This is an ABC podcast.

If you're an Aboriginal or Torres Strait Islander person, we want you to know that this series contains a name of someone who has died.

One of Mark's closest friends, Jason Wan, is halfway through an interview with me at a hotel in Tamworth.

He's just given me the biggest lead in my five-year investigation.

And if it's true, this lead could solve the case.

She said, look, I've had to come around and see you guys. I've just told me something and it's really concerned me and I need to tell you.

It's a story that comes from someone he trusts completely.

She said that got drunk, had become very emotional and had told her that he was there the night that Mark was dead

and that he'd placed Mark's body on the tracks.

So Greg allegedly confessed years ago to putting Mark's body on the tracks.

He was Mark's friend.

He was out with Mark that night at Dominoes. We're

beeping out Greg's real name. Jason has another story about him from the day of Mark's funeral.

Um, mum gave us a yellow rose each to place down Mark's grave. And I remember that that...

...was quite hesitant to do that for some reason, whatever he had his own reasons.

And on the way home from the funeral, we had to stop the car.

Sitting in the back, he became quite nauseous and actually vomited on the way home from the funeral.

People experience grief in different ways, so that doesn't really amount to anything.

Maybe Greg really was sick, or his reaction to grief was a physical one.

But what I can't get past is this allegation that Greg confessed to putting Mark's body on the tracks.

So I asked Jason again, what exactly is Greg supposed to have said?

Basically he said that he was there that night, the night that Mark was killed, and that he had put his

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