I agree with you that CW killed the girls first and then killed SW as soon she arrived home. As far as the phone, I believe it ended up on the sofa when CW killed her. I base this on the evidence and on what I've read about SW. First, NAU dropped SW off, and from all that I've read, I have to believe she didn't see CW. He didn't greet them. Her description, if I'm correct, was that she watched SW get out of the car and go into the house and then she (NUA) left. Next, inside the house, SW left her purse, suitcase, keys, and shoes by the door. That was out character! She was about being clean and organized and would have carried everything upstairs to the bedroom. Even if she was tired. I believe she set everything down, took off her shoes to be quiet, and rushed upstairs to see her children, out of concern. Her cell phone would have been in her hand, because to her, it was a necessary appendage like her arms and legs. Once she was upstairs, the nightmare began. I believe CW wanted her to see the dead children. A macabra " see what you made me do!" moment. In that moment he attacked and they ended up on the sofa, with her probably face down, and the phone under the pillows/cushions. When it was over, CW sat and thought about what he had done and probably ordered, in his mind, what he needed to do next. How long he sat and what he felt and thought is left to conjecture, at least until the trial. (autopsy results may answer some questions) Meanwhile, his schedule had been thrown off by the late flight. He probably could have gone out at 11:30 or even midnight without arousing suspicion (again, in his mind), to take care of "business", but 3 or 4 A.M. would be hard to explain. So, he had to wait until time to go to work. What did he do? A nap? I don't know. He probably did carry SW into the bedroom and placed her on the bed, on top of the fitted sheet. That might explain his "she had barely got into bed" statement. And, there probably was some last minute preparation, before he loaded the truck and left at 5:15 A.M. Upstairs, the phone was lying somewhere on the sofa, waiting to be discovered. I wonder if he thought about where it was when he called and texted her? Or, when he was racing to the house to meet NUA and LE? I wonder if LE asked him to call the phone so they could listen for ringing? Anyway, IMHO, that is how the phone ended up on the sofa.
