Familial DNA searching has massive false positives, but is being used to tag suspects:
The bewildered Usry soon learned that he was a suspect in the 1996 murder of an Idaho Falls teenager named Angie Dodge. Though a man had been convicted of that crime after giving an iffy confession, his DNA didn’t match what was found at the crime scene. Detectives had focused on Usry after running a familial DNA search, a technique that allows investigators to identify suspects who don’t have DNA in a law enforcement database but whose close relatives have had their genetic profiles cataloged. In Usry’s case the crime scene DNA bore numerous similarities to that of Usry’s father, who years earlier had donated a DNA sample to a genealogy project through his Mormon church in Mississippi. That project’s database was later purchased by Ancestry, which made it publicly searchable—a decision that didn’t take into account the possibility that cops might someday use it to hunt for genetic leads. Usry, whose story was first reported in The New Orleans Advocate, was finally cleared after a nerve-racking 33-day wait — the DNA extracted from his cheek cells didn’t match that of Dodge’s killer, whom detectives still seek. But the fact that he fell under suspicion in the first place is the latest sign that it’s time to set ground rules for familial DNA searching, before misuse of the imperfect technology starts ruining lives.