Psych Tomorrow

We are suppose to view a film on the criminally insane tomorrow in psychology. I'm kind of excited. After watching the most recent Batman movies and seeing characters such as the Joker and Scarecrow it makes an individual wonder whether people like that actually do exist or if the characters are a little over the top. Obviously having no compassion towards another member of the human race is inhuman. Anyone who is able to do so in my opinion lacks certain mental capabilities. At what point does someone become insane? I hope to learn this tomorrow and elaborate on it later on.