Moral experts are best defined as those who have studied moral questions carefully, know the main theories developed in response to such questions, and (where possible) know and are able to offer arguments that would convince reasonable people.
In scientific and technical areas, one important feature of a successful answer is that it works, in the sense that it makes accurate predictions. We can say that successful answers to moral questions take the form of arguments which, if examined carefully, would persuade reasonable people and lead to convergence in their moral views.
The moral responsibility of individuals for themselves does not preclude the role of moral advisor. Many self-pronounced moral experts might be interfering, condescending and hypocritical, but such characteristics need not accompany moral expertise. Probably no one could claim a high degree of expertise in all areas of ethics.
