Moral culpability in Harry Potter series

It seems that moral culpability in the world of Harry Potter mirrors the teachings of the Catholic Church about certain intentions being necessary for an individual to be personally guilty of an evil action. At the end of "Order of the Phoenix", Harry attempts to use the Cruciatus, an "unforgiveable curse", against Bellatrix Lestrange to avenge the death of Sirius Black. Bellatrix explains why it doesn't work "righteous anger won't do" and "you have to really want to cause pain." So in Catholic moral theology one who doesn't realize what he is doing can perform an evil action but not know or understand that it is objectively wrong and therefore cannot be held personally culpable. Harry was unable to make the curse work; likewise the ignorant person would be unable to commit a sin. Bellatrix could be seen as the responsible party, however unlikely, for the formation of Harry Potter's conscience in this matter. It could be argued that had he attempted the Cruciatus against her again and succeeded that he would be culpable and worthy of Azkaban. However this does not happen.