mr. radder's body and manipulated the area to make it look like mr. sustained the shot and fell backwards. >> the expert demonstrated for the jury how after lee was shot, his body would have slumped forward in the chair, not backward, the way he was found. so rob must have moved lee's body on to the ground. which, accounts, said the experts for the blood droppings on the floor. >> i think he just dragged him on to the ground. >> narrator: so the forensics said murder. but why would he do it? what possible motivation did he have? no idea, said the prosecutor. >> there's no evidence of a disagreement between the two of them, nothing like that? >> no. >> narrator: but that wasn't the issue, he said. hard evidence was -- >> when you start putting all the pieces together, you only get one explanation and that's murder. >> narrator: and that wasn't quite true. there was a second explanation. the jury was about to hear it. >> reporter: coming un, the defense presents it's own scientific evidence, arguing there's no way rob fisher could have been lee's killer.