As the investigation into Nancy Guthrie’s disappearance continues with no suspect publicly identified and challenges with DNA evidence, experts may turn to digital forensics. Authorities have said little about digital evidence in the case, but one leading expert has no doubt that whoever is responsible for the 84-year-old’s disappearance left a digital trail. “People forget how much their data spreads across devices. So the same thing that makes investigations hard make it hard for criminals to clean up,” said Heather Barnhart, a digital forensics expert with the SANS Institute and Cellebrite. Barnhart helped investigate the University of Idaho murders, for which Bryan Kohberger was sentenced to four life sentences. Barnhart is not involved in the Guthrie investigation. “Your phone is the silent witness to your life. It knows everything you do,” Barnhart said.…