Lesley Stahl kicks off her new role tonight as anchor of '48 Hours' with a fresh look at the Jon Benet Ramsey case.She has the first interview with Patsy Ramsey since the latter was diagnosed with a recurrence of ovarian cancer..Shows never before seen tapes of police interrogations..Boasts an exclusive with Lou Smit, one of the original investigators of the Boulder, Colorado case.. (he thinks the Ramseys are innocent)And there is new evidence, including fiber presence linked to one of the parents.The local police department offers its relevations and private views of the Ramseys as potential suspects.