the first week of the investigation about a green van where a man would get out and go into the woods behind the house. >> which is where they found the bandanna. he was casing the house. before the murder. that was in their file. in 1987. they knew. >> once we got the dna results, i mean, "a," it was christine morton's blood, and "b," that it wasn't michael's blood or skin cells, i should say, on the bandanna. none of his dna. you know, that was terrific. >> the dna of this other person was intermingled with christine's dna. it really places the bandanna at the murder scene. >> so the next step was to work with the texas state crime lab to get it entered into the database to see if it matched any convicted offenders or unsolved crimes.