I have an antagonist who survived a violent childhood and more-or-less constant deprivation (little family life, poor access to food and water, exposure, fear of the totalitarian government ruling his homeworld, etc.). The rulers were isolationists and did not allow anyone to leave or visit their world. In his mid teens, he joined a band of freedom fighters, and they overthrew what was left of their leadership. (Isolationism having devastated the ruling class even more than the ruled after about four generations/one century.) They made contact with other planets and set up a new government, with the long-term goal of democratic interaction with other planets/systems. They are trying to undo a century of environmental devastation and impoverishment. (The rulers bankrupted the planet and hid its wealth out of reach before they were finally overthrown.)
Now he's about eighteen years old, working in the diplomatic corps on his homeworld. He makes a decent living and is permitted travel off-world and back to earn his living. But something began to "go wrong" in his mind even before the overthrow, and now it begins to intensify: he nurtures a hatred of his own people and his own skin/form/body. He regards his own people as "weak," "poor" and "stupid" for having allowed the former rulers to do what they did. He obsesses about getting surgery and creating an artificial history that could literally assign him a new name/race/planetary origin. Towards this end, he robs and murders his own people, and begins to collaborate with an off-worlder who promises him the fortune he needs to achieve his goals.
(There is already tech that could give him the outward appearance of being "somebody else," but that isn't enough to satisfy him. He wants the changes to be permanent and immutable once completed. He wants to literally erase his former life.)
I have read through the archives here, and gotten some helpful clues. I have looked up "internalized racism," "race hatred," "self-hatred," "body dysmorphic disorder," etc. (Via search engine.) Some of these are close to what I'm thinking of in terms of my character's "illness." However, I'm wondering if there's another disorder or syndrome that I haven't been able to find.
Are there any verbal slips, pet mannerisms or tics that might give him away to a mental health professional even if s/he didn't literally see inside his mind?
Also, would this be considered a full-blown mental illness? That is, when the character is finally caught, could it be argued that he no longer knew right from wrong? That he was not responsible for his actions, even though they were criminal?
Thanks for your help.