¶ 35. (concurring in part, dissenting in part). The majority concludes that *79whether a "court of competent jurisdiction" issued a child support order is not an element of the crime of failure to pay child support under Wis. Stat. § 948.22. Majority op., ¶ 2. With this conclusion, I agree. The crime of felony child support contains the following elements: (1) that the defendant intentionally failed to provide child support; (2) that the intentional failure to provide support continued for 120 or more consecutive days; and (3) that the defendant knew or reasonably should have known that he was legally obligated to provide child support. See Wis JI — Criminal 2152 (2001); Wis. Stat. § 948.22(l)(a) (2001-02).1
¶ 36. The majority then concludes that because proof that a court of competent jurisdiction issued a child support order is not an element of the offense of failure to pay child support, the circuit court was not required to give the jury instruction requested by Smith in order to satisfy the constitutional requirement that each element of the crime for which a defendant is charged be tendered to the jury. Majority op., ¶ 16. The second conclusion does not follow the first. Even though there is no separate element for a court of competent jurisdiction, Smith has nonetheless been deprived of jury consideration of the first and third elements of the offense as they relate to the validity of a child support order itself. Accordingly, while I agree that the decision of the court of appeals must be reversed with respect to its handling of the sufficiency of the evidence claim,2 I respectfully dissent from that portion of the majority opinion that affirms the trial court.
*80¶ 37. Prior to trial for two counts of failure to pay child support, Timothy Smith challenged the validity of the Maine child support order he was accused of violating on multiple grounds. First, because his divorce took place in the district court of Waldo County, Maine, Smith argued that the Sagadahoc County Superior Court in Maine that issued the child support order was 'not a "court of competent jurisdiction" as that term is used in Wisconsin's failure to pay child support crime.3 See Wis. Stat. § 948.22(l)(a). Second, he argued that the Maine Department of Human Services had no authority to prosecute the Uniform Reciprocal Enforcement of *81Support Act (URESA) petition, rendering the child support order invalid. Third, Smith argued that the Maine child support court order was unlawful because it did not state on which provision of law it was based.
¶ 38. Smith specifically argued that his challenges to the Maine child support order went to the third element necessary to prove the charges against him, namely, that he knew or reasonably should have known that he was legally obligated to pay child support. He argued that if he did not believe the order to be valid, then he lacked the intent necessary to constitute the third element. Thus, Smith argued, the question on the validity of the child support order was a fact question for the jury because it ultimately determines whether he had the requisite criminal state of mind.4
¶ 39. The trial court concluded that whether the Maine child support order was valid was a question for the court, not the jury. The court gave "full faith and credit" to the Maine order, and refused to permit Smith to collaterally attack the order. The trial court further refused to instruct the jury on the issue or to allow the defendant to present direct evidence on the issue. State v. Smith, 2004 WI App 116, ¶ 3, 275 Wis. 2d 204, 685 N.W.2d 821. The trial court also refused to instruct the jury that it was required to find, as a separate element of the offense, that a court of competent jurisdiction issued the child support order. The court only allowed Smith to present evidence as to the general concepts involved with jurisdiction, in addition to why he believed he was not legally obligated to comply with the child support order. Id.
*82¶ 40. The court of appeals reversed the trial court, concluding that there are four elements to this offense, including that a court of competent jurisdiction issued the child support order. Id., ¶ 9. This court's majority correctly determines that there are only three elements, those stated in Wis JI — Criminal 2152. Majority op., ¶ 15. With that conclusion in hand, however, both decisions miss the import of Smith's argument.
¶ 41. As noted above, the crime of felony child support contains the following elements: (1) that the defendant intentionally failed to provide child support; (2) that the intentional failure to provide support continued for 120 or more consecutive days; and (3) that the defendant knew or reasonably should have known that he was legally obligated to provide child support. See Wis JI — Criminal 2152. As is evident, for Smith to have committed this offense, he had to intentionally fail to provide child support, which he knew or reasonably should have known that he was legally obligated to provide.5 The State had to prove that Smith had actual or constructive notice of a legal obligation to provide child support. Whether such an obligation actually existed, therefore, cuts to the heart of Smith's legal defense.
¶ 42. To begin with, "child support" is defined in pertinent part as "an amount which a person is ordered to provide for support of a child by a court of competent jurisdiction in this state or in another state . . . ." Wis. Stat. § 948.22(l)(a). In order to intentionally fail to provide child support, a court of competent jurisdiction had to issue such an order. Otherwise, by definition, no offense could have been committed. Child support is part of the first element of this offense. One cannot *83intentionally fail to pay that which does not exist. Absent a valid order, Smith simply has no legal obligation whatsoever.
¶ 43. The July Instructions Committee certainly recognized the fact that the question of whether a valid support order existed might come into play. In defining the first element concerning the intentional failure to provide support, the Committee noted as follows: "For purposes of instructing the jury, the Committee concluded that definition of 'support' would rarely be necessary in the usual case. Should the facts present an issue, the statutes referenced in subs. (l)(a) and (c) may offer some guidance . . . ." See Wis JI — Criminal 2152 cmt. n.4. Smith attempted to raise facts that would present the issue, but was thwarted by the trial court. Smith set forth his theory that the Maine order was not valid, but was not allowed to present any evidence to the jury. He requested the court to define "child support," consistent with the Committee's note that the statute may offer some guidance, but the trial court declined to do so. In short, he was precluded from presenting a defense against one of the essential elements that the State had to prove: whether he intentionally failed to provide child support.
¶ 44. The trial court did allow Smith to present evidence as to why he believed he was not legally obligated to comply with the child support order. Without being able to challenge the order itself, and without child support being defined for the jury, his defense to the third element was likewise completely undercut. There was simply no way for the jury to understand the basis of his challenge regarding his knowledge, actual or constructive, of an obligation that he posited did not exist. The jury was not informed that the order had to be issued by a court of competent jurisdiction.
*84¶ 45. Jurisdictional challenges to the validity of foreign judgments are a legitimate matter of inquiry whenever the enforcement of the foreign judgment is sought. Hansen v. McAndrews, 49 Wis. 2d 625, 630, 183 N.W.2d 1 (1971). While the general rule precludes collateral attacks of a valid judgment,6 when a court acts in excess of its jurisdiction its orders and judgments are void and may be challenged at any time. Kohler Co. v. DILHR, 81 Wis. 2d 11, 25, 259 N.W2d 695 (1977). The fact that a party is dilatory or lackadaisical in his or her efforts to overturn the judgment is irrelevant. Id. " 'It is the duty of the court to annul an invalid judgment.'" Id. (quoting Halbach v. Halbach, 259 Wis. 329, 331, 48 N.W2d 617 (1951)).
¶ 46. Void judgments cannot be validated by consent, ratification, waiver, or estoppel. Kohler, 81 Wis. 2d at 25. Void judgments may also be attacked collaterally, id., including foreign judgments. See West v. West, 82 Wis. 2d 158, 262 N.W.2d 87 (1978)7
*85¶ 47. Smith has directly challenged the authority of the Sagadahoc Superior Court to issue the child support order. Accordingly, he was not precluded from collaterally attacking the validity of that order if that court acted in excess of its jurisdiction. By not allowing Smith to present evidence in support of his challenge, and by refusing to instruct the jury as to the definition of "child support," the trial court effectively impaired Smith's right to defend against the first element of the offense.
¶ 48. Due process protects a person from conviction except "upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged." In re Winship, 397 U.S. 358, 365 (1970); see also State v. Smith, 117 Wis. 2d 399, 415, 344 N.W.2d 711 (Ct. App. 1983). The State had the burden of proving that Smith intentionally failed to provide child support in this matter, as well as his actual or constructive knowledge of his legal obligation to provide that support. The trial court failed to correctly instruct the jury with respect to the first element by refusing to define "child support."8 Omissions in jury instructions are subject to a harmless error analysis. See State v. *86Harvey, 2002 WI 93, ¶ 6, 254 Wis. 2d 442, 647 N.W2d 189. I conclude that the error cannot be harmless where, as here, not only was the jury not instructed with respect to the definition of child support, but also the defense was precluded from presenting evidence with respect to the first and third elements.
¶ 49. The majority briefly discusses how the concept of a "court of competent jurisdiction" encompasses the concepts of personal jurisdiction, subject matter jurisdiction, and a court's competency. Majority op., ¶¶ 18-20. As the majority correctly notes, subject matter jurisdiction is the power of the courts to hear and determine cases of the general class to which the proceedings belong. United States v. Morton, 467 U.S. 822, 828 (1984); Kohler Co. v. Wixen, 204 Wis. 2d 327, 336, 555 N.W.2d 640 (Ct. App. 1996). Personal jurisdiction refers to a court's power to enter a judgment against an individual party. Kohler, 204 Wis. 2d at 336. A court's competency is not jurisdictional, but is defined as "the power of a court to exercise its subject matter jurisdiction" in a particular case. Id. at 337.
¶ 50. In Wisconsin, Article VII, Section 8 of the Wisconsin Constitution provides that: "[e]xcept as otherwise provided by law, the circuit court shall have original jurisdiction in all matters civil and criminal within this state." See also Village of Trempealeau v. Mikrut, 2004 WI 79, ¶ 8, 273 Wis. 2d 76, 681 N.W.2d 190. Thus, "[n]o circuit court is without subject matter *87jurisdiction to entertain actions of any nature whatsoever." Mueller v. Brunn, 105 Wis. 2d 171, 176, 313 N.W.2d 790 (1982). But see State v. Bush, 2005 WI103, _ Wis. 2d _, 699 N.W.2d 80 (released this same date). This constitutional rule regarding Wisconsin jurisdiction has not always been in effect, however, as our constitution was amended in 1977 to create a unified court system with original jurisdiction vested wholly in the circuit court. See Eberhardy v. Cir. Ct. for Wood Co., 102 Wis. 2d 539, 550-51, 307 N.W.2d 881 (1981). Prior to that time, jurisdiction existed within the Supreme Court, circuit courts, probate courts, county courts, municipal courts, and with justices of the peace. See Wis. Const, art. VII, § 8 (1975) and Wis. Stat. ch. 252 (1975) (circuit courts);9 Wis. Stat. ch. 253 (1975) (county courts); Wis. Const. art. VII, § 2 (municipal courts);10 Wis. Const. art. VII, § 16 (1975) (tribunals of *88conciliation);11 Wis. Const, art. VII, § 15 (1965) (justices of the peace);12 Wis. Const, art. VII, § 14 (judges of probate).13 Our current jurisprudence regarding subject matter jurisdiction and a court's competence to act *89in furtherance of that jurisdiction may not have been applicable prior to the creation of the unified court system.
¶ 51. Similarly, Wisconsin's unified court system is not necessarily the rule in other jurisdictions. Issues of subject matter jurisdiction and a court's competency to exercise that jurisdiction may carry very different meanings in other states. Smith has every right to put the State to its burden of proof. That includes challenging the order for child support in the first instance.
¶ 52. I agree with the majority that the court of appeals' decision must be reversed as to the sufficiency of evidence claim, but would nevertheless affirm the court of appeals determination that reversal of the trial court is warranted, and remand this matter to the circuit court for a new trial.
¶ 53. For the foregoing reasons, I respectfully concur in part, and dissent in part, and would remand this matter to the circuit court for a new trial.
All references to the Wisconsin Statutes are to the 2001-02 version.
The court of appeals' decision with respect to sufficiency of the evidence was premised on its erroneous conclusion that the *80State had to prove as one of the elements that a court of competent jurisdiction issued an order requiring the defendant to provide child support. State v. Smith, 2004 WI App 116, ¶ 9, 275 Wis. 2d 204, 685 N.W2d 821. Because the State failed to present the jury with any evidence as to the laws of Maine, or give to the jury sufficient facts from which it could have resolved the questions of subject matter and personal jurisdiction concerning whether the court which issued the order was one of competent jurisdiction, the court of appeals reasoned that the evidence was insufficient. Id., ¶ 33. Because that court mischaracterized the elements that had to be proved, it similarly mischaracterized the evidence needed by the State to prove its case. I would reverse the court of appeals' decision with respect to sufficiency of the evidence.
Without assessing the validity of Smith's argument, I note that Maine's judicial system is comprised of a supreme court and two different trial courts, superior courts, and district courts. Me. Rev. Stat. Ann. tit. 4, §§ 1-57 (West 2004) (supreme court); Me. Rev. Stat. Ann. tit. 4, §§ 101-121 (West 2004) (superior courts); Me. Rev. Stat. Ann. tit. 4, §§ 151-184 (West 2004) (district courts). Within the district court is a family division. Me. Rev. Stat. Ann. tit. 4, § 183 (West 2004). According to the family division's rules, the family division has jurisdiction over child support. Rules for the Family Division of the Maine District Court, I.A.
Smith currently argues that if the Maine Superior Court lacked the authority to issue the child support order for any reason, a criminal charge cannot stand.
The second element is not at issue in this case.
Kehl v. Britzman, 258 Wis. 513, 516, 46 N.W2d 841 (1951). Accordingly, I agree with the majority that Smith is precluded from challenging either the authority of the Maine Department of Human Services to prosecute the URESA petition or the fact that the Maine child support order was unlawful because it did not state on which provision of law it was based. Majority op., ¶¶ 21 — 22.1 respectfully disagree with the majority's collateral attack analysis with respect to jurisdictional challenges, however.
This court has previously indicated that if a jurisdictional issue has been fully litigated in a foreign court and is not subject to collateral attack in that state, then the forum court is bound by the judgment as to jurisdiction. Hansen v. McAndrews, 49 Wis. 2d 625, 630, 183 N.W.2d 1 (1971). Nevertheless, this court noted exceptions to this rule that included relief from a void judgment which appears or purports to be valid, particularly when due process is violated. Id. at 630 n.5, 631 and 637. Thus, *85even though Smith failed to follow through with his appeal in Maine, he is not precluded from raising his challenge to the Maine court's jurisdiction here.
It is not unusual to find definitions of essential elements or essential facts in the standard jury instructions. Indeed, the standard instructions are full of such examples. For example, "truant" as part of the third element of the offense is defined in Wis JI — Criminal 2173, Contributing to Truancy. The definitions of "drive" and "operated" are included with respect to the first element throughout the drunk driving and prohibited alcohol concentration instructions. See Wis JI — Criminal 2660, etc. "Sexual intercourse" and "sexual contact" are defined throughout the sexual assault instructions with respect to that *86element. See Wis JI — Criminal 1200, etc. These examples are not meant to be exhaustive. They are illustrative of the fact that this court and the Jury Instructions Committee have long recognized the importance of defining legal terms to the jury so that it can better understand the elements of the crime charged in fulfilling its decision-making function. The jury should have been so instructed in this case.
Wisconsin Const, art. VII, § 8 (1975), stated:
The circuit courts shall have original jurisdiction in all matters civil and criminal within this state, not excepted in this constitution, and not hereafter prohibited by law; and appellate jurisdiction from all inferior courts and tribunals, and a supervisory control over the same. They shall also have the power to issue writs of habeas corpus, mandamus, injunction, quo warranto, certiorari, and all other writs necessary to carry into effect then-orders, judgments and decrees, and give them a general control over inferior courts and jurisdictions.
Wisconsin Const, art. VII, § 2 (1975), stated in part:
The judicial power of this state, both as to matters of law and equity, shall be vested in a supreme court, circuit courts, and courts of probate. The legislature may also vest such jurisdiction as shall be deemed necessary in municipal courts, and may authorize the establishment of inferior courts in the several counties, cities, villages or towns, with limited civil and criminal jurisdiction. Provided, that the jurisdiction which may be vested in municipal courts shall not exceed in their respective municipalities *88that of circuit courts in their respective circuits as prescribed in this constitution; and that the legislature shall provide as well for the election of judges of the municipal courts as of the judges of inferior courts, by the qualified electors of the respective jurisdictions. The term of office of the judges of the said municipal and inferior courts shall not be longer than that of the judges of the circuit courts.
Wisconsin Const, art. VII, § 16 (1975), provided;
The legislature shall pass laws for the regulation of tribunals of conciliation, defining their powers and duties. Such tribunals may be established in and for any township, and shall have power to render judgment to be obligatory on the parties when they shall voluntarily submit their matter in difference to arbitration, and agree to abide the judgment or assent thereto in writing.
Wisconsin Const, art. VII, § 15 (1965), read:
The electors of the several towns at their annual town meeting, and the electors of cities and villages at their charter elections except in cities of the first class, shall, in such manner as the legislature may direct, elect justices of the peace, whose term of office shall be for 2 years and until their successors in office shall be elected and qualified. In case of an election to fill a vacancy occurring before the expiration of a full term, the justice elected shall hold for the residue of the unexpired term. Their number and classification shall be regulated by law. And the tenure of 2 years shall in no wise interfere with the classification in the first instance. The justices thus elected shall have such civil and criminal jurisdiction as shall be prescribed by law.
Wisconsin Const, art. VII, § 14 (1975), stated:
There shall be chosen in each county, by the qualified electors thereof, a judge of probate, who shall hold his office for two years and until his successor shall be elected and qualified, and whose jurisdiction, powers and duties shall be prescribed by law. Provided, however, that the legislature shall have power to abolish the *89office of judge of probate in any county, and to confer probate powers upon such inferior courts as may be established in said county.
See also Wisconsin Const, art. VII, § 2 (1975).