jeffa - "Do you think that this murder would have happened if somewhere in the darkest recesses of the warped minds of the perpetrators a little voice had said, "Remember that when you are caught tried, and found guilty you will hang by your neck until you are dead."?"
Yes.
Because people like this are so caught up in their own outrage and sense of 'rightness', that the notion that anyone would not carry them shoulder-high round the town en route to tea in the mayor's parlour would never come anywhere close to their minimal intelligence.
You are assuming that people like this are able to think outside their instincts far enough and long enough to understand that actions have consequences. In doing so, you are awarding them a basic level of intellignce which they clearly do not possess.
No-one who murders someone ever thinks they will be caught, tried and executed. If they did, the U.S. states that employ capital punishments would all have murder rates of zero.
They don't.