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Study Finds Wrongful Convictions in 11.6 Percent of Sexual Assault Cases from Pre-DNA Testing Era

A recent study by the Urban Institute estimated that “wrongful convictions in cases with a sexual assault component occurred at a rate of 11.6 percent.”

While the research was based on 714 murder and felony sexual assault cases across 56 Virginia circuit courts, it concluded that the wrongful conviction rate was “not significantly different from other states, suggesting that findings of research may be extended – with caution – to other jurisdictions.”

The study was made possible by a grant from the U.S. Department of Justice’s National Institute of Justice, and allowed the Urban Institute to follow up on a 2012 study where it had applied “post-conviction DNA testing to a large set of convictions, regardless of any existing claims or evidence of wrongful convictions.”

That earlier study examined 715 cases involving murder and sexual assault convictions in Virginia between 1973 and 1987. It determined that five to eight percent of the convictions were wrongful. Each of those cases still had existing biological evidence, which was contrary to Virginia’s policy at the time to destroy such evidence. One forensic seriologist, Mary Jane Burton, and another person she trained, had physically attached biological samples to hard copy laboratory files. That evidence has aided in the exoneration of some Virginia prisoners.

The more recent study, released in September 2017, collected information on 714 cases – almost all from the 2012 research – from original courthouse files. The research team was composed of groups that independently reviewed each conviction to determine if the trial transcripts and other documents required a revision of the case’s previous classification of whether the DNA test results were exculpatory, inculpatory, supportive of exoneration or exculpatory but insufficient for exoneration. The team found five additional wrongful convictions that had not been included in the original study, and reclassified 14 cases as exculpatory but insufficient that were previously found to be supportive of exoneration.

The study isolated 231 convictions with a sexual assault component with determinate post-conviction DNA testing results, and found that 29 of those convictions, or 12.6 percent, yielded exculpatory DNA evidence supportive of exoneration. Applying probability weights, the rate was corrected to an upper bound of 11.6 percent for sexual assault cases.

The research team also examined 1985 convictions from 43 states to determine if the wrongful conviction rate could be generalized to other states. Based on similar case dismissal rates, it concluded the estimated rate of wrongful convictions could be applied to other jurisdictions.

Over 300 people have been exonerated in the United States for crimes that occurred in the pre-DNA testing era, a 2016 report by the Innocence Project found. Based on this study’s results, many more people were likely wrongfully convicted during that time period.

In June 2016, the Center for Prosecutor Integrity (CPI) launched its Wrongful Convictions of Sexual Assault Program to address cases in which defendants are falsely accused or convicted of sex-related offenses.

“Forty years ago, a woman who had been raped encountered numerous obstacles to justice,” said CPI director E. Everett Bartlett. “Now, the situation is reversed. A man accused of rape may find it difficult, or even impossible to prove his innocence.” 

Sources: “Estimating The Prevalence of Wrongful Convictions,” Urban Institute (Sept. 2017);


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