It is my understanding that psychopaths know right from wrong and can fit into society if they choose to. Often psychopaths can become extremely successful in business, politics and the entertainment industry as they have the ability to manipulate people without any reserve. It is clear then that many psychopaths can control their behaviour, but are more willing to choose to hurt others if it benefits them to do so. They will also seek to conceal their crimes - another indicator that they know that their actions are wrong. Psychopathy is not the same as mental illness, and is classed as a personality disorder. These are conditions with long term, maladaptive (either to self or society) traits. In the UK, people with persoanlity disorders are held responsible for their actions because they have a choice. I would guess that the Church holds the same view - although the extent of guilt is for God to judge. The best estimates by Psychologists are that 10% of the population fit the criteria for psychopathy - very few are violent or become serial killers - thankfully! However they may be your hard, bullying boss or your selfish manipulative neighbour…
There are both neurological and developmental explanations which probably overlap. The individual may have a vulnerability to a specific of type of frontal lobe dysfunction and this, combined with adverse experiences in childhood may result in psychopathy. There is a real hunt on to track down genetic causes and it’s a question of are psychopaths born or made?
I happen to think that it is both. What we do know is that treatment does not work, the condition must be managed by the person and those around them. Cognitive Behavioural Therapy can help - but it is a very long road. In the UK, violent psychopaths are detained for life. or until they can convince staff that they are no longer a danger - which is not easy!
We all need Grace and I know that God works miracles. In addition, Psychology is not an exact science so our knowledge and understanding are always developing.