"I had no knowledge of it," said Sissy Atkinson in an interview with Dateline NBC. "I was not there. I had no participation in it."

Sissy Atkinson is now 52 years old. She admits she’s an addict: cocaine, meth, painkillers.

And she was, perhaps understandably, not entirely happy about still facing questions from us, or Centurion, about this murder nearly three decades ago.

Sissy Atkinson: I told those ministry guys, I said when we all die and go to heaven and you guys find out that I had no knowledge of it, I was not there. I had no participation in it. I don't know who did it. I hope you guys will be gentlemen enough to come and find me in heaven and tell me you're sorry.

In fact, said Sissy, on the night of the murder she was indeed with that group of girls, the subjects of the rumor.

But she said that after buying beer for some underage teens at a local bar and the police coming by, she made a request to one of the girls.

Sissy Atkinson: So I said, “Could you please take me home, I don't want to be caught for contributing.” She drove me to my home and I went to bed.

Keith Morrison: So you were in bed that night by when? Do you remember?

Sissy Atkinson: Oh, 11.

Keith Morrison: Eleven o'clock at night?

Sissy Atkinson: Yes.

Keith Morrison: Who can back up that alibi?

Sissy Atkinson: Well, nobody. My mom's not here no more. And I lived with my mom. Just me and my mom and my baby.

Keith Morrison: But she's the only one who could back up your alibi? And she's gone?

Sissy Atkinson: Yes.

Keith Morrison: You know, we've heard from maybe, I don't know, a half-dozen people who put you there that night.

Sissy Atkinson: No.

Keith Morrison: Not possible?

Sissy Atkinson: Not possible whatsoever. It would make me go crazy if I knew that.

Keith Morrison: Well that's the allegation. That it kind of did over the years. It may be the reason that you've had trouble with drugs is because…

Sissy Atkinson: Oh no, there's different reasons.

Keith Morrison: Why would we have witnesses who say that you said a few years after the murder that you got away with the perfect crime?

Sissy Atkinson: No, and that never ever came out of my mouth. Never.

But what would Sissy Atkinson say when she learned that one of her accusers was her own flesh and blood?

Keith Morrison: Why would your own brother say that you started to tell him about how you were involved in that?

Sissy Atkinson: What brother?

Keith Morrison: J.D.

Sissy Atkinson: J.D.? Oh, no. I don't even know what he's talking about. I’ve never talked to him about that. Ever.

Well, as you've seen, that's not what J.D. Atkinson told us during our interview at the Montana State Prison. So, we played the interview for his sister.

Sissy Atkinson: J.D.! I’m really going to confront him on this because he's tripping.

Keith Morrison: Is it possible that it's blocked somehow…

Sissy Atkinson: No. I 've got a very, very good memory.

Keith Morrison: And I don't want to be cruel when I say this, but if you do have a really good memory, you're probably the only addict on the face of the earth that does. What is it going to take to stop the whispers?

Sissy Atkinson: I don't know, I don't care. Because I’m not involved. Let them talk all they want.

And in fact, there is no physical evidence linking Sissy Atkinson to the crime scene. That bloody palm print? Not hers. No fingerprints, either.

Sissy Atkinson: I have been cleared of everything. Hand print. Everything. If I would've been down there I’m sure they would have found some kind of DNA on me. You know? Something?

After our interview with Sissy, we went looking for more of those girls, now women, whom witnesses have placed at the scene. Another name that comes up again and again is Maude Greyhawk. Her father was the police officer who kicked in the door to the evidence room the night after the murder. We repeatedly tried to reach her, but could not.

And a third name is Joanne Jackson. Like Sissy, Joanne claims to have been home in bed hours before the murder.

Jackson: I don't have any reason to be implicated in this whatsoever. I went home, I talked to my mother around 11 o'clock.

Keith Morrison: And after that you have no idea what happened.

Jackson: No.

Keith Morrison: You were asleep the rest of the time?

Jackson: Yes..

Joanne Jackson’s fingerprints and palm prints have also been compared to those left at the scene. No match. Yet Centurion says there are several others, at least four women and two men, who might have been there but their prints have never been compared.

Keith Morrison: A lot of kids were home by 11 o'clock that night, it turns out.

Jackson: I don't know why. I just don't understand it. Because my sister was with me, that's the weird thing. You know they must have questioned her 10,000 times and she said the same thing.

So where does all this leave Barry Beach? What is the truth?

Well, Centurion's investigation would soon lead to something Beach had been seeking for decades: a remarkable hearing, unlike any ever held before in the state of Montana, maybe in all the United States. It was a new trial, of sorts, and a shot at freedom.

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