If I remember correctly all serial killers that have had their brain studied have all had damages in their frontal lobes. Serial killing is much like any dysfunction. They're as much a genius as a person in a wheel chair. The reason they see killing other people as a rational solution to a problem... is because it is. The rest of us have an irrational instinctive block to think murder is wrong. There is no rational reason why the killing of another human is wrong. That's just how human instinct works. It's an instinct that has served humanity well in the past, and probably will in the future. Can we over-ride it... hell yes. That's what self-consciousness is. We can do it... but it makes us feel bad. At least if we have a healthy brain.