1 in a million? Wrongful conviction experts study DNA odds

HOUSTON (AP) — A flawed way of calculating the odds that a defendant left DNA at a crime scene is the next target of prosecutors and criminal justice advocates working together in Texas to weed out wrongful convictions.

Thousands of cases are being reviewed for testimony about DNA odds that may have been given using outdated guidelines that inflated the likelihood a defendant had touched a murder weapon or another piece of evidence, the Houston Chronicle reported (http://bit.ly/1PJu8WQ ).

In one Galveston homicide case, the original analysis of a screwdriver believed to have been used in the incident suggested there was a 1 in 290 million chance that it had been touched by a different person of a similar ethnic background to the defendant, German Perez-Vasquez.

When the screwdriver was analyzed under newer guidelines issued several years ago, that probability was calculated as 1 in 38.

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The review is the latest collaboration between groups such as the Innocence Project and state agencies including the Texas Forensic Science Commission, which have studied other sources of courtroom errors such as faulty fire science and bite mark evidence.

Innocence Project co-founder Barry Scheck told the newspaper that of his discussions with forensic scientists nationally about the DNA issues, “Texas is the only place that’s systematically trying to correct it.”

Bob Wicoff, who heads the appellate division of the Harris County Public Defender’s Office, will lead a statewide effort to review potential cases, with a $400,000 grant from the Texas Indigent Defense Commission.

Wicoff said he plans to eventually have trainings for lawyers throughout the state to discuss the new science.

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“It’s impossible to say how many cases we’ll have to review,” Wicoff said. “but it could take a long, long time.”


Information from: Houston Chronicle, http://www.houstonchronicle.com