Okla. Stat. tit. 21, § 701.9

A. A person who is convicted of or pleads guilty or nolo contendere to murder in the first degree shall be guilty of a Class Y felony offense and shall be punished by death, by imprisonment for life without parole, or by imprisonment for life. A person who is convicted of or pleads guilty or nolo contendere to murder in the first degree, as described in subsection E of Section 701.7 of this title, shall be guilty of a Class Y felony offense and shall be punished by death or by life without parole and absent an overwhelming amount of mitigating evidence shall not be entitled to or afforded the benefit of receiving imprisonment for life or deferment of the sentence. B. A person who is convicted of or pleads guilty or nolo contendere to murder in the second degree shall be guilty of a Class A1 felony offense punishable by imprisonment in the custody of the Department of Corrections for not less than ten (10) years nor more than life.