dissenting:
I respectfully dissent. Section 19-4-105(1)(a) (establishing a presumption of pa*516ternity) and section 19-4-107(1)(b) (limiting the period within which a nonpaternity action must be brought), 8B C.R.S. (1988 Supp.), should be read together so as to preclude a presumed father from raising the defense of nonpaternity in an action for child support after the five year statute of limitations has run. Accordingly, I would reverse.
The majority concludes that the five year statute of limitations on nonpaternity claims does not bar a presumed father from asserting nonpaternity as a defense in a child support action instituted against him more than five years after the child’s birth. Under its analysis, the statute of limitations applies only to an action for nonpaternity brought by the presumed father. I do not find that construction consistent with the Uniform Parentage Act (U.P.A.), sections 19-4-101 to 19-4-129, 8B C.R.S. (1988 Supp.), and I believe the majority’s interpretation will vitiate the five year statute of limitations for nonpaternity actions.
Section 4 of the U.P.A. creates certain presumptions regarding who bears the parental obligations as a child’s father. Section 19-4-105, 8B C.R.S. (1988 Supp.). Section 6 of the U.P.A., section 19-4-107, 8B C.R.S. (1988 Supp.), establishes who may bring an action to assert either paternity or nonpaternity and, in certain instances, limits the time within which an action may be brought. Section 19-4-107(1) permits a child, his natural mother, a man presumed to be his father under section 19-4-105(l)(a), (1)(b) or (1)(c),1 the State, the Department of Social Services or a county department of social services to bring an action to establish paternity or nonpaternity under various circumstances. Subsection (a) permits an action to be brought at any time to establish paternity whereas subsection (b) requires that an action to establish nonpaternity be brought within five years of the child’s birth.2 The different time limits on actions to establish paternity and actions to establish nonpaternity reflect a legislative judgment that there is a fundamental difference between the two types of actions. The basic purpose of the U.P.A. is to promote and protect the legitimacy of children. By allowing a much shorter period to bring a nonpaternity action, the act clearly has struck a balance in favor of the child, elevating his interests over that of the presumed father.
Another U.P.A. state, Minnesota, emphasized this point in construing its three year nonpaternity statute of limitations as follows:
The obvious intent of the three-year statute of limitations is to make the pre*517sumption of legitimacy conclusive once a child reaches three years of age. The three-year statute of limitations is absolute in that it bars action even if the presumed father obtains knowledge of illegitimacy after the running of the statute.
Pierce v. Pierce, 374 N.W.2d 450, 452 (Minn.Ct.App.1985) (emphasis in original). In a subsequent case, the same court in Clay v. Clay, 397 N.W.2d 571, 577 n. 3 (Minn.Ct.App.1986), appeal dismissed, Clay v. Clay, 484 U.S. 804, 108 S.Ct. 49, 98 L.Ed.2d 14 (1987), explained why the U.P.A. treats declarations of paternity differently from nonpaternity actions:
Public policy is served when a party has 19 years to seek adjudication of parentage, which adjudication establishes a parent/child relationship with all its attendant legal and social benefits for the child. Conversely, that same public policy is served when a party must within three years after a child’s birth bring an action to declare non-parentage, when parentage has been presumed by law because of marriage or attempted marriage, and such declaration of non-parentage would deprive a child of legal and social benefits previously enjoyed.
The Clay case involved facts similar to the case now before us. Clay was the presumed father of the child T.C. because T.C. was born in 1981 while Clay was married to T.C.’s mother. The parents were divorced in 1982 and T.C.’s paternity was not contested in that proceeding. In 1985, Clay brought a nonpaternity action and the county brought a separate action against Clay seeking child support for T.C. The Minnesota Court of Appeals held that Clay was barred from asserting that he was not T.C.’s father because the three year statute of limitations had run. The court concluded that “[permitting a challenge to the legitimacy of a child more than three years after its birth would defeat the statutory purpose of promoting legitimacy.” Id. at 577 (footnote omitted). The court went on to uphold the constitutionality of its application of the statute of limitations.
These Minnesota cases are particularly important in analyzing the issue presented by this case because of section 19-4-126, 8B C.R.S. (1986 Repl.Vol.) which requires this court to construe the U.P.A. “to effectuate its general purpose to make uniform the law with respect to the subject of this article among states enacting it.” As the Clay case indicates, the presumptions of paternity created by the U.P.A. are not mere evidentiary presumptions. If a paternity presumption is not contested within the five year period of the statute of limitations, then the presumed father must bear the obligations of paternity as a matter of substantive law.
The substantive nature of paternity presumptions was addressed in a recent United States Supreme Court decision, Michael H. v. Gerald D., — U.S.-, 109 S.Ct. 2333, 105 L.Ed.2d 91 (1989). In Michael H., the petitioner sought to have himself declared to be the father of a child, Victoria. It was undisputed that Michael H. was Victoria’s natural father and that Victoria’s mother was married to another man at all relevant times. California has adopted the U.P.A. in modified form.3 Unlike Colorado, California, through § 621 of its evidence code, has made certain of the U.P.A. § 4 presumptions (e.g., the California equivalent of our section 19-4-105(1)) irrebuttable. Section 621 states, in relevant part, as follows:
(a) Except as provided in subdivision (b), the issue of a wife cohabiting with her husband, who is not impotent or sterile, is conclusively presumed to be a child of the marriage.
(b) Notwithstanding the provisions of subdivision (a), if the court finds that the conclusions of all the experts, as disclosed by the evidence based upon blood tests performed pursuant to Chapter 2 (commencing with Section 890) of Division 7 are that the husband is not the father of the child, the question of paternity of the husband shall be resolved accordingly.
When the conclusive presumption established by § 621 does not apply, such as *518when the child is born to a wife not cohabi-tating with her husband, then the normal rebuttable presumption of U.P.A. § 4 applies. Vincent B. v. Joan R., 126 Cal. App.3d 619, 625, 179 Cal.Rptr. 9, 11-12 (1981).
Petitioner Michael H. asserted before the Supreme Court that, because § 621 made the presumed father’s paternity “conclusive” and thereby precluded him as Victoria’s natural father from challenging the parental status of the husband of Victoria’s mother, his substantive and procedural due process rights were violated. The court rejected these arguments. Michael H., 109 S.Ct. at 2342. The plurality refused to characterize the “presumed father” status created by California law as a mere procedural device:
We believe this claim derives from a fundamental misconception of the nature of the California statute. While § 621 is phrased in terms of a presumption, that rule of evidence is the implementation of a substantive rule of law. California declares it to be, except in limited circumstances, irrelevant for paternity purposes whether a child conceived during and born into an existing marriage was begotten by someone other than the husband and had a prior relationship with him.
(Emphasis in original.) Michael H., 109 S.Ct. at 2340. The plurality found that the “conclusive presumption” in reality reflected a substantive policy choice of the state “that given a certain relationship between husband and wife, the husband is to be held responsible for the child, and that the integrity of the family unit should not be impugned.” Michael H., 109 S.Ct. at 2340 (quoting Vincent B. v. Joan R., 126 Cal.App.3d 619, 623, 179 Cal.Rptr. 9, 10 (1981)). See also Michelle W. v. Ronald W., 39 Cal.3d 354, 362-63, 216 Cal.Rptr. 748, 752, 703 P.2d 88, 92 (1985) (“Thus, section 621 does not purport to factually determine the biological paternity of a child.... Here, [plaintiff’s] private interest in establishing a biological relationship in a court of law is overridden by the substantial state interests in familial stability and the welfare of the child.”).
In my view, the Colorado U.P.A. presumptions should also be recognized as substantive rules of law adopted by the legislature, not as mere evidentiary presumptions. The section 19-4-107 five-year limitation to bring an action to assert non-paternity reflects a legislature decision that, if the presumed father fails to bring such an action, the presumed father is precluded from challenging his legal obligations of parenthood.4 It is legally irrelevant after that time whether or not the presumed father is in fact the biological father.
My interpretation of the substantive purpose of section 19-4-107(1) is supported by the comment to § 6 of the U.P.A. (section 19-4-107(1)) which states in relevant part:
This section consists of two major parts. Subsections (a) and (b) deal with the action to declare or dispute the existence of the father and child relationship presumed under Section 4(a) [19-4-105(1)]. Attack on the presumptions based on marriage or on a relationship between the parents that resembles marriage is restricted to a limited circle of potential contestants and in point of time. Presumptions created in other circumstances may be attacked more freely.
(Emphasis added.) Section 19-4-105(1) together with the time limit of section 19-4-107(1) does not establish a set of scientific principles by which the biological connection of father and child most accurately may be proven. A court cannot alter biological facts but, following the statute, it can and does impose legal obligations apart from those facts and in certain instances in *519the face of them. See Lehr v. Robertson, 463 U.S. 248, 261, 103 S.Ct. 2985, 2993, 77 L.Ed.2d 614 (1983).
Construing the five year statute of limitations as not applicable to a defense based on nonpaternity defeats the purposes of the U.P.A. In seeking to avoid what the majority sees as one injustice — the asserted potential for plaintiff mothers or governmental agencies to wait five years before asserting claims against presumed fathers who then are precluded from offering a defense — the majority would open the door to a far greater injustice to the child by subjecting his legitimacy to such a belated challenge. See generally, Notes, Human Leukocyte Antigen Testing: Technology Versus Policy in Cases of Disputed Parentage, 36 Vand.L.Rev. 1587, 1607 (1983) (urging a 3-year statute of limitations to disprove paternity in order to protect the economic and emotional interests of the child).
- I note initially that the majority’s concern that a mother or other representative of the child purposely would wait five years before bringing an action to enforce paternity obligations on an unsuspecting presumed father is speculative at best. In any case, the existing doctrine of equitable estoppel would protect against such abuses. See Strader v. Beneficial Finance Co. of Aurora, 191 Colo. 206, 551 P.2d 720, at 724 (1976) (where a party by its acts or omissions contributes to the running of a statute of limitations, the doctrine of equitable estoppel will prevent its raising that defense). This respondent has presented no facts which would indicate that the doctrine is applicable. To the contrary, the facts indicate that he was told of the child’s birth shortly after it occurred, that he knew he was listed as the baby’s father on the birth certificate and that he knew he was not the natural father. Had he wished to contest the child’s paternity, he should have done so within the five year statute of limitations. Again, these facts are similar to those in Clay where the presumed father knew he was not T.C.’s father but failed to bring a timely action for nonpater-nity because he “couldn’t afford it” and then decided to raise the issue to avoid paying child support. 397 N.W.2d at 573.
Like the Minnesota Court of Appeals, we too should reject this attempt to circumvent the statute of limitations. Under the holding of the majority, the passing of the statute of limitations becomes irrelevant. Years after the child is born, the presumed father will be free to ignore parental obligations previously unquestioned and to await the bringing of a lawsuit by the mother where he can challenge the child’s paternity. There would be little or no incentive for a presumed father to bear the expense of bringing a nonpaternity action if, as the majority holds, he can assert nonpaternity as a defense at any time. With this loophole, the statute of limitations on nonpaternity actions will have no real effect.
While I recognize the common law rule allowing a defendant to assert as a defense what the statute of limitations would preclude him from raising as an affirmative claim, its application is inappropriate here when it would so clearly defeat the legislative purpose of this statute. Following the reasoning of Michael H. and Clay, I would hold that the presumption of paternity becomes a rule of law after five years have passed. The presumed father is the legal father after that time and must bear the legal obligations that follow from such status.
With respect to the respondent’s assertion that denying him the right to raise nonpaternity as a defense in this action would violate the Equal Protection and Due Process Clauses of the state and federal constitutions, those arguments need not be considered because they were not raised at either the district court or at the court of appeals. This court will not consider constitutional issues raised for the first time on appeal. Colgan v. Dept. of Revenue, 623 P.2d 871 (Colo.1981). In any event, the challenges seem doubtful in light of the United States Supreme Court’s decision upholding California’s denial of any right in the natural father to challenge the presumed parental status of the husband of the child’s mother. Michael H., 109 S.Ct. *520at 2340. See also Clay, 397 N.W.2d at 576-77 (upholding, on due process grounds, constitutionality of U.P.A. nonpaternity statute of limitations as applied).
For these reasons, I dissent.
. Section 19-4-105 provides, in relevant part: Presumption of paternity. (1) A man is presumed to be the natural father of a child if:
(a) He and the child’s natural mother are or have been married to each other and the child is born during the marriage, within three hundred days after the marriage is terminated by death, annulment, declaration of invalidity of marriage, dissolution of marriage, or divorce, or after a decree of legal separation is entered by a court;
(b) Before the child’s birth, he and the child’s natural mother have attempted to marry each other by a marriage solemnized in apparent compliance with law, although the attempted marriage is or could be declared invalid; and
(I)If the attempted marriage could be declared invalid only by a court, the child is born during the attempted marriage or within three hundred days after its termination by death, annulment, declaration of invalidity of marriage, dissolution of marriage, or divorce; or
(II)If the attempted marriage is invalid without a court order, the child is born within three hundred days after the termination of cohabitation;
(c)After the child’s birth, he and the child’s natural mother have married, or attempted to marry, each other by a marriage solemnized in apparent compliance with law, although the attempted marriage is or could be declared invalid; and
(I) He has acknowledged his paternity of the child in writing filed with the court or registrar of vital statistics;
(II) With his consent, he is named as the child's father on the child’s birth certificate; or
(III) He is obligated to support the child under a written voluntary promise or by court order; ....
. As the majority correctly observes, however, actions to establish paternity are limited elsewhere in the statute. See maj. op. at 511 (paternity action on behalf of child must be brought within 18 years; paternity action by child must be brought within 21 years).
. See Cal.Civ.Code Ann. § 7000, et seq. (West 1983).
. I note that under section 19-4-105(2), 8B C.R.S. (1988 Supp.), if a court decree establishes the paternity of the child in a man other than the presumed father, then the presumption of paternity is rebutted. My interpretation of the effect of section 19-4-107, which makes such paternity normally unassailable by the presumed father, need not alter this result. It is consistent with legislative policy that a presumed father who has failed to challenge paternity within five years of the birth of the child ought to bear parental obligations unless there is a court determination finding paternity in another man.