The mental illness defense in the capital penalty hearing

Several defense strategies are available to the capital defendant who is arguing for life in the penalty phase, including a mental illness (MI) defense. An MI defense presents psychiatric testimony to the effect that the defendant was mentally disturbed at the time of the offense and, therefore, should not be held completely responsible. The few studies available suggest that an MI defense will be ineffective because (1) death-qualified jurors do not respond favorably to purely psychological explanations of criminal behavior and (2) an MI defense may erroneously mislead the jury regarding the defendant's unpredictability and dangerousness. Analagous studies of insanity acquittals suggest certain factors that may be associated with a succesful MI defense.