You may have an IQ of 88.  You may have chronic brain damage.  You may have a history of seizures.   Your brain -- at least according to the CTs -- may have weirdly shrunk.  Perhaps all of these due to (and certainly not helped by) being hit by a car when you were riding your bike in seventh grade, plus two motorcycle accidents, plus a car accident.  All of which knocked you unconscious.  Yes, all of these may well be true.
But you killed a four-year old kid.  For $250.  Which you negotiated up from $150.
That's going to get you sentenced to death by pretty much everyone.  In legal parlance:  No prejudice.
So holds the Ninth Circuit.