Jeffrey MacDonald, a clean-cut Green Beret and doctor convicted of killing of his pregnant wife and their two daughters, is getting another chance to try proving his innocence — more than four decades after the nation was gripped by his tales of Charles Manson-like hippies doped up on acid slaughtering his family.

The case now hinges on something that wasn't available when he was first put on trial: DNA evidence. A federal judge planned to hold a hearing Monday to consider new DNA evidence and witness testimony that MacDonald and his supporters say will finally clear him of a crime that became the basis of Joe McGinniss' best-selling book "Fatal Vision" and a made-for-TV drama.

It's the latest twist in a case that has been the subject of military and civilian courts, intense legal wrangling and shifting alliances.