“(d)(3)a. Not later than ninety days before trial the defendant may file a motion with the Court alleging that he was seriously mentally retarded at the time the crime was committed. Upon the filing of the motion, the Court shall order an evaluation of the defendant for the purpose of providing evidence of the following:
1. Whether the defendant has a significantly subaverage level of intellectual functioning;
2. Whether the defendant’s adaptive behavior is substantially impaired; and,
3. Whether the conditions described in subparagraphs (1) and (2) of this paragraph existed before the defendant became 18 years of age.
b. During the hearing authorized by subsections (b) and (c) of this section, the defendant and the State may present relevant and admissible evidence on the issue of the defendant’s alleged mental retardation, or in rebuttal thereof. The defendant shall have the burden of proof to demonstrate by clear and convincing evidence that the defendant was seriously mentally retarded at the time of the offense. Evidence presented during the hearing shall be considered by the jury in making its recommendation to the Court pursuant to subsection (c)(3) of this section as to whether the aggravating circumstances found to exist outweigh the mitigating circumstances found to exist. The jury shall not make any recommendation to the Court on the question of whether the defendant was seriously mentally retarded at the time the crime was committed.
c. If the defendant files a motion pursuant to this paragraph claiming serious mental retardation at the time the crime was committed, the Court, in determining the sentence to be imposed, shall make specific findings as to the existence of serious mental retardation at the time the crime was committed. If the Court finds that the defendant has established by clear and convincing evidence that he was seriously mentally retarded at the time the crime was committed, notwithstanding any other provision of this section to the contrary the Court shall impose a sentence of imprisonment for the remainder of the defendant’s natural life without benefit of probation or parole or any other reduction. If the Court determines that the defendant has failed to establish by clear and convincing evidence that he was seriously mentally retarded at the time the crime was committed, the Court shall proceed to determine the sentence to be imposed pursuant to the provisions of this subsection. Evidence on the question of the defendant’s mental retardation presented during the hearing shall be considered by the Court in its determination pursuant to this section as to whether the aggravating circumstances found to exist outweigh the mitigating circumstances found to exist.
d. When used in this paragraph:
1. ‘Seriously mentally retarded’ or ‘serious mental retardation’ means that an individual has significantly subaverage intellectual functioning that exists concurrently with substantial deficits in adaptive behavior and both the significantly subaverage intellectual functioning and the deficits in adaptive behavior were manifested before the individual became 18 years of age;
2. ‘Significantly subaverage intellectual functioning’ means an intelligent quotient of 70 or below obtained by assessment with one or more of the standardized, individually administered general intelligence tests developed for the purpose of assessing intellectual functioning;
3. ‘Adaptive behavior’ means the effectiveness or degree to which the individual meets the standards of personal independence expected of the individual’s age group, sociocultural background, and community setting, as evidenced by significant limitations in not less than two of the following adaptive skill areas: communication, self-care, home living, social skills, use of community resources, self-direction, functional academic skills, work, leisure, health or safety.”
Section 2. This Act shall apply to all defendants tried, re-tried, sentenced or re-sentenced after its effective date.
Section 3. The prohibition against the imposition of or execution of a death sentence upon a seriously mentally retarded person, the standards of proof, and the definitions of “seriously mentally retarded”, “significantly subaverage intellectual functioning”, and “adaptive behavior” as set forth in this Act shall be applicable in all judicial or executive proceedings relating to any persons currently under a sentence of death that was imposed prior to the effective date of this Act.
Section 4. If any provision of this Act or the application thereof to any person or circumstance is held invalid, such invalidity shall not affect other provisions or applications of the Act which can be given effect without the invalid provision or application, and to that end the provisions of this Act are declared to severable.