The number of criminal cases in which a convicted defendant is later determined to be innocent is very small in America. Since 1989, DNA testing has led to the exonerations of 289 convicts in the United States - 17 of whom had served time on death row.
Even a thousand exonerations would pale in proportion to the 400 million non-traffic-related cases prosecuted over the past two decades, points out Scott Burns, executive director of the National District Attorneys Association.
But a database of 873 faulty convictions over the past 23 years - cases in which a wrong outcome has been acknowledged by prosecutors, judges or governors - has been compiled in a collaboration between the University of Michigan and Northwestern University. And even though the compilers point out the registry does not include many cases in which innocent parties plead guilty to a lesser charge in order to avoid more serious punishment, studying the patterns revealed by these 873 cases may still provide some useful guidance for police and prosecutors wishing to avoid repeating those mistakes.
Among the registry's major findings, as reported by USA Today this week:
- Of the 416 homicide exonerations examined, 64 percent were attributed, at least in part, to perjury or false accusations. Official misconduct by either prosecutors or police, including the withholding of evidence that could have tended to exonerate the suspect, was a contributor in 56 percent of the cases.
- In the registry's 203 sexual assault cases, 80 percent involved mistaken eyewitness identification.
Faulty witness identification was also a factor in 81 percent of the 47 erroneous robbery convictions.
Much of the misconduct involved the failure to disclose information or evidence that might have been helpful to defendants, said Michigan law professor Samuel Gross, the registry's editor.
Psychology professors have staged many experiments to reveal the unreliability of eyewitnesses - but judges and juries still tend to consider such testimony to be the gold standard of credibility. At the very least, police must institute safeguards which eliminate the possibility of an investigating officer suggesting to a witness - even unintentionally - that the suspect in custody may be the culprit.
But part of the problem here is an obvious psychological characteristic: Prosecutors tend to be competitive individuals who strive hard to win. Some cases - the murder trial of O.J. Simpson comes to mind - can become so emotional that prosecutors become visibly teary-eyed, drop into a sullen funk, or actually apologize if they fail to win a conviction.
Given that police and prosecutors believe they've got the proper suspect on trial - else they would not have proceeded - it's an obvious temptation to withhold evidence that might tend to exonerate, on grounds that it would "merely help the guilty party go free."
A greater faith in the system is required. Yes, both sides must strive their utmost within the bounds of propriety and law. But an acquittal is not always a miscarriage of justice. District attorneys must guard against a culture in which promotions are based solely on victories. Sometimes the prosecutor does his or her job just fine - and the jury still decides no conviction is warranted.
The number of miscarriages of justice remains small. But 873 is still too many. This study could go a long way toward reducing that number.