The thing you need to get into perspective is that to the ordinary person in the street such crimes are abhorent, and you couldnt even think of doing them. Moving on from that, most normal decent people have a respect for the law and the judicial system and the sentances that are passed. They must do or the system wouldnt still be in place. Many of these sort of crimes are carried out by many who are not normal decent people and dont have a regard or an undersatnding of the law, or even a moral view of right or wrong.
Many of these crimes are carried out in an enclosed world where authority is a meaningless concept that lives outside the front door. When it does come into their house or their lives, and they cant deal with it or understand it when it does. Therefore whatever sentance you pass on one person who carries out such a crime, it wont have a deterant effect on certain people and so similar crimes will continue to happen. Fortunatley they are not that common, but they have been going on for years in all countries regardless of the deterant of the sentance. At present the mandatory sentance for murder is life (i know they dont stay in for that long) but that doesn't stop people carrying out such acts in a few minutes of mindlessness.
I've dealt with all sides of many of the crimes that turn your stomach when i was in the police. I've dealt with the victims, the families,the neighbours, communities, the offenders, and the judicial system. The only conclusion i can draw is that if a person is going to commit a crime they will do so, regardless of the law, because its either in their make up or they've been affected in some way (ie drink/drugs, emotions etc) It doesnt stop my blood boiling and feeling the way most people do.
I dont know what the answer is, and I dont think anyone else really does.