Article continues below advertisementAs the case of missing Nancy Guthrie, the 84-year-old mother of Today show co-host Savannah Guthrie, continues to baffle investigators, true crime podcaster Nancy Grace dnd forensic experts have zeroed in on specific physical evidence at the Guthrie home that resembles a trail or "track-like" markings.After showing photos of what appear to be a trail or track marks of some sort observed in the driveway near a rocky area close to Nancy's Tucson, Ariz.