when you turned out the lights, you sprayed everything with luminol, what did you see here?t right in here, there was actually the silhouette of a human body as if someone had slumped. you could see the head, the shoulders, you could see the hips and the knees. and then right here in this >> reporter: did that affect you, seeing that silhouette of a body slumped against the wall here? >> it was shocking. i think what affected me even more than seeing it was the reaction of seasoned detectives that were in the room. they were shocked as well. >> reporter: and by thursday, cops still haven't found shelby, but they sure have more questions for michael wilkie. >> he had done something with her. and our goal at that point was to try to figure out exactly what he did. >> reporter: when we come back -- >> i don't know. i honestly don't know. >> reporter: michael wilkie in the box. turning on the waterworks once again. >> i didn't kill her. >> reporter: and -- is another suspect about to emerge? >> he came over there and he told me if i told anybody about that he would kill me. >> r

finally, investigators sprayed the inside of persitz's car with luminol.vealed evidence of a gunshot. >> it looked like stars. there were hundreds of spots on the roof of the headliner of the car, which would have been consistent with the high-velocity mist if someone gets shot in the head. >> this indicated that michael was sitting in the driver's seat of persitz's car when he was killed. [ gunshot ] investigators found a receipt in persitz's office for a pair of handcuffs that could have been used in the abduction. zachary persitz was arrested and charged with first-degree murder. even his lawyer acknowledged the strength of the prosecution's case. >> trying this case was like being a human punching bag. and then i saw him, slowly coming down the aisle. one of those guys who just can't stop talking. i was downloading a movie. i was trying to download a movie. i have verizon. i don't. i get that little spinning wheel. download didn't finish. i finished the download. headphones on. and i'm safe. i didn't finish in time. so. many. stories. vo: join us and s

they even sprayed his truck with luminol looking for signs of blood. >> we took the seats out, we did. and there was nothing. >> reporter: police briefly detained sam, but he was back home by morning. now daron wyatt focused on xavier. >> and we really approached it very low key. "we think that you can really provide some great information for us. would you mind coming down with us and talking." >> reporter: they brought him down to the station and listened patiently as he distanced himself from cathy torrez. >> he'd never been shopping with her, never changed a tire on her car, never carried groceries. we went through the whole litany of things that -- >> reporter: and he's all, "oh no, no, that's --" >> would -- >> reporter: that's all true. "i'm a million miles away from her"? >> right, right separated himself. >> reporter: but in so doing, xavier ruled out any innocent explanation for finding his dna and fingerprint on her car. so when police told him that's exactly what they had found -- >> it was like vapor lock. and then all of a sudden he said, "well, you know, this one time i