Wrongful Convictions

III. Size and Scope of the Wrongful Conviction Problem

If wrongful convictions were rare, they could be downplayed as inevitable failings of a complex human system. If they are frequent and are linked to systemic problems, then they pose a challenge to the fairness and accuracy of the justice system that calls for a public response. The issue is controversial. Some prosecutors and judges believe the number of wrongful convictions to be vanishingly small and have offered an estimate of approximately 260 a year or an error rate of 0.027% (or 0.00027). This figure is a mistaken interpretation of a study conducted by Professor Samuel Gross and colleagues that counted 340 known exonerations between 1989 and 2003 (Gross, Jacoby, Matheson, Montgomery, & Patil, 2005). Critics fail to note that an exoneration is not the same as a wrongful conviction (although the terms are loosely used as equivalents). Gross et al. (2005) defined an exoneration as an official act declaring a previously convicted defendant not guilty, by means of (a) a governor’s pardon on the basis of evidence of innocence; (b) a court dismissing criminal charges on the basis of new evidence of innocence (e.g., DNA); (c) a defendant being acquitted on retrial after an appeal, on evidence of factual innocence; or (d) a state’s posthumous acknowledgment that a defendant who had died in prison was innocent. The study, however, demonstrated that the 340 exonerations it catalogued were the tip of an iceberg, with the number of wrongful convictions probably reaching into the thousands.

Most known exonerations have occurred in murder and rape cases rather than more numerous crimes, such as robbery, for which unreliable eyewitness identification is the only evidence. This is so partly because DNA evidence is available in most rape cases (although 60% of known exonerations were revealed by means other than DNA testing). High-stakes capital cases also generate greater assistance to avoid executions. It is likely that more errors occur in assault, robbery, and burglary convictions based on erroneous eyewitness identification and circumstantial evidence. Studies of wrongful convictions in death penalty cases since 1973 (when the modern era of capital punishment began), as to which careful statistics are kept by the government, have estimated “wrong person” wrongful convictions at 1% to 3.5%. In Illinois, of the 289 persons sentenced to death between 1973 and 2003, 17 (or 5.9%) were exonerated and released.

Surveys of state judges, prosecutors, defense lawyers, and police officials have provided an alternate estimate of wrongful convictions—of about 1%. Although police and prosecutors give lower estimates than judges and defense lawyers, in light of what is now known about wrongful convictions a 1% felony error rate is plausible. On the basis of slightly more than 1 million state court adult felony convictions in 2004, and prison and jail rates of 40% and 30%, respectively, this rate translates to an estimated 10,790 adults wrongly convicted, of whom 4,316 were sent to prison and 3,237 wrongly jailed in 2004.

The number of wrongly convicted persons cannot be known with certainty, because no federal or state agency keeps track of exonerations, let alone wrongful convictions. Many news stories, reports, and books fairly describe wrongful convictions in detail, although not all of these wrongful convictions resulted in formal exonerations. In some of these cases, prosecutors insisted that the original verdict was accurate despite strong new evidence of factual innocence, further clouding an understanding of wrongful convictions.

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