Nothing in sections 25-1140.09, 28-303, 28-313, and 29-2519 to 29-2546 shall be in any way deemed to repeal or limit existing procedures for automatic review of capital cases, nor shall they in any way limit the right of the Supreme Court to reduce a sentence of death to a sentence of life imprisonment in accordance with the provisions of section 29-2308, nor shall they limit the right of the Board of Pardons to commute any sentence of death to a sentence of life imprisonment.