According to a collaborative research project initiated by the University of Michigan Law School and published earlier this year in PNAS, 4.1 percent of all death sentences in the U.S. are the result of false convictions.
The researchers, Samuel R. Gross, Barbara O’ Brien of the University of Michigan, Chen Hu of American College and Edward H. Kennedy of University of Pennsylvania, consider their estimate a conservative one.
The report examined data on all defendants sentenced to death between the years 1973-2004. Of those 7,482 defendants, 943 were executed, 298 died while on death row and 3,449 remained on death row. A total of 117 death row defendants were exonerated, while 2,675 defendants were removed from death row but not exonerated.
The report said that the high rate of exonerations appears to be driven by the threat of execution. “Everyone from defense lawyers to innocence projects to governors and state and federal judges is likely to be particularly careful to avoid the execution of innocent defendants.” However, once defendants are removed from death row and resentenced to life imprisonment, the likelihood of exoneration drops sharply because the intensive search for possible errors is largely abandoned once the threat of execution is removed.”
The researchers used multiple methods of analysis to reach a final conclusion that if all death-sentenced defendants were to remain under sentence of death indefinitely, at least 4.1 percent would be exonerated.
The report is careful to point out that their estimate of false convictions in death penalty cases cannot be applied to all criminal convictions. The rate of erroneous convictions overall is often described as a “dark figure”; it is an important measure of the performance of the criminal justice system that is “not merely unknown, but unknowable.”
However, some heavy thinkers try to figure it out. These researchers noted that “in 2007, Justice Antonin Scalia wrote in a concurring opinion in the Supreme Court that American criminal convictions have an “error rate of .027 percent – or, to put it another way, a success rate of 99.973 percent.”
“This would be comforting, if true,” said the report. “In fact, the claim is silly. Scalia’s ratio is derived by taking the number of known exonerations at the time, which were limited almost entirely to a small subset of murder and rape cases, using it as a measure of all false convictions (known and unknown), and dividing it by the number of all felony convictions for all crimes, from drug possession and burglary to car theft and income tax evasion.”
To accurately estimate the number of all false convictions, a researcher would need “a well-defined group of criminal convictions within which we identify all mistaken convictions, or at least most. It is hard to imagine how that could be done for criminal convictions generally, but it might be possible for capital murder,” the report said.
“Death sentences represent less than one-tenth of 1 percent of prison sentences in the United States,” according to the report. “But they accounted for about 12 percent of known exonerations of innocent defendants from 1989 through early 2012.”
Such exonerations are achieved because more attention and resources are devoted to death penalty cases than to other criminal prosecutions, both before and after conviction.
“The vast majority of criminal convictions are not candidates for exoneration because no one makes any effort to reconsider the guilt of the defendants. Approximately 95 percent of felony convictions in the United States are based on negotiated pleas of guilty (plea bargains) that are entered in routine proceedings at which no evidence is presented. Few are ever subject to any review whatsoever,” the report said. “Most convicted defendants are never represented by an attorney after conviction, and the appeals that do take place are usually perfunctory and unrelated to guilt or innocence.”
Death sentences are different. They result from a trial by jury and can be reviewed on appeal, often repeatedly. Most inmates on death row continue to have lawyers for the duration of their stay. Such attention and resources mean that “false convictions are far more likely to be detected among those cases … than in any other category of criminal convictions.”
The report stresses that the proportion of death-sentenced inmates who are exonerated understates the rate of false convictions among death sentences because the intensive search for possible errors is largely abandoned once the threat of execution is removed.
It is important to note that 35.8 percent of the death-sentenced defendants from1973 to 2004 were removed from death row but remained in prison after their capital sentences or the underlying convictions were reversed or modified.
The point was made that “except for those who are exonerated – and a very small group who are resentenced to lesser penalties and eventually released – all prisoners who are sentenced to death do ultimately die in prison.”
As to the question, “how many innocent defendants have been put to death?” the researchers believe the number is comparatively low. “Our data and the experience of practitioners in the field both indicate that the criminal justice system goes to far greater lengths to avoid executing innocent defendants than to prevent them from remaining in prison indefinitely.”
The report continued, “However, no process of removing potentially innocent defendants from the execution queue can be foolproof. With an error rate at trial over 4 percent, it is all but certain that several of the 1,320 defendants executed since 1977 were innocent.”
The researchers added “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.”
The report went on: “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.”
Interviews with jurors indicate that “lingering doubts about the defendant’s guilt” make them likely to choose a sentence of life in prison rather than death.
“The net result” said the researchers, “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.”