I am going out on a limb here and saying in my opinion, DM may have asbergers syndrome. Here is a link describing the symptoms and you can pretty much, just from what we know so far about him, fit any symptom into his behaviour. Above average intelligence, engineering and mechanics, eating the dog cookies, not fitting in, not very many friends, lack of empathy. Have fun with this, because in every single symptom we find a trait of DM, younger friends etc.....
http://www.wisegeek.com/what-are-the-main-symptoms-of-aspergers-syndrome-in-adults.htm
Read this article as well about what his friends say about him
http://news.nationalpost.com/2013/0...riends-remember-him-as-attention-seeking-kid/
Now, my question is,,,,,,, Can asbergers syndrome be used as a defense.???
Maybe, just maybe, this is why we just can't figure him out regarding motive.