The ethics textbook I use is called Moral Competence, and its focus is just what it says it is. The book develops a five-fold model of a morally competent decision maker. Although the book is riddled with arguments--for instance claiming that virtue alone, as the book defines it, is not sufficient for moral competence--it doesn't make an effort to empirically verify the system as a whole. This makes sense for what the book is trying to do. The model is presented mostly as a framework for students to deliberate on their own moral competence and for synthesizing results and ideas from a wide range of philosophers and psychologists.
Still, something could be gained by looking at the ways that other disciplines have developed models of competences and verified them. The focus on language competence in Chomskian and post Chomskian linguistics would be a good model. A lot of emphasis is placed there on error patterns. It is a big deal that children frequently overgeneralize grammatical rules, but never simply spit out strings of words without any grammar. Something similar happens in neuropsychological models of different abilities. A stroke can impair one aspect of the ability but not another--for instance a patients ability understand written number words like "One thousand fifty four" but not Arabic numerals like "1054"--and this says something about how we model the competence.
I'm trying to figure out what the equivalent data for moral failings would be. Liszka's system encompasses many classical distinctions between kinds of moral failings, such as Aristotle's distinction of failures of knowledge and failures of will. It also brings in psychological theories of failure, like ideas about anti-social personality disorder and failures of empathy. But I still don't have a good sense of what the data to be explained is.
Are there kinds of moral failure we just don't see, akin to Chomsky's grammatical mistakes that don't get made? Are there cases of selective impairment that would help us here?
If I still had time for a research program, I would do more reading in the moral psych literature to figure this out. Right now, though, the things I've seen really work orthogonally to this issue. So now I'm just wondering out loud.