Article continues below advertisementThe ongoing search for Nancy Guthrie has drawn attention to the critical issue of proof of life, as experts weigh in on the implications for her case. Nancy, 84, was reported missing from her home in Tucson, Ariz., on February 1. The search has intensified following a ransom demand of $6 million, with a deadline set for February 9.Article continues below advertisementSource: NBCExperts stressed the need for proof of life in Nancy Guthrie's kidnapping case.