When Adam Lanza walked into a school in Connecticut and shot the place up the justice system got clearance to screen his DNA to look for this "warrior gene".
It's clear that there is a belief amongst people that this must be the reason why mass shootings occur in America. But what people are refusing to acknowledge is that we (the West) have a system that allows for winners and losers. In this system some people will fall through the cracks and become disenfranchised. Unfortunately this festers until someone total loses connection with the rest of society and flips out.
Adam Lanza, over a period of time, began to fall further and further away from society until he got to the point that he believed people to be undeserving of life.
Venables truly did believe that Jamie Bulger was "just a divvy". That he had zero value in the world and that it, in his mind, didn't mean all that much to kill him.
How did he come to that point? He wasn't born that way. Society as a whole let him fall through the cracks. His parents did nothing to bring him up properly, the school system did nothing to identify that this boy was falling out of society. His teachers described him as "horrid" but nothing was ever done.
@Vonhelmet professes the virtues of rehabilitation. He's right to do so but rehabilitation needs to happen BEFORE a crime is committed but are we, as a society, really prepared to start interfering like that with people's lives? Are we really going to stop useless people from having children, taking children from their parents at the first sign of trouble?