¶ 1. This case presents a constitutional challenge to the statute making it a crime to engage in repeated acts of sexual assault of the same child, Wis. Stat. § 948.025 (1997-98).1 The defendant challenges the provision in the statute that relieves the jury of any requirement of unanimity as to the specific individual acts of sexual assault that combine to constitute the crime, as long as it unanimously agrees that the defendant committed the minimum number required, to wit, at least three.
¶ 2. The statute previously survived a unanimity challenge under the state constitution in State v. Molitor, 210 Wis. 2d 415, 565 N.W.2d 248 (Ct. App. 1997). In Molitor, the court of appeals concluded that the statute's requirement of jury unanimity on the existence of a continuing course of sexually assaultive conduct satisfied the defendant's right to a unanimous verdict, even though unanimity is not required as to each discrete act of sexual assault comprising the course of conduct. Then came Richardson v. United States, 526 U.S. 813 (1999), in which the United States Supreme Court held that to convict a defendant under the federal "continuing criminal enterprise" drug statute, the jury must unanimously agree on the specific underlying drug code violations that comprise the "continuing criminal enterprise". Id. at 815.
*369¶ 3. After Molitor but before Richardson, the defendant in this case, William G. Johnson, was convicted under Wis. Stat. § 948.025 for repeated sexual assault of the same child, after a trial in which the state introduced evidence of more than three separate acts of sexual assault against the same victim. On post-conviction motion and appeal, Johnson argued that Molitor cannot survive Richardson, and since the jury in his case had not been instructed that it must be unanimous on the specific predicate acts of sexual assault that comprised the crime, his right to a unanimous verdict had been violated. The court of appeals certified the case to us.2 We conclude that Molitor survives Richardson, and under the state and federal constitutional analyses in both cases,, the statute is constitutional. Accordingly, we affirm the circuit court's denial of the motion for a new trial.
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¶ 4. Johnson was charged with repeated sexual assault of the same child in violation of Wis. Stat. § 948.025 arising out of a series of incidents involving Roshunda R., who was 14 years old when the incidents *370occurred.3 At trial, Roshunda testified that she used to live across the street from Johnson's girlfriend and that she would sometimes play with his girlfriend's children. Roshunda testified that during the summer of 1997, Johnson touched her sexually a number of times. The first of these sexual contacts occurred on a day in July 1997, when a person Roshunda knew as "Marianne" got in trouble with the police; a detective's testimony determined this date to be July 8, 1997. Roshunda was on Johnson's porch that evening with a number of other people, and Johnson touched her chest over her clothes. When she moved to a different spot on the porch, Johnson followed her and touched her again on her chest and "butt."
¶ 5. Roshunda also testified about a separate incident that occurred later that summer, on a day when her family returned to Kenosha from Waukegan, Illinois, where they were living at the time. Roshunda's mother established this date as August 21, 1997. Roshunda testified that while she and her sister were visiting at Johnson's house on that day, Johnson touched her on her breast and "bottom." When she tried to leave the house, Johnson asked her for a hug and a kiss and then hit her "bottom" as she was going out the door.
¶ 6. Roshunda also testified about a game of tag that occurred sometime in July 1997. She said that during the game of tag, Johnson caught her from behind and touched her chest, "butt," and vagina.
¶ 7. At the conclusion of the trial, the Kenosha County Circuit Court, the Honorable Michael S. *371Fisher, instructed the jury on the elements of the crime of repeated sexual assault of the same child:
Before you may find the defendant guilty of this offense, the State must prove by evidence which satisfied you beyond a reasonable doubt, that the following three elements were present.
The first element requires that the defendant committed three or more sexual assaults of Roshunda. In this case, the sexual assaults are alleged to have involved sexual contact.
The second element requires that Roshunda had not attained the age of 16 years at the time of each act of sexual contact.
The third element requires that at least three of the alleged sexual assaults took place from a specific period of time. The specific period of time is from July 1,1997 through August 21,1997.
¶ 8. This instruction derives from the pattern jury instruction applicable to this crime. See Wis JI — Criminal 2107. However, the circuit court did not read the entire instruction to the jury, but, rather, omitted the part of the instruction recommended for use in cases in which evidence of more than three acts of sexual assault has been admitted. That section of the pattern instruction paraphrases Wis. Stat. § 948.025(2) and tells the jury: "Before you may find the defendant guilty, you must unanimously agree that at least three sexual assaults occurred. . .but you need not agree on which acts constitute the required three." Johnson was convicted and sentenced to ten years in prison.
¶ 9. Johnson moved for a new trial, arguing that his right to a unanimous verdict had been violated *372because the State introduced evidence of more than the minimum number of sexual assaults required to constitute the crime, but the jury was not instructed that it had to agree unanimously on the specific acts of sexual assault before convicting him. Johnson argued that Richardson, decided after his trial, called into question the constitutionality of Wis. Stat. § 948.025 because the statute specifically allows conviction in the absence of jury unanimity on thé individual acts of sexual assault that make up the crime. The circuit court denied the postconviction motion, concluding that Richardson was distinguishable from Molitor. Johnson appealed, and the court of appeals certified the case to us.
HH W
¶ 10. The constitutionality of a statute is a question of law that this court reviews without deference to the lower courts. State v. Randall, 192 Wis. 2d 800, 824, 532 N.W.2d 94 (1995). Statutes are presumed to be constitutional. Gloria A. v. State, 195 Wis. 2d 268, 276, 536 N.W.2d 396 (Ct. App. 1995). A statute will not be invalidated unless it has been proven unconstitutional beyond a reasonable doubt. Bachowski v. Salamone, 139 Wis. 2d 397, 404, 407 N.W.2d 533 (1987). The party challenging a statute's constitutionality bears the burden of overcoming the strong presumption in favor of the statute's validity. State v. Borrell, 167 Wis. 2d 749, 762, 482 N.W.2d 883, 887 (1992).
¶ 11. The Wisconsin Constitution's guarantee of the right to trial by jury includes the right to a unanimous verdict with respect to the ultimate issue of guilt *373or innocence. Wis. Const., art. I, §§ 5 4 and 7;5 State v. Derango, 2000 WI 89, ¶ 13, 236 Wis. 2d 721, 731, 613 N.W.2d 833. To say that the jury must be unanimous, however, does not explain what the jury must be unanimous about. For this we look to the statutory language defining the crime and its elements. "The principal justification for the unanimity requirement is that it ensures that each juror is convinced beyond a reasonable doubt that the prosecution has proved each essential element of the offense." Derango at ¶ 13 (quoting State v. Lomagro, 113 Wis. 2d 582, 591, 335 N.W.2d 583 (1983)). Thus, while jury unanimity is required on the essential elements of the offense, when the statute in question establishes different modes or means by which the offense may be committed, unanimity is generally not required on the alternate modes or means of commission. Derango, 2000 WI at ¶¶ 13-14.
*374¶ 12. Ordinarily, then, the first step in a unanimity challenge is an examination of the language of the statute in order to determine the elements of the crime and whether the legislature has created a single offense with multiple or alternate modes of commission. Derango, 2000 WI at ¶ 14. "The point is to determine legislative intent: did the legislature intend to create multiple, separate offenses, or a single offense capable of being committed in several different ways?" Id. at ¶ 15. For example, where the legislature has specified that any of several different mental states will satisfy the intent or mens rea element of a particular crime, unanimity is not required on the specific alternate mental state as long as the jury unanimously agrees that the state has proven the intent element beyond a reasonable doubt. Id. at ¶¶ 23-25.
¶ 13. Federal constitutional due process considerations, however, limit the state's ability to define a crime so as to dispense with the requirement of jury unanimity on the alternate means or modes of committing it. Richardson, 526 U.S. at 820 (citing Schad v. Arizona, 501 U.S. 624, 632-33 (1991) (plurality opinion) and Id. at 651 (Scalia, J., concurring); Derango, 2000 WI at ¶ 22 (citing Schad, 501 U.S. at 635). So the second step in the analysis is an evaluation of whether the lack of jury unanimity on the alternate means or modes of commission violates due process. Derango, 2000 WI at ¶ 22. This involves an inquiry into the fundamental fairness and rationality of the legislative choice, starting, however, with a presumption that the legislature has made its determination fairly and rationally. Id. As we noted in Derango, the due process fundamental fairness and rationality test for unanim*375ity challenges was established by the Supreme Court in Schad and focuses on historical practice and the relative moral and conceptual equivalence of the alternate modes or means of committing the crime. Id.
¶ 14. The statute in question here does not present a difficult issue of statutory interpretation. The language of Wis. Stat. § 948.025 is unambiguous as to the elements of the offense and the question of what the jury must be unanimous about before convicting a defendant of repeated sexual assault of the same child:
948.025 Engaging in repeated acts of sexual assault of the same child. (1) Whoever commits 3 or more violations under s. 948.02(1) or (2) [first and second degree sexual assault of a child] within a specified period of time involving the same child is guilty of a Class B felony.
(2) If an action under sub. (1) is tried to a jury, in order to find the defendant guilty the members of the jury must unanimously agree that at least 3 violations occurred within the time period applicable under sub. (1) but need not agree on which acts constitute the requisite number.
¶ 15. It is clear from this language that the predicate acts of sexual assault are not themselves elements of the offense, about which the jury must be unanimous before convicting the defendant. Rather, to convict under this statute, the jury need only unanimously agree that the defendant committed at least three acts of sexual assault of the same child within the specified time period. Where evidence of more than three acts is admitted, the jury need not unanimously agree about the underlying acts as long as it unanimously agrees that the defendant committed at least three.
¶ 16. In other words, it is the course of sexually assaultive conduct that constitutes the primary ele*376ment of this offense, about which the jury must be unanimous (the second and third elements are the age of the victim and the timing of the acts). See Wis JI — Criminal 2107. Unanimity is explicitly not required regarding the individual acts of sexual assault.
¶ 17. This brings us to the question of whether dispensing with unanimity on the predicate acts that comprise the course of conduct element of this offense is consistent with federal due process under Derango and Schad. This also is not a difficult question. This statute was enacted in 1993, and, therefore, like the statute at issue in Derango, "does not have a lengthy history to look to as an indicia of what is acceptable as fundamentally fair; but Schad recognized that this might often be the case with modern criminal statutes." Derango, 236 Wis. 2d at 738 (citing Schad, 501 U.S. at 640, n. 7). Nevertheless, Wisconsin has historically held that in "continuing course of conduct" crimes, the requirement of jury unanimity is satisfied even where the jury is not required to be unanimous about which specific underlying act or acts constitute the crime. See Lomagro, 113 Wis. 2d at 589; State v. Giwosky, 109 Wis. 2d 446, 451, 326 N.W.2d 232 (1982).
¶ 18. Furthermore, the predicate acts of first- and second-degree sexual assault that combine to establish the required course of conduct under Wis. Stat. § 948.025 are basically morally and conceptually equivalent. There is, of course, a distinction in victim age and maximum penalty as between first- and second-degree sexual assault of a child: the former involves victims under age 13 and carries a 40-year confinement maximum; the latter involves victims under age 16 and carries a 20-year confinement maxi*377mum. See Wis. Stat. § 948.02(1) and (2). And different types of sexual conduct — from sexual intercourse to various forms of sexual contact — can be implicated in either offense. See Wis. Stat. §§ 948.02(1) and (2), 948.01(5) and (6). But these variations are not of such a degree or nature as to call into question the basic moral and conceptual equivalence of first- and second-degree sexual assault of a child. Lack of jury unanimity regarding the specific acts constituting the required minimum of three raises no concern about fundamental fairness under these circumstances.
¶ 19. After all, the violations of the law about which the jury need not be unanimous under this statutory scheme all involve the sexual abuse of children, crimes of the same or similar nature and level of culpability. It is therefore not unfair or irrational to lift the requirement of jury unanimity as to the specific underlying acts as long as unanimity is required regarding the existence of the course of conduct, defined as at least three acts of sexual assault of the same child.
¶ 20. This is essentially the same conclusion the court of appeals reached in Molitor, although it did not engage in the Schad due process analysis as we have just done. In Molitor, the defendant was charged under Wis. Stat. § 948.025 with engaging in sexual intercourse with a 15-year-old girl "on more than three occasions between April 1 and May 21, 1995." Molitor, 210 Wis. 2d at 418. Molitor pleaded no contest to the charge and was sentenced to a 20-year prison term.
¶ 21. On appeal, Molitor attacked the constitutionality of Wis. Stat. § 948.025 on unanimity grounds. The court of appeals rejected the defendant's argument and upheld the statute, citing our "continuing course of conduct" cases, Giwosky and Lomagro:
*378The supreme court in State v. Giwosky concluded that when the charged behavior constitutes "one continuous course of conduct," the requirement of jury unanimity is satisfied regardless of whether there is agreement among jurors as to "which act" constituted the crime charged. (Emphasis omitted). While the course of conduct in Giwosky was a "short continuous incident that can not be factually separated," the court later clarified in State v. Lomagro that the duration of the course of conduct was not "legally significant." The unanimity requirement is met where multiple acts can be said to constitute "one continuous, unlawful event and chargeable as one count."
The question in Lomagro was whether the aggregation of multiple, conceptually similar acts in a single charged crime was constitutionally permissible as an act of prosecutorial discretion. The language of § 948.025, Stats., plainly shows that the legislature intended to create a single crime, the repeated sexual assault of the same child within a specified time period. The question before us, then, is whether the legislature may, like prosecutors, aggregate conceptually similar acts in a single "course of conduct" crime, albeit for acts committed over an indefinite, and presumably longer, period of time. We conclude that it may.
Molitor, 210 Wis. 2d at 420-421 (citations omitted).
¶ 22. Johnson argues that the Supreme Court's decision in Richardson abrogates Molitor on due process grounds. We disagree. In Richardson, the Supreme Court evaluated a unanimity challenge to the federal "continuing criminal enterprise" statute6 in light of the statute's language and the due process con*379siderations articulated in its decision in Schad. The statute, 21 U.S.C. § 848(a) (1994), defines a "continuing criminal enterprise" (CCE) as a "continuing series of violations" of federal drug laws undertaken by an "organizer" or "supervisor" of the enterprise, in concert with at least five other persons, and from which the defendant derives substantial income. See 21 U.S.C § 848(c) (1994). The district court instructed the jury that it must "unanimously agree that the defendant committed at least three federal narcotics offenses," adding that "[y]ou do not. . .have to agree as to the particular three or more federal narcotics offenses committed by the defendant." The defendant was convicted.
¶ 23. The Supreme Court reversed, holding that to convict under the CCE, the jury must be unanimous not only on the question of whether the defendant committed a "continuous series of violations" of the federal drug laws, but also on the specific "violations" that make up the continuing series. In reaching this conclusion, the Court focused on the language of the statute, historical tradition, and the potential for unfairness. Richardson, 526 U.S. at 818-20. That is, the Court initially engaged in an exercise of statutory interpreta*380tion, and then applied the due process test articulated in Schad.
¶ 24. The Court concluded that the CCE statute's use of the word "violation" to describe the constituent parts of the course of conduct required to comprise the "continuing series" was a legal term of art, and meant that Congress intended each violation to be treated as an element of the offense. Richardson, 526 U.S. at 818-19. Furthermore, the Court concluded that the breadth of the violations that could potentially qualify as part of the series under the statute — ranging from civil penalties for removing drug labels, to simple criminal possession, to endangering human life while manufacturing a controlled substance and possession with intent to deliver large quantities of drugs — raised due process concerns. The Court noted that the federal drug code encompassed "many different kinds of behavior of varying degrees of seriousness," and that this breadth would aggravate the danger of unfairness if the jury were not required to be unanimous about the predicate acts making up the continuing criminal enterprise. Id. at 819. The Court identified two principal concerns: first, by treating predicate violations simply as alternate means of committing the crime, jurors could avoid the specific factual details of each violation and thus cover up potential disagreements about what the defendant did or did not do; second, unless jurors were required to focus on specific factual detail, they might conclude "that where there is smoke there is fire." Id
¶ 25. Applying the Supreme Court's analysis in Richardson to Wis. Stat. § 948.025 does not require us to overrule Molitor or invalidate the statute. To the contrary, as we have set forth above, an examination of the statute's language and an application of the Schad *381due process test for fundamental fairness and rationality yields the same conclusion as that reached in Molitor. Unlike the federal CCE statute at issue in Richardson, Wis. Stat. § 948.025 plainly does not designate the predicate acts of sexual assault as elements of the offense of repeated sexual assault of a child, about which the jury must be unanimous. Rather, the statute explicitly excludes the predicate acts from any unanimity requirement. As such, and in contrast to Richardson, no exercise in statutory interpretation is necessary here.
¶ 26. Furthermore, as we have discussed at length above, the risk of unfairness in dispensing with unanimity on the predicate acts under this statute is not present as it was in Richardson. The range of crimes included as predicate acts under the CCE, totaling approximately 90 numbered sections of the federal criminal code and covering minor civil drug offenses as well as major drug felonies, is far greater than the two types of sexual assault of a child included as predicate acts under Wis. Stat. § 948.025. In Richardson there was insufficient moral equivalence and conceptual similarity in the 90 or so predicate drug crimes included within the ambit of the CCE to sustain an interpretation of the statute that would permit nonunanimity on the predicate acts. Here, the predicate acts of first- and second- degree sexual assault of a child are sufficiently equivalent to justify the legislature's decision to dispense with unanimity on the predicate acts.
¶ 27. Finally, the Supreme Court in Richardson specifically noted that state statutes pertaining to child sexual assault are distinguishable under its analysis:
The closest analogies [the federal government] cites consist of state statutes making criminal such *382crimes as sexual abuse of a minor. State courts interpreting such statutes have sometimes permitted jury disagreement about a "specific" underlying criminal "incident" insisting only upon proof of a "continuous course of conduct" in violation of the law. . . .The state practice may well respond to special difficulties of proving individual underlying criminal acts, which difficulties are absent here. . . .The cases are not federal but state, where this Court has not held that the Constitution imposes a jury unanimity requirement. And their special subject matter indicates that they represent an exception; they do not represent a general tradition or a rule.
Richardson, 526 U.S. at 821-22 (citations omitted). That the Supreme Court excluded this type of state statute from its analysis in Richardson supports our conclusion that Molitor has not been abrogated, and Wis. Stat. § 948.025 is not unconstitutional on unanimous verdict or due process grounds.
¶ 28. Accordingly, we conclude that Johnson has not overcome the presumption of constitutionality that attends the legislative determination to dispense with a unanimity requirement for the individual acts of child sexual assault that comprise the crime of repeated sexual assault of the same child. Under the state and federal constitutional analyses of Molitor, Richardson, and Schad, Wis. Stat. § 948.025 does not violate due process or the right to a unanimous verdict. We affirm the order of the circuit court denying Johnson's motion for a new trial.
By the Court. — The order of the circuit court for Kenosha County is affirmed.
A11 references to the Wisconsin Statutes are to the 1997 — 98 version unless otherwise noted.
The court of appeals stated the question on certification as follows:
Does State v. Molitor, 210 Wis. 2d 415, 421 — 23, 565 N.W.2d 248 (Ct. App. 1997), holding that a jury need only unanimously agree that three or more sexual assaults constitute a "continuing course of conduct” to support a conviction of repeated sexual assault of a child contrary to WIS. STAT. § 948.025 (1997-98), survive Richardson v. United States, 119 S. Ct. 1707 (1999), holding that a jury must also unanimously agree on the specific violations included in the "continuing course of conduct?"
Johnson was also charged with second-degree sexual assault for conduct relating to Andrea V. The jury acquitted him on this count.
Article I, Section 5, Trial by jury; verdict in civil cases, states:
Section 5. The right of trial by jury shall remain inviolate, and shall extend to all cases at law without regard to the amount in controversy; but a jury trial may be waived by the parties in all cases in the manner prescribed by law. Provided, however, that the legislature may, from time to time, by statute provide that a valid verdict, in civil cases, may be based on the votes of a specified number of the jury, not less than five-sixths thereof.
Article I, Section 7, Rights of accused, states:
Section 7. In all criminal prosecutions the accused shall enjoy the right to be heard by himself and counsel; to demand the nature and cause of the accusation against him; to meet the witnesses face to face; to have compulsory process to compel the attendance of witnesses in his behalf; and in prosecutions by indictment, or information, to a speedy public trial by an impartial jury of the county or district wherein the offense shall have been committed; which county or district shall have been previously ascertained by law.
21 U.S.C § 848(c) (1994) says, in pertinent part:
[A] person is engaged in a continuing criminal enterprise if—
*379(1) he violates any provision of [the federal drag laws, i.e.,] this subchapter or subchapter II of this chapter the punishment for which is a felony, and
(2) such violation is a part of a continuing series of violations of [the federal drug laws, i.e.,] this subchapter or subchapter II of this chapter—
(A) which are undertaken by such person in concert with five or more other persons with respect to whom such person occupies a position of organizer [or supervisor or manager] and
(B) from which such person obtains substantial income or resources.