For people who lack the ability to feel emotions or to empathize i.e. sociopaths, they still held responsible for their crimes. Of course. But, if humans are only material beings, and if their sociopathy is a brain disorder, and if the center of knowing right and wrong is in the brain, how can we hold someone responsible for their crimes? After all, it's a brain disorder, and the brain determines behavior. Nothing else does.

But if humans have a soul, this makes things entirely different. Of course it does. We can dig deeper, however. Let's leave discussions of the soul aside for the moment, because not all people believe in a soul. There are arguments for the soul, sure--and they're robust and good arguments. Still, let's understand human beings of having an intellect and a will. (Surely there is more to us than that, but it's a good place to start). The intellect and the will are two primary aspects of human beings, especially in terms of ethics and morality.

A person's reason is involved in both the intellect and the will. The emotions, as subservient to the intellect and the will, are therefore not the primary center of determining the difference between good and evil. An evil man who kidnaps, rapes, and kills women, but who is a sociopath, even though he lacks the ability to have sympathy and empathy, nevertheless knows what he is doing is evil. His reasoning process, through his intellect and will, while they tell him what he is doing is good for him, nevertheless also inform him of his evil acts. He knows what he is doing is evil because he knows he is taking from others what rightfully belong to them: their freedom to be and to live and to pursue happiness. The evil man knows he is acting out of the order and fabric of the created order because he is violating the nature and essence of his fellow humans. And it is the nature and essence of things which speak to the intellect and the will, telling the evil man that what he is doing is, in fact, evil.

Someone's brain may be unable to foster emotive responses toward the suffering of others. This does not exclude the sociopath from a philosophical or scientific excuse for his evil, and he should be punished according to his crime.