the number of innocent people sentenced to death is more than twice the number of inmates actually exonerated and freed by legal action," said Bruce Levin, Ph.D., an expert in statistics who did not participate in the research but is familiar with the study. Dr. Levin is Professor and Past Chair of the Department of Biostatistics at the Mailman School of Public Health, Columbia University.
1.6 percent of those sentenced to death since 1973 in the U.S. – 138 prisoners – have been exonerated and released because of innocence. But many other innocent capitial defendants are missed. "The great majority of innocent people who are sentenced to death are never identified and freed. The purpose of our study is to account for the innocent defendants who are not exonerated," said Professor Gross.
A major reason that many innocent capital defendants are not exonerated is that they are removed from death row but remain in prison. Lawyers, courts and governors focus a great deal of attention and time on reviewing that cases of prisoners who are on death row in order to reduce the risk of executing innocent people. But most death row prisoners have their sentences reduced to life in prison in the process of appellate review.
When that happens, the threat of execution is removed and far less time and resources are devoted to seeking out cases of possible innocence. As a result, an innocent defendant who might well be exonerated and released if he remained on death row for many years is likely to die in prison if he is resentenced to life.
To address this issue, the researchers employed a statistical technique called survival analysis that is commonly used in medicine. Survival analysis produces an estimate of the percentage of death-sentenced defendants who would be exonerated if they all remained indefinitely on death row and therefore subject to the exacting process for identifying innocent defendants that is applied to those who remain under threat of execution. The researchers concluded that their finding – 4.1% – is "a conservative estimate of the rate of false conviction among death sentences in the United States."
In addition to Professor Gross, that authors of the study are Professor Barbara O'Brien, Ph.D., Michigan State University College of Law; Chen Hu, Ph.D., Senior Biostatistician, American College of Radiology Clinical Research Center and Adjunct Scholar, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine; and Edward H. Kennedy, Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine.
CNN "Death Row Stories" Brings Death Row to Primetime
On March 9, CNN premiered the first episode of an eight part series entitled "Death Row Stories." Each episode is a one-hour documentary which attempts to unravel the truth behind a different capital murder case. The series is narrated by Susan Sarandon.
Three of the first five episodes featured exonerees listed in the Registry. John Thompson was sentenced to death in Louisiana in part due to extreme prosecutorial misconduct. Official misconduct is present in nearly half of all exonerations in the Registry and in 70% of death row exonerations.
Joseph D'Ambrosio, who spent over twenty years wrongfully incarcerated, was exonerated through the relentless efforts of a priest. D'Ambrosio's co-defendant is still fighting for freedom in Ohio.
While Gloria Killian was never sentenced to death, threats of the death penalty were used when interrogating her and her co-defendants. Over 10% of exonerees, including Killian, have a co-defendant who implicates them in a crime.
The two other people featured to date are not in the Registry. One man is fighting for his freedom and the other took a plea bargain for his release (see our criteria for exoneration).
The series will return on July 13 at 9pm ET/PT, but you can catch up on highlights from past episodes here.