Cotter Park is the nearest caravan park or camping ground to Wallaroo NSW and it is on the outskirts of Canberra.
On the outskirts of Canberra, this is a very popular campground with hot showers, alongside the Cotter River.
The campground is very large, with separated areas for different types of camping (caravans, tents etc)
http://www.findacamp.com.au/camp-site.php?pc=WALLAROO_NSW_2618&dis=25&camp=367
My current thoughts are that DH, Karlie and Khandalyce stayed in a place like this the whole time that they were in the Canberra area
*as it is cheap,
*they are alone,
*they had an argument over money and/or her car
*and/or KP threatened to tell HP that they had had an affair
*and/or KP found out some secrets about DH which she did not approve of,
*HP is calling DH to pressure him to be back in Adelaide for Christmas as she is coming out of rehab. hence the pings on his phone perhaps? Who else would be phoning him on 14/15 Dec and 19/20 Dec?
*DH could have threatened KP with some sort of weapon eg knife (if she did not tell him her pin nos, passwords, etc.)
So after she told him, he had no further use of KP so he either suffocated or strangled her as it had to be a quiet murder if they were in a caravan park.
Hopefully Khandalyce was asleep. So in the middle of the night, he takes KP's body to Belanglo National Park and dumps it there to confuse police. Khandalyce is either put in the car seat of Karlie's car (or he leaves her there asleep in the caravan?). He dumps the body and returns quickly. Next day, he withdraws money from her bank account with Khandalyce in tow who is not very happy as she does not know where her mother is and she gradually puts on more and more tantrums so he finds it difficult to manage her. He decides to ask his sister to mind two bags while he is away.
On the last night, he suffocates or strangles Khandalyce and puts her body in the suitcase then in the car boot. The manager (or others there) of the caravan park when DH is leaving notices that Karlie and Khandalyce are missing but does not think anything of it as DH tells him a story until the police ask him about DH years later (or he phones CrimeStoppers). DH drives to Wynarka on the back roads avoiding police and dumps the suitcase.
The reason I say this is I just cannot see how DH could get KP willingly to drive to Belanglo National Park unless she was forced to under threat and to have a live child there with them too. I guess he could have told her that it would be nice to have a picnic there!
However, we have only been told that Khandalyce died in Wallaroo due possibly to his mobile pinging there for about 24 hours. It also gets complicated if they were staying with friends and Karlie disappears leaving DH with Khandalyce. If they stayed with his sister, has she been privy to covering up or did he tell her some credible stories about Karlie's absence?
You are now free to pick holes in my theory.