The more one takes I.Q. tests, the less reliable they become. My wife's I.Q. is so high, is essentially unmeasurable. Why? She has taken the Weschler Adult Intelligence Scale 2 (WAIS 2) 20+ x in her education as a clinical therapist. Both her and I have worked with criminals in many ways, and I.Q. tests are a very small part of an overall assessment for mental ability.
The term mental retardation is loosly thrown about, in the Texas situation and others. What is mental retardation today is not what it was 20+ years ago. This has changed not only in clinical applications/therapy, but in what criminal courts determine to be "competent." If you got the money, and the standing, and this is sad to say, you can find someone with a "Ph.D" after their name to tell them you are the most F'd human they'd ever met.
Most criminals test lower in nearly every performance dimension one could think of, but, they aren't that much lower than the kid who made your last espresso at Starbucks.
I believe that murder while in the commission of another felony is the standard in Texas, and in most states.
p.s., my wife is the smartest person I know. And those days she's NOT the smartest person I know, I still let her think that.
Mike