(a) The governor may, when the governor deems it proper or advisable, commute a sentence in any criminal case by reducing the penalty as follows:

(1) If the sentence is death, to imprisonment for life without the possibility of parole and not to any lesser sentence;

(2) except as provided in subsection (b), if the sentence is to imprisonment, by reducing the duration of such imprisonment;

(3) if the sentence is a fine, by reducing the amount thereof; or

(4) if the sentence is both imprisonment and fine, by reducing either or both.

(b) The governor shall not commute a sentence of life without possibility of parole.