[ First paragraph effective until August 2, 2012. For text effective August 2, 2012, see below.]

  Section 133B. In the case of every prisoner sentenced under the provisions of section twenty-five of chapter two hundred and seventy-nine except for those persons sentenced to a term of imprisonment as prescribed by the sentencing guidelines established by the sentencing commission, the parole board shall, within sixty days before the expiration of half of his maximum sentence, and thereafter at least once in each ensuing two-year period, consider carefully and thoroughly the merits of such case on the question of releasing such person on parole. After such consideration, the parole board may grant to such prisoner a parole permit to be at liberty upon such terms and conditions as it may prescribe for the unexpired term of his sentence. Such terms and conditions may be revised, altered and amended, and may be revoked by the parole board at any time. The violation by the holder of such permit of any of its terms or conditions, or of any law of the commonwealth, shall render such permit void, and thereupon, or if such permit has been revoked, the parole board may order his arrest and his return to prison, in accordance with the provisions of section one hundred and forty-nine. The period which must be served before such prisoner becomes eligible for parole shall be calculated with deductions applicable to other sentences for good conduct.

[ First paragraph as amended by 2012, 192, Sec. 40 effective August 2, 2012. For text effective until August 2, 2012, see above.]

  The parole board shall, within 60 days before the expiration of two-thirds of the maximum sentence of a prisoner sentenced under section 25 of chapter 279, and thereafter at least once in each ensuing 2-year period, consider carefully and thoroughly the merits of releasing such person on parole except for: (i) a habitual offender sentenced under subsection (b) of said section 25 of said chapter 279 or (ii) a prisoner sentenced to a term of imprisonment as prescribed by the sentencing guidelines established by the sentencing commission. After such consideration, the parole board may grant to such prisoner a parole permit to be at liberty upon such terms and conditions as it may prescribe for the unexpired term of his sentence. Such terms and conditions may be revised, altered and amended, and may be revoked by the parole board at any time. The violation by the holder of such permit of any of its terms or conditions, or of any law of the commonwealth, shall render such permit void, and thereupon, or if such permit has been revoked, the parole board may order his arrest and his return to prison, in accordance with the provisions of section one hundred and forty-nine. The period which must be served before such prisoner becomes eligible for parole shall be calculated with deductions applicable to other sentences for good conduct.

[ Paragraph added by 2012, 192, Sec. 41 effective August 2, 2012.]

  Habitual offenders sentenced under said subsection (b) of said section 25 of said chapter 279 shall not, except as provided under subsection (e) of said section 25 of said chapter 279, be eligible for parole, work release or furlough or receive any deduction from such person's sentence for good conduct.