In Penrey V

In Penrey v. Lynaugh the Texas Court of Criminal Appeal (the U. S. Supreme denying certiorari on direct review) held that

A) Mental retardation of the defendant prevented imposition of the death penalty
B) Mental retardation of a defendant could be prohibited under certain circumstances but not those posed in this case
C) Imposition of the death penalty was not prohibited by virtue of the defendant's mental retardation
D) Defendants are not allowed in such cases to present evidence of mitigating circumstances