OK, so let's assume that LE know the offender's identity, or reasonably suspect a particular person. Obviously that alone is not enough to make an arrest. And under double jeopardy statutes, which I believe exist in most countries, they really only get one chance to get it right. My knowledge of Australian law is limited to a little bit of TV, a little bit of news and a little bit of wikipedia. So, "means, motive and opportunity" I understand is some kind of rule of thumb for the elements required to lay charges - not necessarily a mandate. I think from memory I've seen some US based crime docos which make mention that certain things must be present before a murder charge can be laid, such as a body, a murder weapon, and in the absence of any on of whatever these things are, they cannot lay a murder charge. My question: Does Australia/NSW have any similar requirement for laying charges for murder? Or can murder charges be laid on little evidence provided the jury can be convinced of the suspect's guilt by the prosecution? My guess is that the only thing delaying the arrest at the moment is LE needing to physically place the main suspect at the scene of the crime at the time of the crime. If that was with DNA evidence, I would have thought an arrest would be made by now (how long does DNA testing take?). Of course, if that DNA evidence was not blood, but other body fluids, then the timing of the suspects presence at the scene could possibly still be argued. Does LE need to obtain a warrant in order to test a suspects clothes for traces? And if so, on what grounds can they obtain that warrant? Must they already have something solid to justify it, or is suspicion enough? And maybe not. Maybe all they need to do is piece together a plausible sequence of events and movements, and then provide evidence to back it up (CCTV, witness sightings, etc)? Is there a legal buff here who can help fill in the gaps in my knowledge?