The death penalty shall be imposed in all cases in which it must be imposed under existing laws, except when the guilty person is below eighteen (18) years of age at the time of the commission of the crime or is more than seventy years of age or when upon appeal or automatic review of the case by the Supreme Court, the required majority vote is not obtained for the imposition of the death penalty, in which cases the penalty shall be reclusion perpetua. In all cases where the death penalty is imposed by the trial court, the records shall be forwarded to the Supreme Court for automatic review and judgment by the Court en banc, within twenty (20) days but not earlier than fifteen (15) days after promulgation of the judgment or notice of denial of any motion for new trial or reconsideration. The transcript shall also be forwarded within ten (10) days from the filing thereof by the stenographic reporter.