Brendan I. Koerner at Wired, explores the ramifications of the authorities requesting DNA from ancestry sites:
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Mitch Morrissey, Denver’s district attorney and one of the nation’s leading advocates for familial DNA searching, stresses that the technology is “an innovative approach to investigating challenging cases, particularly cold cases where the victims are women or children and traditional investigative tactics fail to yield a solid suspect.” Familial DNA searches have indeed helped nab people who might otherwise have evaded justice. In the most celebrated example, Los Angeles police arrested a man believed to be the Grim Sleeper serial killer after discovering that the crime scene DNA shared a significant number of genetic markers with that of a convicted felon—who turned out to be the man’s son.
But the well-publicized success stories obscure the fact that familial DNA searches can generate more noise than signal. “Anyone who knows the science understands that there’s a high rate of false positives,” says Erin Murphy, a New York University law professor and the author of Inside the Cell: The Dark Side of Forensic DNA.