District court's grant of defendant's petition for habeas relief in part, from a murder conviction and sentence of death, in concluding that defendant was denied his right to effective assistance of counsel at sentencing, is affirmed where: 1) district court's denial of habeas relief on defendant's claims of ineffective assistance of counsel in the guilt phase, insufficient evidence of prior calculation and design, and failure to instruct the jury on lesser included offense of involuntary manslaughter is affirmed; and 2) district court's grant of habeas relief on defendant's claim that he was denied effective assistance of counsel in the penalty phase is affirmed as it is reasonable probable that at least one juror would have voted against death had defense counsel presented the mitigating evidence at issue.