When a longer sentence is allowed for second degree murder

(a) The court may sentence a person who was twenty-one years of age or older at the time of the offense and who has been convicted of murder in the second degree to life imprisonment without the possibility of parole under section 706-656 if the court finds that the murder was especially heinous, atrocious, or cruel, manifesting exceptional depravity or that the person was previously convicted of the offense of murder in the first degree or murder in the second degree in this State or was previously convicted in another jurisdiction of an offense that would constitute murder in the first degree or murder in the second degree in this State. (b) Hearings to determine the grounds for imposing an enhanced sentence for second degree murder may be initiated by the prosecutor or by the court on its own motion. The court shall not impose an enhanced term unless the ground therefor has been established at a hearing after the conviction of the defendant and on written notice to the defendant of the ground proposed. Subject to the provision of section 706-604, the defendant shall have the right to hear and controvert the evidence against the defendant and to offer evidence upon the issue. (c) The provisions pertaining to commutation in section 706-656(2) shall apply to persons sentenced pursuant to this section. (d) As used in this section: "Especially heinous, atrocious, or cruel, manifesting exceptional depravity" means a conscienceless or pitiless crime that is unnecessarily torturous to a victim. "Previously convicted" means a sentence imposed at the same time or a sentence previously imposed that has not been set aside, reversed, or vacated.