The Urban Institute (UI) published the results of a study, said to be the first of its kind, showing the” effects of DNA testing on wrongful convictions in a large and approximately random sample of serious crime convictions.”
The study’s abstract states:
“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.”
According to the UI media release on the study, Post-Conviction DNA
Testing and Wrongful Conviction,authored by John Roman, Kelly Walsh, Pamela Lachman, and Jennifer Yahner:
Wrongful convictions for homicide and sexual assault are more prevalent than once thought.
Testing DNA evidence can help identify and correct some of these cases and prevent future wrongful 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.
Source: Urban Institute
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