I had a very bad experience with someone I now believe fits the diagnosis of psychopath. One of the things I've learned in researching since, is that the psychopath (and sociopath as well) are very convincing manipulators, can mimic all the rhetoric, they've learned over the years, of being a productive, caring, and even empathetic human. I watched a very informative video on youtube just this past week by the man who formulated the "Psychopath Test," in which he was working with hardened criminals, the worst of the worst. Hearing some of these men talk, they sounded so normal, while speaking at the same time of their horrendous crimes as if talking about a grocery list.
I'll see if I can find the link.