RALEIGH, N.C. >> 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.

“This is Jeff’s opportunity to be back in court almost 33 years to the day of his conviction,” said Kathryn MacDonald, who married him a decade ago while he has been in prison.

MacDonald, now 68 and not eligible for parole until 2020, has never wavered from his claim that he didn’t kill his pregnant wife, Colette, and their two daughters, 5-year-old Kimberley and 2-year-old Kristen. He has maintained that he awoke on their sofa in their home at Fort Bragg in the early morning hours of Feb. 17, 1970, as they were being attacked by three men and a woman.

In an October 2000 letter MacDonald wrote to Kathryn MacDonald, provided by her to The Associated Press, he wrote: “It would be a dishonor to their memory to compromise the truth and ‘admit’ to something I didn’t do — no matter how long it takes.”

The gruesome stabbing and beating deaths came just three months after the Manson Family slayings in California were revealed. The pregnant wife and MacDonald’s description of the woman attacker chanting “acid is groovy, kill the pigs” all fed into fears that Manson-type killers were on the loose in North Carolina. The word “pig” was written in blood on a headboard — the same word that was written on the door of pregnant Manson victim Sharon Tate’s house in Los Angeles.

The Army charged the Ivy League-educated MacDonald with murder, then dropped the charges months later after an Article 32 hearing. By December 1970, MacDonald was not just a free man but also had received an honorable discharge.

But his father-in-law, Alfred Kassab, who initially believed in his innocence, changed his mind and eventually persuaded prosecutors to pursue the case in civilian court. In 1979, MacDonald was charged, convicted and sentenced to life in prison, a sentence he now serves at the federal prison in Cumberland, Md.

MacDonald has stood by his innocence claim so strongly that he refused to apply for parole for years, and when he did, he refused to acknowledge any guilt and was rejected. MacDonald and his supporters have continued to pursue legal avenues over the years to try to clear his name.

U.S. District Court Judge James Fox will consider two types of evidence: three hairs that don’t match the family’s DNA and a statement from Jimmy Britt, a deputy U.S. marshal when the case was tried. Britt, who has since died, gave a statement to defense attorneys in 2005 that he heard prosecutor Jim Blackburn threaten Helena Stoeckley, a troubled local woman whom MacDonald had identified as one of the attackers.

A previous MacDonald attorney has said Stoeckley was prepared to testify she was in the MacDonald home the night of the murders until Blackburn threatened to charge her with the slayings. She later testified she couldn’t remember where she was that night.

The 4th U.S. Circuit Court of Appeals granted MacDonald’s request for the hearing. It’s expected to last up to two weeks, and Fox will determine whether to order a new trial.

“This is the first time the judge is having to consider all the evidence in the case as a whole,” said Chris Mumma, head of the N.C. Center on Actual Innocence, which has a pending request for DNA testing on other items found in the home. “Pieces of evidence were considered in the past. Now the 4th Circuit has told the judge to consider the evidence as a whole, whether admitted at trial or not.”

A lab was able to get DNA testing from the roots of hair, so Mumma is optimistic that other evidence can be tested if the judge agreed. The center has asked that 40 items be tested. Hundreds of bloodstains were collected, along with the weapons, the eyeglasses the children wore and pieces of the gloves used to write the word “pig.”

In 1979, only blood typing existed, not DNA testing. Jeffrey, Colette and their daughters all had different blood types, so prosecutors could recreate which people were in which rooms together.

But, Mumma asks, what if the blood types belonged to people outside the MacDonald home?

“There’s evidence that I think would be worth testing to determine if there’s DNA evidence not tied to family members — or that does,” she said. “The DNA testing may completely confirm the government’s theory.”

Fox will consider the statement of Britt, who accused former prosecutor Jim Blackburn of threatening Stoeckley. Blackburn later went into private practice and was found guilty of several ethical violations. He was disbarred and served a prison sentence. Because he’s a likely witness, Blackburn can’t talk about the case. He does, however, support the trial verdict. “We prosecuted the case to the best of our ability,” he said. “We still believe the verdict was correct.”

Like the Manson murders, the MacDonald killings led to books, most famously “Fatal Vision,” which also was the basis of a television miniseries that concluded MacDonald was guilty. Earlier this month, documentary filmmaker Errol Morris’ book, “A Wilderness of Error,” was published. Morris concluded that MacDonald did not get a fair trial and might not be guilty.

There will be some familiar faces at the proceedings. But others who have played central roles in the case will be missing: Stoeckley died in 1983 at age 32 of pneumonia and cirrhosis of the liver; Britt, the U.S. deputy marshal who said the prosecutor threatened Stoeckley, also has since died. Jeffrey MacDonald’s father-in-law, Kassab, also has died.

Now Colette MacDonald’s brother, Bob Stevenson, will be there to fill his role

“The truth is, there is nothing new out there,” said Stevenson, 73, who declined to say where he lives, saying he receives death threats. “There is nothing. Do you know how much DNA is in my home and your home? The mere discovery of DNA has nothing to do with a man’s guilt.”

Stevenson said he promised Kassab before he died in 1994 that he would continue to pursue MacDonald.

“Until he is dead or I am dead, we will be battling as adversaries,” he said, adding later: “I will never lose interest. I will never lose zeal. I will never lose faith.”