>> the doctor who performed the autopsy was not a forensic pathologist, but he did something virtually unheard of at the time. for reasons not entirely clear, he kept a vial of donna's blood in refrigerated storage, and two years after her death, it was sent to the forensic lab for testing. a sample was placed in a gas chromatograph mass spectrometer. which broke the blood down into its chemical components. traces of a common antidepressant known as elavil were clearly present in donna's blood. >> in someone who had never taken the drug before, i believe even one pill could cause them to be very drowsy, dizzy, possibly disoriented. >> but how did elavil get into her system? >> the presence of elavil in the victim's body was crucial because she had no prescription for it.