What role does theory play in the criminal justice system?what happens from the commission of a crime, to the investigation of that crime, through...

Two examples:

As the previous post points out, our prisons are meant to be a deterrent.  Ugly prisons, long sentences, etc., all these are meant to scare people away from committing crimes.

In Norway, the focus is on rehabilitation and preparing a criminal to be able to reenter society and to do so effectively.  This means that their prisons are completely different than ours and are often not scary at all.

But these theories affect everything, sentencing, the actual processing of crimes, etc.  Even the investigation is changed by the way the society approaches crime and punishment in theory.  If you want to help the person not do it again, you will look for different clues than if you want to simply prove beyond the shadow of a doubt that he did it.