Eighteen males condemned to death in Texas for homicides committed prior to the defendants' 18th birthdays received systematic psychiatric, neurologic, neuropsychological, and educational assessments, and all available medical, psychological, educational, social, and family data were reviewed. Six subjects began life with potentially compromised central nervous system (CNS) function (e.g., prematurity, respiratory distress syndrome). All but one experienced serious head traumas in childhood and adolescence. All subjects evaluated neurologically and neuropsychologically had signs of prefrontal cortical dysfunction. Neuropsychological testing was more sensitive to executive dysfunction than neurologic examination. Fifteen (83%) had signs, symptoms, and histories consistent with bipolar spectrum, schizoaffective spectrum, or hypomanic disorders. Two subjects were intellectually limited, and one suffered from parasomnias and dissociation. All but one came from extremely violent and/or abusive families in which mental illness was prevalent in multiple generations. Implications regarding the ethics involved in matters of culpability and mitigation are considered.