The United States Supreme Court (USSC), in Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002), held the execution of a mentally retarded person is cruel and unusual punishment prohibited by the Eighth Amendment of the United States Constitution. The USSC noted that “[t]o the extent there is serious disagreement about the execution of mentally retarded offenders, it is in determining which offenders are in fact retarded.... Not all people who claim to be mentally retarded will be so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus.” Id. at 317, 122 S.Ct. at 2250. The USSC left “the task of developing appropriate ways to enforce the constitutional restrictions upon [the] execution of sentences” to the states. Id. Therefore, the state of South Carolina has the obligation to establish procedures for possible capital cases where the defendant is allegedly mentally retarded.
Petitioners, all either death-sentenced inmates or capital defendants, filed this petition for a writ of certiorari in our original jurisdiction requesting we establish procedures implementing the Atkins decision.1
ISSUES
I. What is the definition of mental retardation?
II. What is the procedure for making the mental retardation determination in post-Atkins cases?
III. What is the procedure for cases where the defendant was sentenced to death prior to Atkins ?
DISCUSSION
I
We find it inappropriate to create a definition of mental retardation different from the one already established by the legislature in S.C.Code Ann. § 16-3-20(C)(b)(10) (2003) (mental retardation is a statutory mitigating circumstance).2 *279Section 16-3-20(C)(b)(10) defines mental retardation as: “significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior and manifested during the developmental period.” Altering this definition is a matter for the legislature.
II
Regarding the procedures to be used in making the mental retardation determination in post -Atkins cases, we conclude the trial judge shall make the determination in a pretrial hearing, if so requested by the defendant or the prosecution, after hearing evidence, including expert testimony, from both the defendant and the State. The defendant shall have the burden of proving he or she is mentally retarded by a preponderance of the evidence. Cf. State v. Reed, 332 S.C. 35, 503 S.E.2d 747 (1998)3 (defendant bears burden of proving incompetence by preponderance of evidence); State v. Kelly, 331 S.C. 132, 502 S.E.2d 99 (1998)4 (same).
If the judge finds the defendant to be mentally retarded by a preponderance of the evidence in the pre-trial hearing, the defendant will not be eligible for the death penalty. If, however, the judge finds the defendant is not mentally retarded and the jury finds the defendant guilty of the capital charge, the defendant may still present mitigating evidence that he or she had mental retardation at the time of the crime. See S.C.Code Ann. § 16-3-20(C)(b)(10) (2003).5 If the jury finds this mitigating circumstance, then a death sentence will not be imposed.
Ill
While petitioners argue we should establish procedures for eases where the defendant was sentenced to death prior to *280Atkins,6 such procedures already exist.
A death row inmate who claims he is mentally retarded and, as a result, not subject to the death penalty, may institute post-conviction relief (PCR) proceedings because his sentence is in violation of the Constitution and exceeds the maximum authorized by law.7 See S.C.Code Ann. §§ 17-27-20(a) and - 160 (2003). As with other PCR claims, the applicant must show he or she is mentally retarded by a preponderance of the evidence. See, e.g., Singleton v. State, 313 S.C. 75, 437 S.E.2d 53 (1993) (competency for execution). If mental retardation is proven, the PCR court will vacate the death sentence and impose a life sentence.
JEAN H. TOAL, C.J., JAMES E. MOORE, JOHN H. WALLER, JR., E.C. BURNETT, III, and COSTA M. PLEICONES, JJ.