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Familial DNA Testing Nabs Alleged Serial Killer
cremeglace writes "A quarter-century of conventional detective work failed to track down the killer responsible for the deaths of at least 10 young women in south Los Angeles dating back to the mid-1980s. But a discarded piece of pizza and a relatively new method of DNA testing has finally cracked the case, police announced last week. On July 7, L.A. police arrested Lonnie Franklin Jr., 57, a former garage attendant and sanitation worker they suspect is the serial killer nicknamed the 'Grim Sleeper.' The key evidence? A match between crime-scene DNA and the suspect's son, obtained by a search through the state's data bank of DNA collected from 1.3 million convicted felons."
Familial searches from a DNA database the size of the one in California are very, very likely to produce false positives. For example, a study of the Arizona CODIS database carried out in 2005 showed that approximately 1 in every 228 profiles in the database matched another profile in the database at nine or more loci, that approximately 1 in every 1,489 profiles matched at 10 loci, 1 in 16,374 profiles matched at 11 loci, and 1 in 32,747 matched at 12 loci. http://www.maa.org/devlin/devlin_10_06.html
With California currently having the third largest DNA database in the world, the odds of ANY new genetic evidence matching on a cold search is way too likely.