dissenting.
I dissent to Division 5 of the majority opinion and to the judgment because I am opposed to reducing the standard of proof required of a convicted murderer who asserts mental retardation in an attempt to limit his punishment.
The majority holds that under Fleming v. Zant, 259 Ga. 687 (386 SE2d 339) (1989), a defendant who claims to be mentally retarded in a death-penalty sentencing hearing must only show that he is retarded by a preponderance of the evidence. The problem with the majority’s reasoning is that it conflicts with our statutory standards of proof for verdicts of insanity, and guilty but mentally retarded, and guilty but mentally ill. See OCGA § 17-7-131 and Spivey v. State, 253 Ga. 187 (319 SE2d 420) (1984).
This case deals with the sentencing phase of a death-penalty case. As such, the majority states that the purpose of the trial on the mental retardation issue is to give the defendant, “essentially the same opportunity to litigate the issue of his mental retardation as he would have had if the case were tried today, with the benefit of the OCGA § 17-7-131 (j) death-penalty exclusion.” Under OCGA § 17-7-131, the burden of persuasion of mental illness or mental retardation is on the defendant and must be proved beyond a reasonable doubt. OCGA § 17-7-131 (c) (3) provides:
*453The defendant may be found “guilty but mentally retarded” if the jury, or court acting as trier of facts, finds beyond a reasonable doubt that the defendant is guilty of the crime charged and is mentally retarded. . . ,1 [Emphasis supplied.]
The U. S. Supreme Court has approved provisions that a defendant must prove mental illness beyond a reasonable doubt, Patterson v. New York, 432 U. S. 197 (97 SC 2319, 53 LE2d 281) (1977), and that a state may require a criminal defendant to prove his insanity beyond a reasonable doubt. Rivera v. Delaware, 429 U. S. 877 (97 SC 226, 50 LE2d 160) (1976).
Mental retardation is a lesser debilitation than mental illness or insanity, and may be readily feigned. Stripling v. State, 261 Ga. 1 (401 SE2d 500) (1991). As pointed out in Stripling, supra, a defendant seeking to assert mental illness often attempts to “make himself appear more mentally ill than he probably is.” A preponderance of the evidence rule compounds the difficulty that sentencing juries face, requires triers of fact to make virtually impossible determinations, and opens the courts to a potential avalanche of appeals. Our courts will not only have to deal with habeas actions arising out of Fleming assertions, but they will also have to review the mental retardation trials on a case by case basis to determine the sufficiency of the evidence.
Finally, I must dissent to the Court’s interference with the legislative function. In Jones v. Swett, 244 Ga. 715, 717 (261 SE2d 610) (1979), we held:
Once the court interprets a statute, that interpretation becomes an integral part of the statute and any subsequent “reinterpretation” would be no different from a judicial alteration of language placed in the statute by the General Assembly itself. [Cits.]
In Spivey, supra, we interpreted OCGA § 17-7-131 to mean that mental illness and mental retardation must be proved by the defendant beyond a reasonable doubt. The legislature, at that time could have rewritten the statute if our holding misinterpreted its intent. It *454did not. By adopting a preponderance of the evidence standard here, under the guise of Fleming, supra, we preempt the function of the legislature and substitute the will of the Court for the will of the people as reflected by their elected representatives. I cannot agree.
Decided July 3, 1991 — Reconsideration denied July 24, 1991. Stephen F. Lanier, District Attorney, Michael J. Bowers, Attorney General, Susan V. Boleyn, Senior Assistant Attorney General, Paula K. Smith, Assistant Attorney General, Brinson, Askew & Berry, Robert M. Brinson, for The State and Zant. Stewart, Melvin & House, J. Douglas Stewart, Benna Kushlefsky, for Foster.Some commentators argue that the “beyond a reasonable doubt” standard applies only to the state’s proof of the crime, and not to the defendant’s proof of his claim of mental retardation. However, the state’s burden of proof in criminal matters is well known and it would serve no purpose to merely repeat that standard and exclude its application to the mental retardation claim. “It is a well settled canon of statutory construction that statutes are presumed to be enacted by the legislature with knowledge of the existing law.” Hart v. Owens-Illinois, 250 Ga. 397, 400 (297 SE2d 462) (1982). It is more plausible that the legislature would have specifically set out a preponderance of the evidence standard if it had so intended.