Article continues below advertisementForensic experts are combing through digital footprints and DNA evidence in a desperate effort to identify a suspect in the disappearance of Nancy Guthrie, the 84-year-old mother of Today show host Savannah Guthrie.Digital forensics expert Heather Barnhart - a senior director at Cellebrite and an instructor at the SANS Institute who assisted in the Bryan Kohberger case in Idaho - has emphasized that "the loudest evidence can be the lack of evidence.