Forensic Files - Season 2 Episode 10 -

For more than a year, angry, hateful letters were sent to a first grade school teacher in a small town in Pennsylvania. When scientists analyzed the letters, they found evidence that the stalker knew a lot about the victim - more, in fact, than anyone could possibly have imagined. DNA analysis would eventually help seal the perpetrator's fate. Medical Detectives, Season 2, Ep 10.