After 50 days, legendary cold-case detective dives into the Nancy Guthrie case — including the most crucial evidence

As the search for Nancy Guthrie hit its 50th day Sunday, leaving the local sheriff desperate and humiliated, a legendary cold-case detective insisted to The Post that the case is still ripe with potential leads. “Nancy’s case is still very fresh,” said Brian Martin, the crack detective from Fort Payne, Ind., who helped catch the killer of 8-year-old April Tinsley almost 30 years after her murder. Martin said he is optimistic that law enforcement will track down the abductor of the 84-year-old mom of “Today” show host Savannah Guthrie, after Nancy vanished with nary a trace from her home near...