Williams, C.J.
The issue in this case is whether, in a prosecution for second degree assault under RCW 9A.36-.020(l)(b), the State must disprove a defendant's claim of self-defense. The Court of Appeals held that the State need not do so, and affirmed petitioner's conviction. State v. [614]*614Acosta, 34 Wn. App. 387, 661 P.2d 602 (1983). We reverse the Court of Appeals and remand for a new trial.
Petitioner David Acosta met Kimberly Polmateer in a Portland bar on October 13, 1980. They later decided to drive to Vancouver in Polmateer's car. They parked in a dark alley and smoked some marijuana. Petitioner testified that while there he discovered that his wallet was missing, and accused Polmateer of taking it. He testified that when he threatened to go to the police she attacked him, scratching him and choking him with his tie. Polmateer's testimony contradicted petitioner's. She testified that petitioner attempted to rape and kill her and that she ran from the car to a nearby house. Although there were no other witnesses to the incident, several witnesses testified that when Polmateer arrived at the house she was in a hysterical state, beaten, bleeding, and unclothed from the waist down.
At his trial petitioner's attorney proposed a jury instruction which would have required the State to prove beyond a reasonable doubt that petitioner "was not acting in self-defense, or using lawful force as defined elsewhere in these instructions."1 Clerk's Papers, at 37. The trial court refused to give this instruction, and instead used WPIC 35.12, which lists the statutory elements of second degree assault. In addition, the court instructed the jury that
It is a complete defense to the charge of second degree assault that the defendant acted in self-defense.
[615]*615If you find from the evidence, and in accordance with these instructions that the defendant acted in self-defense, then it shall be your duty to return a verdict of not guilty.
Clerk's Papers, at 49. The trial court did not expressly inform the jury whether petitioner or the State bore the burden of proving or disproving self-defense. The jury found petitioner guilty.
I
The Burden of Proof
The due process clause of the fourteenth amendment to the United States Constitution requires the State to prove beyond a reasonable doubt all facts necessary to constitute the crime charged. Sandstrom v. Montana, 442 U.S. 510, 61 L. Ed. 2d 39, 99 S. Ct. 2450 (1979); In re Winship, 397 U.S. 358, 25 L. Ed. 2d 368, 90 S. Ct. 1068 (1970). There are two ways to determine whether absence of self-defense is an element or ingredient of the crime which the State must prove: (1) the statute may reflect a legislative intent to treat absence of self-defense as an element of the crime; or (2) proof of self-defense may negate an element of the crime. State v. McCullum, 98 Wn.2d 484, 490, 656 P.2d 1064 (1983); State v. Hanton, 94 Wn.2d 129, 132, 614 P.2d 1280, cert. denied, 449 U.S. 1035, 66 L. Ed. 2d 497, 101 S. Ct. 611 (1980).
The Washington Criminal Code is silent on whether the State must prove that a defendant did not act in self-defense. However, as we noted in State v. McCullum, supra at 492, the Legislature has clearly provided that a defendant must prove certain defenses by a preponderance of the evidence. See RCW 9A.12.010 (insanity); RCW 9A.32-.030(l)(c), .050(l)(b) (felony murder); RCW 9A.40.030 (kidnapping); RCW 9A.44.030 (sexual offenses); RCW 9A.48.060 (reckless burning); and RCW 9A.76.100 (compounding a crime). The Legislature's silence on the burden of proof of self-defense, in contrast to its specificity on these other defenses, is a strong indication that the Legis[616]*616lature did not intend to require a defendant to prove self-defense.
Even if the Legislature did intend to require the defendant to prove self-defense, this requirement will withstand constitutional scrutiny only if we determine that self-defense does not negate an essential element of the crime. McCullum, at 494; Hanton, at 132. To do so we must analyze each element of the crime charged. Hanton, at 132*. The defendant in this case was charged with and convicted of second degree assault, RCW 9A.36.020(l)(b). That statute provides that a person is guilty when he "[s]hall knowingly inflict grievous bodily harm". Because "knowingly" is expressly made an element of second degree assault, the prosecution must prove knowledge beyond a reasonable doubt. Knowledge is defined in RCW 9A.08.010, which provides in relevant part:
(b) Knowledge. A person knows or acts knowingly or with knowledge when:
(i) he is aware of a fact, facts, or circumstances or result described by a statute defining an offense; . . .
(Italics ours.)
Self-defense is defined by statute as a lawful act. See RCW 9A.16.020(3). It is therefore impossible for one who acts in self-defense to be aware of facts or circumstances "described by a statute defining an offense". RCW 9A.08-.010(l)(b)(i). This is just another way of stating that proof of self-defense negates the knowledge element of second degree assault. Since proof of self-defense negates knowledge, due process and our prior cases require us to hold that the State must disprove self-defense in order to prove that the defendant acted unlawfully.2
[617]*617We reached a similar result in McCullum. The issue in McCullum was whether the State in a first degree murder case must disprove self-defense when the issue is properly raised. There we noted that the statutory definition of intent requires that the defendant act "with the objective or purpose to accomplish a result which constitutes a crime", RCW 9A.08.010(l)(a), that is, that the defendant act "unlawfully". See McCullum, at 495. Since a person acting in self-defense acts lawfully, we held that self-defense negates intent, and that the State therefore must disprove self-defense when the issue is properly raised.
Similarly, in Hanton, we held that evidence of self-defense negated the element of "recklessness" in the first degree manslaughter statute, RCW 9A.32.060(l)(a). There we focused upon the requirement of wrongful action in the definition of recklessness. RCW 9A.08.010(l)(c) provides:
(c) Recklessness. A person is reckless or acts recklessly when he knows of and disregards a substantial risk that a wrongful act may occur . . .
We held in Hanton, at page 133:
[618]*618There can be no recklessness without disregard of risk of a wrongful act, and self-defense, as defined, is not "wrongful."
Given our decisions in McCullum and Hanton, consistency dictates that the State bear the burden of disproving self-defense where the applicable mental state is knowledge. RCW 9A.08.010 establishes a hierarchy of culpable mental states, ranging from intent to criminal negligence. Proof of a higher mental state is necessarily proof of a lower mental state. RCW 9A.08.010(2). We believe that we are required to treat the effect of self-defense on each mental state in a consistent manner. Consider a case in which the defendant is charged with a crime requiring proof of intent and in which the jury was instructed on one lesser offense requiring proof of knowledge and another requiring proof of recklessness. Were we to hold that the defendant bore the burden of proof in knowledge crimes, the jury instruction on the burden of proof would be unbearably complicated, with the burden shifting from the State, to the defendant, and back again.
Finally, our holding today is consistent with the longstanding rule in Washington that a criminal assault requires unlawful force. See Howell v. Winters, 58 Wash. 436, 108 P. 1077 (1910) (civil assault); Peasley v. Puget Sound Tug & Barge Co., 13 Wn.2d 485, 125 P.2d 681 (1942) (civil assault); State v. Rush, 14 Wn.2d 138, 127 P.2d 411 (1942); State v. Stewart, 73 Wn.2d 701, 440 P.2d 815 (1968). In Rush, the court noted that the statute on second degree assault prohibited willful "assault", but that the statute did not define "assault". In the absence of a statutory definition the court resorted to the common law rule reflected in Howell and Peasley and stated: "We are committed to the rule that an assault is an attempt, with unlawful force, to inflict bodily injury upon another ..." (Italics ours.) Rush, at 139. If we were to hold that the defendant bore the burden of proving self-defense, we would be relieving the State of its obligation to prove that the defendant's use of force was unlawful. Therefore, con[619]*619sistent with our prior cases, we hold that in a second degree assault prosecution the State must disprove self-defense beyond a reasonable doubt. State v. LeBlanc, 34 Wn. App. 306, 660 P.2d 1142, review denied, 100 Wn.2d 1021 (1983).
II
Jury Instructions
The next issue is whether the trial court erred in failing to inform the jury that the State bears the burden of disproving self-defense. In State v. McCullum, supra, we stated that when some evidence of self-defense is presented, the jury "should be instructed that the State bears the burden of proving the absence of self-defense beyond a reasonable doubt." McCullum, at 500. Our discussion of jury instructions in McCullum has caused some disagreement and confusion in the Court of Appeals; the principal area of disagreement is whether the "rule" in McCullum is retroactive, that is, whether it applies to cases tried before McCullum was decided. See, e.g., State v. Takacs, 35 Wn. App. 914, 671 P.2d 263 (1983) (Division One) (discussion of jury instructions in McCullum prospective only; one judge dissenting); State v. Mercer, 34 Wn. App. 654, 663 P.2d 857 (1983) (Division One) (discussion of jury instructions in McCullum prospective only); State v. Heath, 35 Wn. App. 269, 666 P.2d 922 (1983) (Division Three) (discussion of jury instructions in McCullum not prospective only); State v. LeBlanc, 34 Wn. App. 306, 660 P.2d 1142 (1983) (Division Three) (discussion of jury instructions in McCullum not prospective only). We take this opportunity to clarify what was said in McCullum. To do so it is necessary to review the cases decided before McCullum that discussed the need for and the content of jury instructions regarding the burden of proof of self-defense.
In State v. Roberts, 88 Wn.2d 337, 562 P.2d 1259 (1977), this court reversed the petitioner's conviction for reasons not relevant to this opinion. The court discussed in detail, however, what jury instructions should be given at the petitioner's trial on remand. We stated that when evidence [620]*620of self-defense is presented, the jury should be "simply informed that the State has the burden to prove absence of self-defense beyond a reasonable doubt." Roberts, at 346. The opinion did not state whether failure to so instruct would be reversible error; it merely stated that the instructions "should be" given on remand.
In State v. King, 92 Wn.2d 541, 599 P.2d 522 (1979), the issue was whether the failure to instruct specifically on the burden of proof of self-defense was reversible error. The trial court had instructed the jury that to convict the petitioner, it must find beyond a reasonable doubt that the killing was not "either excusable or justifiable". King, at 544. The court also had instructed that a killing done in self-defense was justifiable. King, at 544. This court held that these instructions, when read together, adequately allocated the burden of proof to the State; under these circumstances a specific instruction allocating the burden was unnecessary. See King, at 546.
We employed a similar analysis in State v. Hanton, 94 Wn.2d 129, 614 P.2d 1280, cert. denied, 449 U.S. 1035, 66 L. Ed. 2d 497, 101 S. Ct. 611 (1980). There we reversed petitioner's conviction because the trial court had instructed the jury that the defendant bore some burden of proving self-defense. Hanton, at 131. We also stated that on remand, the trial court need not give a separate instruction specifically informing the jury that the State bore the burden of proof on self-defense. Hanton, at 134. We reasoned that the jury could infer from the definitions of recklessness and self-defense that the burden of disproving self-defense was on the State.
Finally, in State v. Savage, 94 Wn.2d 569, 618 P.2d 82 (1980), we again considered whether failure to instruct specifically on the burden of proof constituted reversible error. In Savage, as in King, the jury was instructed that to find the petitioner guilty of second degree murder, it must find that the killing was not justifiable or excusable. Savage, at 581. The jury was also instructed that a killing done in self-defense was justifiable. As in King, we held that under [621]*621these circumstances the failure to allocate specifically the burden of proof was not error. The analysis in Savage differed slightly from King, however. Whereas in King we said that the instructions did allocate the burden to the State, in Savage we said that the instructions "allowed the defendant to argue to the jury that the State bore the burden of proving absence of self-defense." Compare Savage, at 582, with King, at 546.
We reconsidered these cases in State v. McCullum, 98 Wn.2d 484, 656 P.2d 1064 (1983). There we gave guidelines to be used by the trial court on petitioner McCullum's new trial and by other courts in "future cases". McCullum, at 498. We stated that failure to give an instruction that expressly allocates the burden of proof to the State will not necessarily be reversible error, but that giving such an instruction would be "preferable in order to avoid any confusion by the jury on burdens of proof." (Citation omitted.) McCullum, at 499. We relied primarily on United States v. Corrigan, 548 F.2d 879 (10th Cir. 1977). In that case the court stated:
[T]he importance of avoiding any confusion concerning the burden of proof on [self-defense] is apparent. The inclusion of a specific statement of the burden of proof in the defense instruction is preferable. Its omission, however, is not reversible error per se. The question is whether the instructions, taken as a whole, adequately informed the jury that prosecution's burden of proof beyond a reasonable doubt applied to defendant's [self-defense claim].
(Italics ours.) Corrigan, at 882. This is what was meant in McCullum-, a specific instruction is preferable, but failure to provide one is not reversible per se so long as the instructions, taken as a whole, make it clear that the State has the burden. We adhere to this reasoning. The jury should be informed in some unambiguous way that the State must prove absence of self-defense beyond a reasonable doubt. The defendant is entitled to a correct statement of the law, and should not be forced "to argue to the jury that the State [bears] the burden of proving absence of [622]*622self-defense." (Italics ours.) Savage, at 582. Rather, the defense attorney is only required to argue to the jury that the facts fit the law; the attorney should not have to convince the jury what the law is. Thus, contrary to what was said in Hanton, we now believe that the better practice is simply to give a separate instruction clearly informing the jury that the State has the burden of proving the absence of self-defense beyond a reasonable doubt. See Roberts, at 346.
From the above discussion it should be clear that McCullum was not intended to be a decision in which retroactivity was at issue. The question in each case is whether the trial court committed error in its instructions to the jury. In resolving this question, the test is whether the jury was informed, or could understand from the instructions as a whole, that the State bears the burden of proof on self-defense. In this respect McCullum is not a drastic departure from King or Hanton. The real import of McCullum was to express our strong preference for clear and unambiguous instructions on the burden of proof, so that the issue of the adequacy of instructions would arise less frequently.
With the above analysis in mind we turn to the instructions in this case. As noted above, the trial court instructed that "to convict" the defendant, the jury must find (1) that the defendant "knowingly assaulted" the victim; (2) that the acts occurred in Clark County; and either (3) that the assault was committed with intent to rape, or (4) that the defendant "knowingly inflicted grievous bodily harm". Clerk's Papers, at 49. The court further instructed the jury that the State must prove beyond a reasonable doubt elements 1 and 2, and either element 3 or 4. Immediately following this, the court instructed:
It is a complete defense to the charge of second degree assault that the defendant acted in self-defense.
If you find from the evidence, and in accordance with these instructions that the defendant acted in self-[623]*623defense, then it shall be your duty to return a verdict of not guilty.
Clerk's Papers, at 49.
We believe that these instructions, when read together, did not adequately inform the jury that the State must prove absence of self-defense. Unlike Hanton, King, and Savage, the jury was not told in the "to convict" instruction that the force used must be unlawful, wrongful, or without justification or excuse. In addition, from the placement of the self-defense instruction immediately after the instruction listing the elements that must be proved by the State, the jury could have believed by negative inference that the State had no burden with respect to self-defense.
Other state courts have reached similar conclusions. In State v. McNulty, 60 Hawaii 259, 264, 588 P.2d 438 (1978), the court stated:
In failing to specifically allocate the burden of disproving self-defense to the state, the instructions could have permitted the jury to believe that the appellant, having raised the issue of justification, was obligated to prove it.
The Supreme Judicial Court of Massachusetts similarly held an instruction informing the jury that it must convict the defendant, "[ujnless you find" that the defendant acted in self-defense, affirmatively placed the burden of proof on the defendant. Connolly v. Commonwealth, 377 Mass. 527, 387 N.E.2d 519, 523 (1979). See also Berrier v. Egeler, 583 F.2d 515, 517 (6th Cir.), cert. denied, 439 U.S. 955, 58 L. Ed. 2d 347, 99 S. Ct. 354 (1978) (failure to allocate burden to the State "implies that the defendant must prove his claim of self-defense"); State v. Torres, 619 P.2d 694, 695 (Utah 1980) (failure to instruct "that the defendant need not prove his defense" is reversible error).
A reasonable juror could have mistakenly believed that the State need not disprove self-defense, and that the defendant bore some burden of proof on this issue. The trial court's failure to inform the jury of the State's burden was therefore error.
[624]*624It remains to be determined whether the error was harmless. As we noted in State v. Johnson, 100 Wn.2d 607, 674 P.2d 145 (1983), the United States Supreme Court has not decided whether instructional errors of the sort here can ever be considered harmless. See Connecticut v. Johnson, 460 U.S. 73, 74 L. Ed. 2d 823, 103 S. Ct. 969 (1983) (four Justices concluding that error is harmless only when element of crime is not disputed; four Justices concluding that error may be harmless under the overwhelming evidence test). In State v. Johnson, supra, we also noted that this court and the United States Supreme Court "have vacillated between two alternative approaches: (1) constitutional error is harmless only if it can be said beyond a reasonable doubt that it did not contribute to the verdict (hereinafter 'contribution test'); and (2) constitutional error is harmless whenever it can be said beyond a reasonable doubt that the evidence not tainted by the error is so overwhelming that it necessarily leads to a finding of guilt (hereinafter 'overwhelming evidence test')." Johnson, at 621. We declined to choose between these two approaches in Johnson because we found the errors harmless under either test.
In this case, we also decline to choose between the contribution test and the overwhelming evidence test, because under either test the error cannot be considered harmless. The jury could have believed the defendant had to persuade them that he acted in self-defense. We cannot say beyond a reasonable doubt that this confusion did not "contribute" to the jury's verdict. Similarly, we cannot say beyond a reasonable doubt that, absent the erroneous instruction, the jury would necessarily have returned a guilty verdict. The crucial issue in this case was self-defense. Both the State and the defense presented some evidence to support their version of the events in question. Although petitioner's self-defense claim may appear doubtful in this case, this court will not substitute its judgment for that of the jury on factual matters. We therefore cannot say that the instructional error was harmless beyond [625]*625a reasonable doubt.
We reverse petitioner's conviction and remand for a new trial. On remand the jury should be instructed on the definition and elements of self-defense. The jury then should be instructed that the State bears the burden of proving the absence of self-defense beyond a reasonable doubt. Finally, since we hold that self-defense is inconsistent with one of the statutory elements of assault, the jury should be instructed that the State sustains its burden if it proves beyond a reasonable doubt each of the elements of the crime as defined by the statute. State v. McCullum, 98 Wn.2d 484, 500-01, 656 P.2d 1064 (1983).
Rosellini, Stafford, Utter, and Pearson, JJ., concur.