Should someone stand trial

three times for the same murder?
There is a long running legal saga in this state which has recently been under review - yet again.
It has been a case of interest to my family. My mother knew the father of the alleged victim. I have to say alleged here because, although she died, there is some doubt about how she died. My mother did not know the father well but she liked what she saw.
The man who is alleged to have murdered his daughter was put on trial in 1995. The first trial resulted in a hung jury. The second one found him guilty and he was sentenced to a minimum of twenty years. He served almost the entire twenty years before being released - on bail. He had appealed his conviction under new legislation - something which would not previously been possible.
The DPP now wants a third trial.
I know more than I might about this case because my nephew was the one who had to read the transcripts and the evidence and provide the material which the barrister used to get  this man released on bail. And yes, there is much more to the case than the media ever reported. I can't say more than that.
What I can say is that I wonder why the DPP is so keen to have a third trial. What is it they want from it? If this man is found guilty again then there will be the question of whether he is returned to prison to serve yet more time but it seems unlikely. If he is found not guilty then there will be other and even more complex issues raised. 
Murder trials are expensive, very expensive. There will be particular difficulties in this one. There were evidentiary issues right from the start. 
In all the media coverage of the case something else went unnoticed. There is another man in prison in this state. He could have been released some years ago - if he admits his guilt. He has apparently steadfastly refused to admit his guilt. I don't know who he is or what the circumstances of his case are but I wonder why anyone would remain in prison if they could leave. I am aware there are people who return there again and again. I am aware that there are people who feel "more secure" there. They get fed and housed and other people tell them what to do and, for sad and tiny minority of people life "inside" is better than life "outside". 
But if someone really was innocent and could leave only by saying "Yes, I am guilty" then what would the choice be? Lie and lose any chance of being found innocent - or risk never getting parole?
"There's a book in all that," a friend told me.
Yes, the plot has been used before - more than once. Real life is another story.