(4) Forcible sodomy is a first degree felony, punishable by a term of imprisonment of:

1. (a) except as provided in Subsection (4)(b) or (c), not less than five years and which may be for life;

2. (b) except as provided in Subsection (4)(c) or (5), 15 years and which may be for life, if the trier of fact finds that:

   1. (i) during the course of the commission of the forcible sodomy the defendant caused serious bodily injury to another; or
   2. (ii) at the time of the commission of the rape, the defendant was younger than 18 years of age and was previously convicted of a grievous sexual offense; or
3. (c) life without parole, if the trier of fact finds that at the time of the commission of the forcible sodomy the defendant was previously convicted of a grievous sexual offense.

(5) If, when imposing a sentence under Subsection (4)(b), a court finds that a lesser term than the term described in Subsection (4)(b) is in the interests of justice and states the reasons for this finding on the record, the court may impose a term of imprisonment of not less than:

1. (a) 10 years and which may be for life; or
2. (b) six years and which may be for life.