Your DNA Test Could Send a Relative to Jail

On any given day, CeCe Moore’s inbox is flooded with strangers asking her to solve the mysteries of life and death, and on a good day, she can. Over the past year, working from anonymous DNA samples, Moore helped identify the suspect in a murder by tracking old migration patterns from Poland to northern New Jersey; solved an assault case in which female DNA at the crime scene turned out to have been left not by the usual sort of explicable coincidence but by an actual female perpetrator; and made a key discovery in a murder investigation when the gravestone of an apparently childless woman was found to bear the inscription “MOTHER.” Some of these she knocked out in a few frenzied days. But there was also one cold case that had dogged her for close to two and a half years: the murder, in Gresham, Ore., of a woman named Barbara Tucker.

Moore is perhaps the most prominent figure in the field of genetic genealogy — the mapping and measuring of how relatives share DNA — which was developed...