personality. >> the medical examiner ruled hannah's death a homicide by asphyxiation, saying she was strangled to death. but little else was clear. for instance, they found semen inside the body during the autopsy, but said it wasn't worth anything because it had degraded in the week she was in the car. police never checked brad oborn's alibi the night she disappeared, never checked paper records, and never checked the carpet inside denny's apartment. >> they can spray a chemical on this alleged evidence and it can be tested. that was never done. >> visible blood spots were found on denny's apartment walls, but in the percent sent out for testing, none came back for hannah. >> no dna, no blood. you theorize she was killed there, but yet there's no trace of her. >> yep.