Subject to the provisions of sections 19-2515 and 19-2515A, Idaho Code, every person guilty of murder of the first degree shall be punished by death or by imprisonment for life, provided that a sentence of death shall not be imposed unless the prosecuting attorney filed written notice of intent to seek the death penalty as required under the provisions of section 18-4004A, Idaho Code, and provided further that whenever the death penalty is not imposed the court shall impose a sentence. If a jury, or the court if a jury is waived, finds a statutory aggravating circumstance beyond a reasonable doubt but finds that the imposition of the death penalty would be unjust, the court shall impose a fixed life sentence. If a jury, or the court if a jury is waived, does not find a statutory aggravating circumstance beyond a reasonable doubt or if the death penalty is not sought, the court shall impose a life sentence with a minimum period of confinement of not less than ten (10) years during which period of confinement the offender shall not be eligible for parole or discharge or credit or reduction of sentence for good conduct, except for meritorious service. Every person guilty of murder of the second degree is punishable by imprisonment not less than ten (10) years and the imprisonment may extend to life.