by chanin's killer.his time you believed she was dead? >> right. based on the 911 call, we believe she's deceased and yet someone is using her cellphone to communicate. >> reporter: and to prove it must have been clay who sent those messages, they entered into evidence this seemingly innocuous text message from around 3:00 p.m. that afternoon. >> at 3:06 p.m. chanin starbuck phone to logan starbuck phone, send marsh a note, dad will be there in ten minutes. >> reporter: send marsh a note? who besides his mother might know the nickname marsh? the youngest starbuck marshall came to the stand. >> how often would your dad call you marsh? >> a lot. he also called me son and marshall. >> but he did call you marsh a lot? >> mm-hmm. >> reporter: yes, it had been an intimate act, an angry ex-husband killing the mother of his children, then staging the scene as a humiliating sex crime, premeditated murder said the state. and as evidence of clay starbuck's twisted state of mind, the prosecution offered this final p