It's usually easy to determine how a criminal entered the crime scene. But in this case, it was far from clear. It looked like the killer vanished into thin air...and perhaps he had.

When a young fireman died from what appeared to be serious but undiagnosed heart disease, his family and friends were devastated but they had no proof of foul play. Then they learned that, six years earlier in a nearby town, a young police officer died in the same way. The men had one thing in common: at the time of their deaths, they were married to the same woman.

How unlucky could one man be? His wife had taken her own life, and his college sweetheart had killed herself in much the same fashion fourteen years earlier. Investigators had to determine if this was a bizarre coincidence, or an attempt to get away with murder... twice.

A woman was brutally murdered in her home, and the only witnesses to the crime were the family dogs. An expert in canine behavior was convinced the killer knew both the victim and the animals, and he was determined find out exactly what the dogs had seen.

After the suspect was convicted of arson and murder, he steadfastly maintained he did not commit the crimes, but he was sentenced to a minimum of 25 years in prison. He had no money, no lawyer and only a fifth grade education, but he never gave up. He turned to the law books in the prison library and television programs about forensic science, and set out to prove his innocence. [also marked as S12:25]