Dr. Tracey Corey: We're there to try to answer the questions of "How did this person die? When did this person die? What was happening during the death?"

As the investigation into the slain couple in the car continues, another strange story about a killing and a buried body is playing out 50 miles away, in rural Hardin County, Ky.

It's a case in which Dr. Corey's office will take on a unique role, helping police verify if a confessed killer is telling the truth.

Victoria Corderi: How unusual is that?
Dr. Tracey Corey: I'd say that's not common. That that's a pretty rare event.

It all began in late January, when a 29-year-old fast food employee named Roy Jeffries disappeared, leaving in his wake two frantic parents and many unanswered questions.

Margaret Brown: Did somebody beat him up? Or hit him with a car? And he's laying out. And it's freezing. And he's going to die from exposure.

Desperate, they distributed fliers and scoured the area, including the dumpsters.

Charles: I thought, man, I don't want to find no bodies in this thing. That's the last thing I want to find.

Margaret Brown: We've looked until the police said "You've got to stop. Quit knocking on doors." You know, "Quit going places. We don't know what's happened here. Could be dangerous. We'll be looking for you next."

Monday, Feb. 5, Kentucky State Police Post
After days of more searching, there's a possible break in the case. Police get a tip. It's a call from a man who says he knows what happened to Roy Jeffries because, he says, he killed him.

Detective: How many times did you shoot?
Suspect: I only shot him once.

The man, 20-year-old Clayton Kerr, tells police that he will take them to where he has hidden the body. But only if the prosecutor, Chris Shaw, first agrees to a deal. Kerr would plead to manslaughter instead of facing a murder charge.

Prosecutor Shaw: Since my time in this office, as well as working as a practicing lawyer around this county, I've not seen one like it. We were being approached before there technically was a case.

The prosecutor wants to take the deal, but first he wanted to run it by Jeffries' parents.

Prosecutor Shaw: We knew we had a family out there who was missing their family member, that there was a body out there that we needed to try to recover.

As part of the deal Kerr would receive a 20 year sentence, of which he must serve 17 1/2 years. Reluctantly, Roy Jeffries' parents agree.

Charles: This is our best chance, you know.
Margaret Brown: And it's a hard decision.
Charles: And it is. 17 1/2 years isn't much for killing somebody.

So, with his attorney at his side, Clayton Kerr confesses to the killing, chapter and verse, to a homicide detective who is off-camera.

Detective Jason Propes: Did you kill Roy Marshall Jeffries?
Kerr: Yes, I did.
Detective: OK. And do you know where his body is located?
Kerr: Yes, I do.
Detective: OK, and where is that at?
Kerr: It's in the woods behind my mother and father's home.

Kerr tells police that his girlfriend worked with Jeffries at this fast food restaurant and that Jeffries made no secret of his desires.

Kerr: In the past he had made moves towards my fiancée … And it was openly in front of my face.
Detective: So he had -- he had flirted with her? Is that what we would call it?
Kerr: Yeah. He tried to hit on her.

On the day of the murder, Kerr says, he lured Jeffries into the woods near his house and his impulses suddenly took over. He pulled out a .22-caliber gun he'd taken from his parents' home.

Detective: What happened next?
Kerr: I just snapped and pulled out the gun … I looked away and I shot.
I just shot like this … And then as soon as he went down, I started throwing brush on him. And then I took off.

Later, he says, he returned to the woods to get rid of the gun and to dig a grave for Jeffries.

Kerr: I dug a hole and I threw him down in it.

Tuesday, Feb. 6: Kerr family farm
Kerr confessed, but now it's time to prove he was telling the truth.

Kerr is leading police into the woods behind his family's farm to where he claims he buried Roy Jeffries. Hardin County coroner Bill Lee is on hand to help the police.

Bill Lee: Twenty years as coroner, first time I had to uncover a buried body.

Coroner Lee will take charge of the body -- if they find one. Police at the scene wonder if Kerr may have made up the whole story.

Meanwhile, the missing man's parents have been told about the killer's confession. They are distraught, imagining how their son may have suffered.

Margaret Brown: I think that would be the worst thing in the world to know that you are going to your death. You're going to go to be executed. I just can't imagine that kind of fear.

Two hours have passed since Kerr led police deep into the woods. Suddenly, he appears -- and he's ushered off the property, cloaking his face from the cameras, handcuffed and clinging to a bible as he's placed in a police cruiser and taken to jail.

Now, it's up to coroner Lee, his deputy and two detectives to see if Kerr was telling the truth.

Back in the woods, the tranquil sounds of nature seem out of sync with the off-key clank of shovels hitting the frozen ground.

Our video camera was not allowed on the property to shoot in the woods, so it's police photographs of the excavation that you're seeing. But our microphone is capturing the real sounds of the digging as it's happening.

Bill Lee: The first inch or so of the covering was fairly hard.

Police make an important discovery: a .22-caliber gun hidden under the leaves.

After more digging, searchers uncover a sneaker.

Bill Lee: The shoe was off. There was a white sock.

Then some clothing...

Bill Lee: Here's a hand.

And, finally, they find a body. It's Roy Jeffries' body.

Bill Lee: He was face down. And the first thing that showed on the back was a University of Michigan jacket.

According to Kerr's confession, that jacket is what made him snap on the day of the murder.

(confession tape)
Kerr: He was wearing the same clothes he was wearing whenever he made those comments.

They were the same clothes Jeffries had worn weeks before when he'd supposedly flirted with Kerr's girlfriend.

Bill Lee: And we're just careful going around the perimeter not to disturb the body itself.

So why more than a week after the murder did Kerr come forward? Because, he told police in his videotaped confession, he was so overwhelmed with guilt he went to his church minister.

Detective: Did you tell him what you'd done?
Kerr: Yeah. I was a bad man. And I needed to pay for what I'd done.
Detective: Did you tell him what you'd done?
Clayton Kerr: Yeah. I was a bad man. And I needed to pay for what I'd done.

So far, the evidence on the scene suggests Kerr is telling the truth, but key forensic questions remain unanswered.

Shaw: So we were concerned to know from medical examiner was there any sign of whether he would have still been breathing at the time he was put in the ground.

It's a key issue, because if he buried Jeffries alive, Kerr's deal with the prosecutor would be null and void.

Charles: But if he lies, they said, then we just throw it all out. And we still got all the evidence.

Forensic science will serve as the lie detector for other questions as well: the number of gunshots, and whether Kerr fired from behind without even looking as he'd demonstrated in his confession.

For Dr. Corey's office it will be a rush to answer questions, solve a crime and determine punishment all at once. But first, coroner Bill Lee gets a phone call from the county dispatcher.

Coroner Bill Lee: Oh, god. Nelson county? Oh, my gosh … Eight people burned up in a house fire. Man, gosh.

It's the nature of the business, working on one death and getting news of another. This time, it's a massive tragedy -- a house fire -- that would send Dr. Corey's office into overdrive.

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