Up next a chance encounter results in a vicious murder.

The first people to arrive discovered a very brutal scene.

There was a lot of blood.

And a lot of suspects.

We're talking in years of work.

We eliminated over 400 people.

Investigators carry on despite setback after setback.

While this case may have grown cold, it was never closed.

Then forensic science from an unrelated crime helps expose a killer.

For whatever reason, this case just draws you in and you want to be a part of it. Wisconsin. Wisconsin is one of the Great Lake States notorious for brutal winters.

But for reasons no one could later explain, on a December night in 1984,

a young woman decided to brave the bitter weather and walk home.

It was snowing and it was cold. She had to walk a number of miles to her

home. A few hours later a man went out to get his newspaper and came upon a shocking sight.

The body was discovered along a gravel driveway. It was a female. She was laying on her back. She was naked from the

breast down. Her head was bloodied. It was evident that she had been bludgeoned on the right side of her head.

Even veteran detectives were stunned by this level of violence.

The victim had been struck with such force that cast off blood spatter, which flies off a weapon during repeated strikes, had traveled all the way up into the surrounding trees. She had been violently strangled. the The rage and how violent the scene was really was disturbing.

The murder weapon was not at the scene.

Blood evidence made it clear the victim had been killed where she was found. Since she wasn't

frozen and temperatures were frigid, police knew she hadn't been there long.

She was identified as 18-year-old Tracy Hammerberg.

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