The Director, with the consent of the Governor, may allow to any prisoner confined in a state correctional facility a credit toward his term of confinement if he (i) renders assistance in preventing the escape of another prisoner or in the apprehension of an escaped prisoner; (ii) gives a blood donation to another prisoner; (iii) voluntarily or at the instance of a prison official renders other extraordinary services; or (iv) suffers bodily injury while in the prison system. The Director shall determine the amount of any such credit for each such service or injury. In unusual circumstances a prisoner may receive credit for donating blood, under regulations prescribed by the Director, to blood banks licensed by or subject to regulations of the State Board of Health. The Director may allow the credit permitted by this section to a prisoner who has been sentenced to the Department of Corrections but who is confined in a local correctional facility. Except as provided hereafter, any credit allowed under the provisions of this section shall be applied as provided in § 53.1-199. A prisoner who has been sentenced to a term of life imprisonment or to two or more life sentences shall be eligible for credits allowed under the provisions of this section. One-half of such credit shall be applied to reduce the period of time such prisoner shall serve before being eligible for parole. Credits allowed under the provisions of this section may not be forfeited under § 53.1-189. Credits shall not be allowed under the provisions of this section to apply toward a term of confinement imposed upon a conviction of a felony offense committed on or after January 1, 1995.