THIS IS JUST A SCENARIO. PLEASE DO NOT REPEAT ANY OF IT AS FACT
The police most likely have their suspect, but for the sake of conversation, let's assume that they only have semen as a match for the DNA; and a witness seeing him at the crime scene (being dropped off in the white ute).
What if the accused initially put suspicion on himself by denying he had been there that night...let's just say because he wanted to protect the daughters reputation, and also his friendship with the best friend. Maybe he did not provide his alibi and admit to being there until they had his DNA match. The police could still hold him for the other charge no matter what...and of all defences to put forth at the hearing, why choose an alibi? It can be dis-proven if you weren't 'there'...why not insanity or self-defence...he still feels he is in a position to deny he did it.
It has been said here the police would make sure they had the right person...and you would hope so (but let's not forget, there was an attempt at protecting his identity due to the doubt an alibi may create). But if he had initially denied being there it wouldn't look good (as his mother said), and once he had been in for questioning again, I would think he would be in danger if released before the arrest of another suspect. Maybe grief and fear kept him quiet initially during questioning.
A couple of things have never sat right with me...firstly, the neighbour who didn't report the screams. Three people were being stabbed to death and fighting for their lives, surely this would sound a tad worse than just a domestic. The houses are so close together it fascinates me how all of this was done so quietly. I would think there should have been a hell of a lot of noise going on, especially if the suspect acted alone.
We know they all fought, and they were all found in different areas of the house. But how could he fight each one off, stab them, and keep them quiet all at the same time? So many things could have gone wrong, and if he did plan this, he certainly seemed prepared to take a lot of risks.
This same name neighbour then puts a rather strange post on his FB expressing regret and saying he wishes he could take back every last bit, and that he never meant to do it. Where as you would think he would be expressing regret for the things he didn't do. (please note we don't have real confirmation on this post as it has since been removed).
(respectfully snipped)
These are just some of the things that bug me about the case. THEY ARE MY THOUGHTS ONLY AND ARE NOT TO BE TREATED IN ANY WAY AS FACTUAL. They are merely food for thought to put it out there that this case is in no way decided based on the information provided to the public (the police may very well see it differently); and it cannot be resolved here without more answers. Hopefully tomorrow will bring more answers, because until we have them, I cannot see how our sleuthing can move forward without becoming pure speculation...