Did you see this article? http://www.wset.com/story/26669474/classmate-of-jesse-matthews-speaks-out
One of JM's classmates from LU say's JM is basically slow and she would help him with his school work.
Coral Eugene Watts killed a lot of women and Watts suffered from mild mental retardation with a I.Q. of 75 and he had a delusional thought process. He also had a 3rd grade reading level when he was 16.
JLM had a lot of street smarts, but not book smarts. Unlearned, but corrupt (covetous, vengeful, angry, greedy) people have victimized their intellectual and moral superiors from the beginning of history. Look at Genesis 4.
The defense will have to prove scientifically that JLM was incapable of right judgment, not culpable for his actions, had brain damage, etc. (PET scans, empirically proven standard psychological examinations) and face an expert to prove JLM didn't know what he did was wrong, legally or morally.
Very unlikely, since he graduated from high school, held down jobs, carefully hid all his bodies, drove across the USA and changed his appearance so not to resemble the first Fairfax rapist sketch.