I'm Dr. Layne McDonald, and today I need to walk you through a developing story that's raising important questions about both public safety and digital privacy. The FBI has released surveillance footage in the disappearance of Nancy Guthrie, an 84-year-old Tucson woman who also happens to be the mother of NBC "Today" host Savannah Guthrie. What makes this case particularly complex is how investigators obtained the footage, and what it reveals about the intersection of doorbel
