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The dark side of DNA Add to ...

Gregory Turner feared he was bound for life in prison after an RCMP lab reported odds of 163 trillion to 1 that a tiny amount of DNA on his gold ring could have come from anybody but a 56-year-old woman found murdered in rural Newfoundland.

The only real evidence in a first-degree murder charge against Mr. Turner, the golden sheen of DNA appeared certain to become a silver bullet in the hands of the Crown.

"I told my lawyer, Jerome Kennedy, that there was no way in the world it was true," Mr. Turner recalled in an interview. "He believed me. He said that I was too stupid to commit that crime and leave no evidence."

A lucky hunch by Mr. Kennedy - now Newfoundland's Minister of Health - saved Mr. Turner from a life behind bars. He sought the name and DNA profile of every technician who had worked at the RCMP lab. It turned out that the technician who had tested the ring had also been working on the victim's fingernails a few inches away, creating a strong possibility of contamination.

The technician conceded at Mr. Turner's 2001 trial that she had also contaminated evidence in two previous cases. In another disturbing twist, it emerged that she had mistakenly contaminated Mr. Turner's ring with her own DNA, causing police to waste considerable time on a futile search for a presumed accomplice.

Mr. Turner still has nightmares. "I remember the judge saying that he was denying me bail based on the likelihood I'd be convicted based on a DNA match," he said. "I think DNA can be good, but its only as good as the people who perform it. I spent 27 months in jail for a crime I didn't do."

In just 20 years, DNA has become a staple of crime-lab analysis, capturing the imagination of scriptwriters and anchoring thousands of criminal convictions. Its record of accuracy is superb - at least, when samples are collected and analyzed under reliable conditions by experts.

But cautionary tales such as Mr. Turner's are starting to pile up. As scientists are able to analyze smaller and smaller portions of DNA, the spectre of DNA evidence being planted at crime scenes becomes a more chilling possibility. There is also an emerging understanding that some individuals may elude detection because they have more than one DNA profile; that lab botch-ups happen with distressing regularity; and that overly dogmatic or underqualified courtroom experts represent a constant danger.

In a legal paper he wrote in 2004, Mr. Kennedy described the case as a blow to the scientific objectivity of the RCMP lab, as well as the credibility of future DNA reports. "In this case, bad science was exposed," he said. "...This case is an example of how untested scientific techniques, human error and bad science could have combined to obtain a conviction for murder."

Last year, University of Virginia law professor Brandon Garrett and Peter Neufeld, co-founder of the Innocence Project, found that three of 156 U.S. individuals ultimately exonerated in serious crimes had been wrongly convicted because of DNA errors. In one case, a technician grossly overstated evidence. Another featured lab contamination. The third wrongful conviction came after senior analyst Fred Zain gave evidence in court he knew to be false.

Prof. Young describes the Zain case as "a classic example of why you can't simply roll over and play dead in the face of science." After his shortcomings at the Virginia State Police Crime Laboratory were discovered, Mr. Zain left and became head of a medical examiner's lab in Texas. His errors became one of several problems the state ultimately faced.

"They have had to reopen hundreds of cases in Texas because of the discovery of horrible preservation and contamination issues," said Alan Young, a professor at York University's Osgoode Hall Law School. "They had to literally shut down a lab in Houston because it was generating so many false results."

In other cases, the errors were inadvertent but no less damaging. Several years ago, a developmentally handicapped girl in Australia was linked to the murder of a toddler hundreds of kilometres away based on DNA found on the victim's clothing. It turned out the suspect had recently reported being sexually assaulted. A condom connected with the assault was being tested in a forensic lab at the same time as the murdered child's clothing.

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