by the University of Michigan
ANN ARBOR, Mich.—Criminal justice scholars often say that the true number of false convictions is unknown, but a recently published University of Michigan study challenges that belief.
Among defendants sentenced to death in the United States since 1973, at least 2.3 percent – and possibly more – were wrongfully convicted, said U-M law expert Samuel Gross.
If defendants who were sentenced to prison had been exonerated at the same rate as those who were sentenced to death, there would have been nearly 87,000 non-death-row exonerations in the U.S. from 1989 through 2003. Only 266 were reported during that time frame, he said.
“The main thing we can safely conclude from exonerations is that there are many other false convictions that we have not discovered,” said Gross, whose research focuses on the death penalty, false convictions and eyewitness identification.
He co-authored the by José de la Isla study with Barbara O’Brien, an assistant law professor at Michigan State University.
“In addition, a couple of strong demographic patterns appear to be reliable,” the study indicated. “Black men accused of raping white women face a greater risk of false conviction than other rape defendants; and young suspects, those under 18, are at greater risk of false confession than other suspects.”
Since 1989, almost all of the exonerations fall into three categories:rape convictions because of post- conviction DNA testing; murder convictions—and especially death sentences—which are sometimes subjected to detailed post-conviction reinvestigation;and drug and gun possession convictions that were produced by concerted programs of police perjury that later unraveled.
Gross, the Thomas and Mabel Long Professor of Law, said capital exonerations are less common for defendants convicted of murdering more than two victims. They are more common for those convicted of murdering children.
These patterns could reflect differences in the quality of the evidence and the likelihood of error based on the age and number of victims, Gross said.
“The low exoneration rate among multiple murder cases may simply mean that defendants who are convicted of killing more than two victims are less likely than others to linger on death row or have their death sentences reduced,” he said.
Capital exonerations also appear to be more frequent among cases in which the criminal investigation was unusually difficult, or where common items of direct or circumstantial evidence of guilt were missing. Other patterns include:
• Exonerated defendants were less likely to have serious criminal records than executed defendants. Gross said he expected an opposite result because the police might attach too much weight to a suspect’s violent history and pursue weak, and sometimes false, cases against plausible-seeming suspects who committed other crimes.
• The confessions are three and a half more common among the accused executed (52 percent) than those exonerated (15 per cent). Many accused for murder confess, and the majority of the confessions are real. Without a confession,especially one that is voluntary, increases the risk of false condemnations.
• The rule for the confessions
repeats itself in the trial. Some accused for crimes that carry capital punishment do not dispute actively their fault before the court. These tacit admissions of fault are more common among the accused executed (38 percent) than between the exonerated ones (13 percent) that were sentenced to death. In other words, among the prisoners sentenced to death the risk that their convictions had been an error is greater in cases in which the accused affirmed actively his innocence during the judgment.
• The clearest proof that a difficult investigation increases the risk of error is the time that passes between the crime and the arrest of the accused. In average, the investigations before to the arrest, in cases with judgment of death penalties that were then exonerated, were a two times and longer than average in the cases that ended in execution.
