I don't assume anything in the matter, I observe. I can observe they clearly made conscious decisions based on their particular reasons, which were not moral. I also can observe, that there was no organic desease evident.
"Are you now saying that people with "organic diseases" are not capable of evil?"
depends on what it is, and the severity of desease. Certainly, shizophrenia precludes rational functional use, or control of the mind. Manic depression can do the same. It forces emotional control of behavior, rather than rational, or thoughtful control based on such things as prior moral decisions, and value judgments. For very low IQs, behavior depends on what organic emotional drives are present, and what guidance they receive from others.
Good and evil are qualificaitons, that can only be judged on conscious decisions made by a rational being. When rationality is hindered, or made impossible by organic disease, that fact must be considered. No one can change the physics involved in the biology of organic disease by thinking, or praying it away. The chemistry must be addressed to remove the impediment.
Based on your observations? Did you live with Hitler? Did you share a room in college?
Depends on what it is? You have got to be kidding me. Even a mentally challenged person can know the difference between right and wrong.