In all cases tried by a jury in which the penalty of life imprisonment without parole may be imposed pursuant to § 11-23-2 or 11-23-2.1, and in which the attorney general has recommended to the court in writing within twenty (20) days of the date of the arraignment that such a sentence be imposed, the court shall, upon return of a verdict of guilty of murder in the first degree by the jury, instruct the jury to determine whether it has been proven beyond a reasonable doubt that the murder committed by the defendant involved one of the circumstances enumerated in § 11-23-2 or 11-23-2.1 as the basis for imposition of a sentence of life imprisonment without parole. If after deliberation the jury finds that one or more of the enumerated circumstances was present, it shall state in writing, signed by the foreperson of the jury, which circumstance or circumstances it found beyond a reasonable doubt. Upon return of an affirmative verdict, the court shall conduct a presentence hearing. At the hearing, the court shall permit the attorney general and the defense to present additional evidence relevant to a determination of the sentence to be imposed as provided for in § 12-19.2-4. After hearing evidence and argument relating to the presence or absence of aggravating and mitigating factors, the court shall, in its discretion, sentence the defendant to either life imprisonment without parole or life imprisonment. If the trial court is reversed on appeal because of error only in the presentence hearing, the new proceedings before the trial court which may be ordered shall pertain only to the issue of sentencing.