attack, why was no blood evidence ever found on david dooley? and why wasn't any of the dna found at the scene a match to his? the prosecutor argued the janitor worked every day with cleaning supplies and plastic bags. together, perfect for removing evidence of a crime. >> at the time david dooley attacked michelle in that hallway, what did he have with him? a rolling crime scene clean-up cart with a trash bag in the middle of it. >> it's my personal belief that when he left that building, he took with him a bag containing all of the evidence that was missing from the scene. >> reporter: a cover-up so spotless, only a janitor could manage it, said the prosecutor. it was only his story, she said, that was a mess. >> it's very hard for a person to explain how they can't tell the same story twice, and in these circumstances we had four separate statements from him. >> reporter: detective mcvay testified it was only in dooley's second interview at his apartment that dooley first