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DNA Tests Suggest Wrongful Convictions Could Top 10% in Closed Sexual Assault Cases

Document date: June 18, 2012
Released online: June 18, 2012

Abstract

This study analyzed the results of new DNA testing of old physical evidence from 634 sexual assault and homicide cases that took place in Virginia between 1973 and 1987 in the first study of the effects of DNA testing on wrongful conviction in a large and approximately random sample of serious crime convictions. The study found that in five percent of homicide and sexual assault cases DNA testing eliminated the convicted offender as the source of incriminating physical evidence. When sexual assault convictions were isolated, DNA testing eliminated between 8 and 15 percent of convicted offenders and supported exoneration. Past estimates generally put the rate of wrongful conviction at or less than three percent.


Contact: Matthew Johnson, (202) 261-5723, mjohnson@urban.org

Washington, D.C., June 18, 2012 -- Wrongful convictions for homicide and sexual assault are more prevalent than once thought, according to a groundbreaking new Urban Institute study. However, testing DNA evidence can help identify and correct some of these cases and prevent future wrongful convictions.

The Justice Policy Center-led study estimated how many convicted offenders would be exonerated if archived DNA evidence were tested. Researchers John Roman, Kelly Walsh, Pamela Lachman, and Jennifer Yahner analyzed the results of new testing of archived DNA from 634 sexual assault and homicide cases that took place in Virginia between 1973 and 1987. Their study was the first to test DNA for a large and unbiased sample of serious crime convictions.

The study found that in 5 percent of homicide and sexual assault cases, DNA testing eliminated the convicted offender as the source of incriminating physical evidence. When sexual assault convictions were isolated, DNA testing eliminated between 8 and 15 percent of convicted offenders and supported exoneration.

Past estimates generally put the rate of wrongful conviction at 3 percent or less.

Tests of DNA evidence in old sexual assault cases are likely more effective than in other violent crimes, the researchers concluded, because the evidence, particularly semen, is more durable. Such evidence from sexual assault cases, they said, could implicate or exclude a suspect 54 percent of the time, compared with less than 10 percent in homicides with no sexual assault.

“These findings are important not only because they highlight the scale of wrongful convictions, but also because there are hundreds of victims in Virginia -- and potentially thousands throughout the United States -- for whom justice was not served,” stated lead researcher John Roman.

The DNA Post-Conviction and Actual Innocence study was funded by the U.S. Department of Justice’s National Institute of Justice.

The Urban Institute is a nonprofit, nonpartisan policy research and educational organization that examines the social, economic, and governance challenges facing the nation. It provides information, analyses, and perspectives to public and private decisionmakers to help them address these problems and strives to deepen citizens’ understanding of the issues and trade-offs that policymakers face.



Topics/Tags: | Crime/Justice


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