What is the current state of the law in the context of mental impairment in a criminal case?

5 We are not concerned with a situation in which a convicted defendant, endeavoring to mitigate a sentence, offers evidence of bizarre behavior to show a mental impairment that might justify leniency, thereby accepting the risk that such conduct might be perceived as an aggravating circumstance. See Granviel v. Estelle, 655 F.2d 673, 675-76 (5th Cir.1981), cert. denied, 455 U.S. 1003, 102 S.Ct. 1636, 71 L.Ed.2d 870 (1982).