This was the first time that I have seen the interview of Sion by Trevor McDonald, so thank you to Mystar for posting it. In part one Sion makes a very valid point which has not been discussed here. That is the journey that Sion makes to Do-It-All having left Billie behind to paint the patio doors.
Firstly, let us take the prosecutionís version of events at face value; in which case at the time that Sion leaves for Do-It-All with the two girls, he has already killed Bille-Jo. So while embarking on this journey there are two key points he would have had to consider: Firstly, he has to think about what he has done and formulate a plan to cover his tracks. Secondly, in order for Sionís explanation that Billie was killed by an intruder to have any credibility then he needs to create as large a time window as possible. Therefore, on arrival at Do-It-All he would have parked up, wandered around the store, wasted time, picked up items almost at random. Even if he had known he had gone in without his wallet, he would have pretended not to and only made an issue about having no means to pay once at the cash register.
But the reality is that he does none of this. Sure, he makes the one circuitous route to the store, but he explains all this and the girls had reported nothing odd about it in their original statements. They get to the store and he turns round in the car park, returning directly to their home. As a result of which, the defenceís version of events refers to an incredulous albeit possible window of opportunity for an intruder to enter the back garden and murder Billie.