Psychopaths, humanity, and the criminal law

According to Stephen Pinker:

Psychopaths make up 1-3 percent of the adult male population [depending on definition] ... [They]  are liars and bullies from the time they are children, show no capacity for sympathy or remorse, make up 20 to 30 percent of violent criminals and commit half the serious crimes. They also perpetrate non-violent crimes ... The regions of the brain that handle social emotions, especially the amygdala and orbital cortex, are relatively shrunken or unresponsive in psychopaths, though they may show no other signs of pathology.' (Pinker, p 615.)

If this is true (and that a diseased brain causes a person to be a psychopath, rather than the other way around and rather than the whole thing being a lot more complicated), what does this mean for the criminal law and justice?

I wonder it means, at least, that our prisons should be humane places. We may have to deprive certain individuals of their liberty, but perhaps that is the extent of society's remit to punish and protect?