I wouldn't be expecting an arrest in this case soon. The QPS will almost certainly have enough circumstantial evidence to charge someone with a manslaughter by now, and probably a growing body of direct evidence. But there is no real point in an arrest until they have determined whether there is enough evidence of intention to ground a murder charge. Given that a manslaughter conviction without any strong evidence of the exact circumstances of the killing would probably only result in a few years in prison (perhaps 3-5), compared to a minimum of 15 years for a murder conviction, it's important to exhaust the investigative process beofre moving. The manslaughter evidence isn't going anywhere and once charges are laid the accused person will be either put in a remand centre or very carefully managed by their lawyers. In either case, the accused will not be then out and about to make some potentially incriminating statements or actions and will not suffer anywhere like the amount of mental stess that they would be under if there was still uncertainty about whether they were even going to be charged. The actual killer's mind will be racing at the moment and that's the sort of mind detectives like to interrogate. They can use that stress to their advantage. Unless a suspect is a significant threat to other people, arresting or charging them isn't a priority. It's getting the best prosecution outcome that matters. And if that means letting suspects stay in the community for months, or even years, then that's what is done.
