Nancy Guthrie investigators turn to genetic genealogy. It's worked in big cases before.

Investigators in the Nancy Guthrie case in Arizona have turned to genetic genealogy as they try to make the most of DNA evidence collected during the search for the 84-year-old mother of 'Today' show co-host Savannah Guthrie, who was believed to have been forcibly taken from her Tucson home in the middle of the night nearly three weeks ago. The Pima County Sheriff's Department announced this week that Savannah Guthrie, her two siblings and their spouses have been cleared as suspects in the disappearance case. The department revealed that a DNA profile from a set of gloves found about 2 miles from Nancy Guthrie's house didn't match any entries in the national FBI Combined DNA Index System (CODIS), nor did it match other DNA evidence collected from the property. Genetic genealogy has emerged as a promising investigative technique that has cracked several notable cases in the past decade. Emanuel Katranakis, a former deputy chief with the New York Police Department, explained that genetic genealogy is essentially the final effort to match a DNA sample to a person when traditional database searches yield no results. 'If this perpetrator has a relative that is a convicted offender in the database, you build a family tree around it,' Katranakis said. This strategy proved successful in the Idaho case where Bryan Kohberger was identified as the killer of four college students after investigators used genealogy sites to build family trees using crime scene DNA. Similarly, the technique helped identify the Golden State Killer in California after decades of investigation. The use of genetic genealogy requires sufficient DNA samples for additional analysis, according to Suzanna Ryan, laboratory director at Pure Gold Forensics. She noted that ideal samples would have a single source profile, like blood or semen, but labs can also work with mixtures where the potential perpetrator's DNA constitutes the majority component. While FamilyTreeDNA stated it doesn't work directly with law enforcement on forensic genetic genealogy cases, related work is carried out through an independent third-party partner that uses a consent-based database. The company emphasized that participation in investigative genetic genealogy matching is strictly voluntary and opt-in only, with customer privacy and data security as top priorities.