A basic value underpinning our common law is "thou shall not kill", and from this simple moral value the crime of murder has been proscribed. If guilt can be proved beyond reasonable doubt, unless the accused can prove it was an act of self-defence, then the murderer must be punished by the most extreme penalty the law allows. And this has become a crucial part of our notion of justice.
The value is simple and the law is clear, however the courts no longer limit their judgements to the facts, but are influenced by the emotional public response to the claims of the killer; see the cases of Robyn Bella Kina, Dean Waters and Said Morgan. Once the law would have demanded that all these people be hanged by their neck until they were dead, now they are exonerated by the courts.
The tradition of courts resolving only matters of fact has been discarded along with the value "thou shall not kill", so the wisdom of the community that allows the recognition of the evil act of murder, has been eroded. Communal judgement has become so confused that publicly shooting a police woman to death during the execution of her duty is officially considered not a crime.
Justice is the upholding of good over evil, and therefore depends entirely upon the ability to recognise good from evil: a judgement that can only be rational if it is based upon a moral code, which is an unselfish understanding. For if it reflects the judgement of selfishness, an understanding that lacks a moral code, then it must be irrational, and hence unjust: which is why justice is no longer dispensed by Australian courts. (Or even international courts)