This might be a good time to review the formal definition of murder in the state of NSW where charge of murder against JS has been laid. It is contained in Section 18 of the NSW Crimes Act, which I reproduce in full here:
18 Murder and manslaughter defined
(1) (a) Murder shall be taken to have been committed where the act of the accused, or thing by him or her omitted to be done, causing the death charged, was done or omitted with reckless indifference to human life, or with intent to kill or inflict grievous bodily harm upon some person, or done in an attempt to commit, or during or immediately after the commission, by the accused, or some accomplice with him or her, of a crime punishable by imprisonment for life or for 25 years.
(b) Every other punishable homicide shall be taken to be manslaughter.
(2)(a) No act or omission which was not malicious, or for which the accused had lawful cause or excuse, shall be within this section.
(b) No punishment or forfeiture shall be incurred by any person who kills another by misfortune only.
View - NSW legislation
We've heard various MSM reports of what the police believe and what lines of inquiry they're taking, but as far as I know the recent press conference is the only official statement from them since the charge was laid.
I've transcribed as carefully as I can two key relevant questions and answers to the NSW Deputy Commissioner for police at the media conference that followed the accused's court appearance on 19 January.
[
At 10:20 in the press conference] In response to a question about what the police believed happened to CM.
"Last night we obviously found the remains - human remains consistent with the missing girl. Until the post-mortem is conducted
we are still uncertain of what exactly happened to her.
What we are sure of is that the accused that we charged with murder was responsible for personally placing her in the barrel and disposing of that barrel in the bushland where she was located. So as the Commissioner indicated we are very much in the early stages of this investigation. Things will unravel over the next week or so, to find a cause of death and a purpose for her death and try and identify exactly what happened so that the remaining family have some comfort in that." [my emphasis]
[At 11:08 in the press conference] In response to a question about whether the police will be alleging that the accused acted alone:
"We don't speculate in relation to investigations, we investigate. The investigation will be ongoing. At this stage we have no evidence to support anything else than the accused acted alone. However it's still early days in the investigation."
The press conference can be viewed here:
It's worth comparing the responses of the Deputy Commissioner with the Crimes Act's definition of murder. The things he says he is "sure of" do not by themselves (but criminal lawyers please chime to correct me here) seem sufficient to sustain a charge of murder. In particular he does not say they are sure the accused caused her death.
It sounds like the police are waiting for the autopsy results and whatever emerges from ongoing investigative activities and information from the public, to firm up the evidence for murder.