On the stand he repeatedly mentioned the concept of temporary insanity. Certainly that line of defense must have been explored?That is only my speculation.
Because that was really his only (possible) defense -- some sort of mental defect -- I do wonder why he wasn't evaluated, or if he was, why it didn't factor in the trial.
It would appear the defense didn't intend to put on a defense, probably did everything to discourage him from taking the stand (for fear it would go exactly as it did).
Really sad case, all around.
JMO