Gotta ask you barrister types:
He has pled not guilty by reason of mental disease or defect. Is that not the same as saying "I did it, but I am fucked in the head, so I should not be held accountable"?
If you think you are innocent, then plead "not guilty". How mentally fucked up you are should not be an issue at that point if you are innocent.
To me, that choice of plea is an admission of guilt, with an attempt to mitigate punishment by claiming you are brain damaged.
Yes? No?