When developing our characters, we want to avoid stereotypes and oversimplification. According to The Criminal Mind by Katherine Ramsland, PhD, one of the easiest ways to avoid this is to research journals and case histories. Review an actual case and use that case to spin our characters. "The more life details you can find, the more believable the character will be."
Ramsland suggests perusing psychology journals, criminal behavior journals and forensic psychology journals.
http://www.authorsden.com/visit/viewArticle.asp?id=28821 This links to a case study written by Sam Vaknin profiling a patient with narcissistic personality disorder. This patient just happens to be a writer.
How could we spin this into a believable character? In this case study, the patient did not commit any crimes but with a writer's imagination, "Sam" could be turned into a wonderful criminal.
I would love to see your ideas on how to spin Sam into a deliciously evil antagonist!