I bought Hare's and then Cleckley's books on the subject because of x42. He does seem to fit right in.
One of the most interesting things in Hare was the objective test for psychopathy: the subject sits in front of a computer screen, and tries to tell words from nonsense syllables as quickly as possible. Normal people will react more quickly to 'cancer' or 'death', than they would to 'tree' or 'horse'. A psychopath has the same reaction time for all words, presumbaly because their emotions are totally disconnected from their thoughts.
Please ping me if you post the article, thanks.