Tennard v. Dretke, 124 S. Ct. 2562 (2004)
In Penry v. Lynaugh, 492 U.S. 302 (1989), the U.S. Supreme Court established that a defendant's mental retardation is a potential mitigating factor at capital sentencing. Under Texas law, however, a finding of mental retardation was limited to where there is subaverage general intellectual functioning, concurrent deficits in adaptive behavior, and onset during the early development period...