concurring.
I join in Chief Justice Eagen’s opinion for the Court in this case. Because, however, the relationship of the instant decision to some of our other recent decisions may not be readily apparent, and because the problem of burdens of proof in “affirmative defense” situations and the problem of retroactivity and waiver in connection therewith present a rather treacherous area, I venture this supplementary statement of my own understanding.
The case at bar comes to us by way of an appeal from an order denying relief in a collateral proceeding under the Post Conviction Hearing Act. Act of January 25, 1966, P.L. (1965) 1580, 19 P.S. §§ 1180-1 et seq. (Supp.1977-78). The trial was in 1972 and the defense was self-defense. The defendant’s claim that he carried no burden of proof with respect to that defense was properly preserved at trial, but no appeal was taken because, one may assume, the trial court’s charge to the contrary was in accordance with the law of this Commonwealth as it then stood. As the Chief Justice’s opinion makes clear, that law has since been changed for us by the Supreme Court of the United States in Mullaney v. Wilbur, 421 U.S. 684, 95 S.Ct. 1881, 44 L.Ed.2d 508 (1975). The Supreme Court has also instructed that the new burden of proof with respect to the defense of self-defense is to be applied retrospectively. Hankerson v. North Carolina, 432 U.S. 233, 97 S.Ct. 2339, 53 L.Ed.2d 306 (1977).
*398In Commonwealth v. Ernst, 476 Pa. 102, 381 A.2d 1245 (1977), this Court, by an equal division, affirmed a murder conviction in which the defense was insanity. That issue was raised in the evidence, but the trial court’s charge stated that the burden was on the defendant to prove insanity by a preponderance of the evidence. This charge, too, was in accordance with settled Pennsylvania law at the time of trial,1 and no objection was taken to it by the defense. By the time the case came to this Court the law as to burden of proof as to insanity where that defense was in issue had been changed. See n. 1, supra. We nevertheless enforced our normal waiver rule because, contrary to our expectations, Patterson v. New York, 432 U.S. 197, 97 S.Ct. 2319, 53 L.Ed.2d 281 (1977), made it clear that the placement of burdens regarding the insanity defense were not matters of federal constitutional dimension unless some element of the crime in question is involved.2 To the same effect is Commonwealth v. Colbert, 476 Pa. 531, 383 A.2d 490 (1978), where the defense was intoxication. There was no objection to the placement of the burden of proof regarding intoxication of the defendant, and although the law on this issue changed after the case was tried (see Commonwealth v. Rose, 457 Pa. 380, 321 A.2d 880 (1974)), the question was nonconstitutional in nature and the waiver rule was enforced.
The circumstances of the case at bar are different. As Mr. Chief Justice Eagen notes, a majority of this Court is in *399agreement that the Constitution of the United States requires not only that the Commonwealth prove the absence of self-defense beyond a reasonable doubt when that issue is properly raised by the evidence in the case, but also that this requirement must be given retrospective effect. Opinion of the Court, ante at [slip opinion at 3 — 4]. See Commonwealth v. Hilbert, 476 Pa. 288, 382 A.2d 724 (1978). Since the retroactivity of the burden of proof holding with respect to self-defense has been settled for us by the United States Supreme Court, see Hilbert, supra; Hankerson v. North Carolina, supra, the remaining question is whether our state law waiver rules nevertheless bar a new trial. See Hanker-son, supra, at n. 8, 53 L.Ed.2d at 316 n. 8. In the context of the instant case, this question is also settled for us, this time by Pennsylvania’s Post-Conviction Hearing Act (the Act), supra.
Under Section 4(c) of the Act, 19 P.S. § 1180-4(c), a waiver of a claim which may be asserted under the Act occurs when a defendant fails to raise it on direct appeal, and this waiver is presumed to be “knowing and understanding.” See, e. g., Commonwealth v. Dancer, 460 Pa. 95, 331 A.2d 435 (1975). But by the terms of Section 4(c) itself, this presumption is rebuttable. If the post-conviction petitioner is able to show the existence of “extraordinary circumstances [justifying] his failure to raise the issue” at a prior opportunity, the issue is not waived. Section 4(b)(2) of the Act, 19 P.S. § 1186 — 4(b)(2). I agree with the Court that at the time of Lynch’s direct appeal the condition of the law of Pennsylvania relative to the burden of proof on the affirmative defense of self-defense was such that he should not be held to have “knowingly and understanding^” waived the burdens issue for purposes of the Act by failing to press the question on direct appeal.
Given the constitutional dimensions of the burden of proof issue which this case presents and our inability to find a valid waiver of that issue, the terms of the Act require that a new trial be granted to this appellant. Under Section 3(c)(12) of the Act, 19 P.S. § 1186-3(c)(12), Lynch is entitled *400to relief if there was an abridgement of a federal constitutional right “that was not recognized as existing at the time of trial [and] if the constitution requires retrospective application of that right.” See, e. g., Commonwealth v. Faison, 437 Pa. 432, 441-A3, 264 A.2d 394, 399 (1970); Commonwealth v. Hall, 447 Pa. 572, 287 A.2d 441 (1972); Commonwealth v. Pugh, 447 Pa. 582, 288 A.2d 519 (1972); Commonwealth v. Richardson, 433 Pa. 195, 203-04, 249 A.2d 307 (1969). Thus I agree with the Court that a basis for relief under the Act is made out in this case and that a new trial is required.
EAGEN, C. J., joins in this concurring opinion.. See, e. g., Commonwealth v. Zlatovich, 440 Pa. 388, 393, 269 A.2d 469 (1970), overruled in part in Commonwealth v. Demmitt, 456 Pa. 475, 321 A.2d 627 (1974).
. As the opinion in support of affirmance in Ernst pointed out, however, several defendants were accorded the benefit of our decision in Demmitt, supra, although their trials preceded the decision in Demmitt, because the issue of burden of proof relative to the affirmative defense had been preserved by a timely objection below. See, e. g., Commonwealth v. Moyer, 466 Pa. 464, 353 A.2d 447 (1976). But cf. Commonwealth v. Cain, 471 Pa. 140, 369 A.2d 1234 (1977) (opinions in support of affirmance) (preservation of objection to refusal to charge on voluntary manslaughter does not result in new trial, since subsequently announced right to such charge is not accorded retroactive effect).