RALEIGH, N.C. — New allegations have surfaced in a murder case that gripped the entire country.

The case involves a former Fort Bragg Green Beret who was convicted of murdering his wife and two children at Fort Bragg.

After 26 years, Jeffrey MacDonald still insists he didn't kill his family.

But, Tuesday there was a new appeal and allegations of witness tampering by the lead prosecutor.

In an exclusive interview Wednesday, the former prosecutor, Jim Blackburn, told WRAL that the charges are totally untrue and without merit.

More than 1,000 pages of documents were filed Tuesday with the 4th Circuit Court of Appeals in Richmond that included allegations of "government misconduct" resulting in what the attorneys describe as a clear "constitutional violation."

MacDonald's lawyers claim a key defense witness, Helena Stoeckley, was intimidated by lead prosecutor Jim Blackburn.

Blackburn said he's shocked.

"This motion is just not maybe not true, it's totally not true," Blackburn said.

The allegations are based on the statements of a now retired deputy, U.S. Marshal Jim Britt.

Stoeckley was one of the people MacDonald claimed broke into his home and killed his family.

Standard procedure is for both sides to talk with the witness before testimony. There is no dispute over if both sides interviewed Stoeckley.

There is a dispute over the allegation that "Blackburn invited Britt into his office to be a witness to the interview."

"It makes no logical sense for us to invite an outside person into a confidential meeting like this," Blackburn said.

Britt will not talk about the case until the appeal is resolved.

However, in the documents filed Tuesday, Britt claims Stoeckley was intimidated by Blackburn.

Britt said that during the interview, Blackburn told the witness if she testified she was in MacDonald's home the night of the killings, he would indict her for murder.

The next day, McDonald's attorneys claim, Blackburn used "leading questions" that forced Stoeckley to testify "she knew nothing of the murders."

"His story never happened," Blackburn said. "I never threatened Helena ... tampered with her at all."

Blackburn also told WRAL he understood why he's at the center of this storm.

After leaving the U.S. Attorney's Office, while in private practice, he embezzled from clients, served jail time and lost his law license.

He said he knows his credibility is on the line.

Helena Stoeckley, the witness who could help clear the air, died in 1980.