Agreed. He’s seen the evidence and is still pleading not guilty, so what’s his goal besides complete exoneration? Is he trying for a lesser charge like manslaughter, or is he banking on ‘no body, no proof of a crime, nothing to see here’, or is he intending, once his options run out, to negotiate for a reduced sentence by handing over the body? Nevertheless, even if he wanted to portray it as manslaughter, the body was moved. It could simply be a display of unwavering opposition and defiance, in spite of the clear evidence and expert counsel.I think since he's pleaded "not guilty", he must think he is able to offer an alternative to the allegations.
He doesn't necessarily need to do that since he's already considered innocent.
He's seen the evidence against him and must know that the police are relying on some particular point that he can refute and show there is alternate conclusion.
I would expect he has been informed of the different outcomes of pleading "guilty" versus not. The difference would be significant for his sentence so he's got to be feeling confident he can present a jury an alternative that is a good reason to doubt the prosecution's theory.
...or he is just a silly, silly boy.
JMO

Murder and Manslaughter (Vic)
There are a number of crimes relating to unlawful killing under Victorian criminal law. These include murder, manslaughter, constructive murder, single punch manslaughter and voluntary manslaughter. Different degrees of blameworthiness attach to different offences involving the death of a victim.
