The files examined by prosecutors on Friday raised further questions about why Mr Powell was never charged in her disappearance despite her blood being found in their home in Utah.
Her father Chuck Cox said that had teh police acted before he started the gas-fueled inferno in Washington state earlier this year, his two young grandsons would not have been killed.
'When I heard them [the new evidence], it was like, well, why didn't you arrest him already?' Mr Cox told ABC News. 'Had he been to jail, my grandchildren would still be alive.'
He said that he had wanted to protect his grandchildren, but now he just wants to find his daughter.
'We let the police do their investigation and hope that sometime we'll be able to talk to Steve Powell (her father-in-law) and he'll be able to tell her where she is if he knows.'
Investigators in West Valley City, Utah, never arrested Josh Powell or even publicly labeled him as a suspect in his wife's disappearance. Read More