That's an understatement.
It's nailed on that SJ murdered Billie-Jo. During the case, it came out that SJ was a violent, controlling father/husband who had a short fuse. Billie-Jo was painting the doors that morning as punishment, so there was friction between them. SJ takes his other daughter on an unplanned trip to the DIY store and drives around the neighbourhood twice before realising he's "forgot" his wallet. The trip takes around 15-20 mins, leaving a narrow window of opportunity for Billie-Jo's murder. When they return home, SJ makes the peculiar move of leaving Billie-Jo's body to sit in his car for emergency services to arrive. It's been suggested that SJ did this in case any traces of Billie-Jo's blood were found in the car. At the retrial, the prosecution tried to bring late evidence that showed SJ's clothes contained Billie-Jo's bone fragments but it was refused by the judge. In the interests of justice this evidence should've been admitted and may have secured SJ's conviction.
If that wasn't damning enough, SJ wrote that while the paramedics were tending to Billie-Jo, he spoke to a plain-clothes officer who consoled him. As there was no plain-clothes officer on duty, SJ believes this man was actually Billie-Jo's killer. That's right, Billie-Jo's killer didn't escape while the coast was clear. Instead, he waited in the house and then made himself known to the victim's father. That's the problem with a compulsive liar like Sion Jenkins - they don't know when to shut up.
It's appalling that Billie-Jo's future was stolen, while SJ lives as a free man and has suckered another woman into marrying him.