I think it is an old American thriller. Possibly early 2000s. A female student attends the criminology course. I remember the professor argues why serial killers succeed in ingratiating themselves with the victims, e.g. Ted Bundy who seemed to be a perfect gentleman.
There was a male student who was in love with that girl but she fell for that professor. And at the end he turned out to be a serial killer.
Murder 101?