Opinion by JUDGE HUME

This appeal arises from a custody proceeding that followed a voluntary private placement of a child, C.C.R.S., by his biological mother, C.R.S., in anticipation of formal relinquishment and adoption proceedings as permitted by § 19-5-104(1)(d), C.R.S. (1993 Cum. Supp.). The mother appeals from a district court order, entered pursuant to § 14-10-123, C.R.S. (1987 Repl. Vol. 6B), which awarded petitioners, T.A.M. and M.A.M., legal and physical custody of the child, subject to the mother's continuing right of visitation. We affirm.

The record on appeal is comprised of certain pleadings, motions, documents, and the final court order awarding custody to the petitioners, as designated by stipulation of the parties on appeal. No transcripts of any hearings conducted before the court or the court magistrate have been included in the record before us. The facts stated herein have been extracted from the documents in the limited record and from the briefs on appeal, and they are essentially undisputed.

During her pregnancy, the mother, then 23 years old and unmarried, made the decision to relinquish her child at birth for adoption. The mother and petitioners were brought together through relatives and mutual acquaintances, and an agreement for private placement was struck prior to the child's birth. The agreement was memorialized in two separate documents which the mother executed on March 6, 1990, the day after the birth of C.C.R.S. Those two documents were appended to the Petition for Custody filed by petitioners in September 1990, and they are included in the record on appeal.

One of the two documents, styled as a Custody Agreement, contains recitals that C.R.S. is the mother of the child born March 5, 1990, and that the identity of the child's father is unknown. It further recites that the mother also signed a Petition for Relinquishment of her own parental rights and for termination of the parental rights of the unknown father for filing by petitioners in relinquishment and adoption proceedings after the expiration of one year.

The Custody Agreement purports to grant full custody of the child to the petitioners, including authority to authorize medical treatment and make educational and religious decisions concerning the child, pending finalization of adoption proceedings. In addition, the Custody Agreement pledges the mother's cooperation in obtaining counseling necessary for relinquishment proceedings and an acknowledgment of her awareness of her right to independent legal counsel. It also states that the attorney who had prepared the Custody Agreement and the Petition for Relinquishment did not represent the mother.

The Petition for Relinquishment, which also was signed by the mother on March 6, 1990, contains an averment that she is one-half caucasian and one-half American Indian, without tribal membership or affiliation, and that while the identity of the child's father is unknown to her, the father could be one of a number of different men, none of whom are of American Indian heritage; that the mother's desire to relinquish is based upon her perception that she will be unable to provide a suitable social environment or necessary financial support for the child's needs; and that her desire to relinquish is voluntary and motivated by her consideration of the best interests of the child.

In addition, the Petition for Relinquishment recites, in some detail, the mother's understanding of the legal effects of relinquishment and adoption processes pursuant to Colorado law. It also avers that the mother expressly consents to custodial placement of the child with petitioners both before and after entry of an order of relinquishment and to their ultimate adoption of the child.

Pursuant to the agreement of the parties, petitioners took physical custody of C.C.R.S. immediately after his birth, and he has continued to reside in their household up to the present time. On August 31, 1990, nearly six months after the child had been placed with the petitioners, an agent for the mother advised petitioners' counsel that she wanted the child returned to her. However, the mother did not then make any personal or written demand for return of the child, nor did she initiate any proceedings seeking to establish or restore her right to custody of C.C.R.S.

On September 13, 1990, petitioners initiated a custody proceeding under the provisions of § 14-10-123, alleging that, during the period of six or more months that the child had lived with them, a strong bond had developed between themselves and the child and that the child's best interests would be served by an award of legal custody to them. They contemporaneously filed a motion for a temporary order seeking to restrain the mother from interfering with petitioners' physical care and custody of the child, which was granted ex parte by the court magistrate. After a hearing held on October 30, 1990, which the mother did not attend, the magistrate granted petitioners' motion for temporary custody of C.C.R.S.

Thereafter, the Oglala Sioux Indian Tribe sought to intervene and effectuate a transfer of jurisdiction over the proceedings pursuant to the Indian Child Welfare Act. Counsel was appointed to represent the mother, and a guardian ad litem was appointed to represent the best interests of the child.

After a series of continuances requested by the Tribe, an order transferring jurisdiction was entered by the magistrate and subsequently reversed by order of the district court on July 23, 1991, and that ruling is not challenged here. Thereafter, additional delays were caused by the withdrawal of the mother's counsel, appointment of new counsel, and the latter's preparation for trial of the custody proceeding.

During this period, on June 17, 1991, the mother filed a renunciation of both the Custody Agreement and the Petition for Relinquishment which she had previously executed and requested that she be awarded custody of C.C.R.S. That filing was accompanied by her affidavit containing averments that she did not fully understand the two documents she had executed after the child's birth and that she had "changed her mind" about relinquishing her rights and consenting to the child's being adopted.

In addition, sometime prior to the hearing, the mother apparently advised her counsel that a man had acknowledged to her that C.C.R.S. was his child and had stated a willingness to help her in supporting him. That man's identity was revealed to the court and to petitioners' counsel, and the man was served with notice of the custody proceeding in early March 1992. No appearance has been made in such proceeding by or on behalf of that putative father. Nor does the record contain evidence in the form of blood tests relative to such alleged paternity.

After conducting a two-day bench trial in May 1992, the district court entered the permanent custody order now in question on May 26, 1992. The court made comprehensive and detailed findings as to why the best interests of the child would be served by his remaining in the legal and physical custody of the petitioners. Those findings are not disputed here, and they must be presumed to be supported by evidence in the record, since no trial transcript has been certified as a part of the record on appeal. See Schleiger v. Schleiger, 137 Colo. 279, 324 P.2d 370 (1958).

I.

The mother first argues that petitioners lacked standing to seek custody under § 14-10-123 of the Uniform Dissolution of Marriage Act (Dissolution Act). We disagree.

Our primary function in interpreting a statute is to ascertain and give effect to the intent of the General Assembly, choosing a construction to further the purpose of the legislative scheme. And, while uniform statutes generally should be construed to bring uniformity to the law in the various states adopting them, other factors must also be considered. In re Marriage of Cargill, 843 P.2d 1335 (Colo. 1993). Dissimilarities in the statutes as adopted by the various states must also be considered, and the general rules of statutory interpretation must be applied in an effort to determine and effectuate the intent of the General Assembly. In re Marriage of Wells, 850 P.2d 694 (Colo. 1993).

The standing of non-parents to litigate claims and to be awarded custody of children against parental interests was well established in Colorado prior to the adoption of the Dissolution Act in 1971. See Rippere v. Rippere, 157 Colo. 29, 400 P.2d 920 (1965); Root v. Allen, 151 Colo. 311, 377 P.2d 117 (1962); Walcott v. Walcott, 139 Colo. 37, 336 P.2d 298 (1959).

In 1971, the Colorado General Assembly adopted a provision governing custody proceedings from the Uniform Marriage and Divorce Act (Uniform Act). Compare Colo. Sess. Laws 1971, ch. 130, § 46-1-23 at 529 with the Uniform Marriage and Divorce Act § 401, 9A Uniform Laws Annot. § 401(d) at 550 (1987 Master Ed.). Colorado was the first of only eight states to adopt the Uniform Act.

The pertinent portions of the Dissolution Act are now codified at § 14-10-123, C.R.S. (1987 Repl. Vol. 6B), as follows:

(1) A child custody proceeding is commenced in the district court or as otherwise provided by law:

(a) By a parent:

. . . or

(b) By a person other than a parent, by filing a petition seeking custody . . . but only if the child is not in the physical custody of one of his parents . . . .

The commissioner's comment concerning this provision of the Uniform Act explains that:

[S]ubsection (d)(2) [adopted verbatim by the Colorado General Assembly in 1971 and now codified as § 14-10-123(1)(b)] makes it clear that if one of the parents has physical custody of the child, a non-parent may not bring an action to contest that parent's right to continuing custody under the 'best interest of the child' standard . . . .

Uniform Marriage and Divorce Act § 401, 9A Uniform Laws Annot. at 550 (Master Ed. 1987) (Commissioner's Comment).

The term "physical custody" is not defined either in the Uniform Act or in the Dissolution Act. In other states that have adopted § 401(d) of the Uniform Act, appellate courts have interpreted the term "physical custody" to mean something more than physical possession of the child. See Webb v. Charles, 125 Ariz. 558, 611 P.2d 562 (Ariz.Ct.App. 1980) (relinquishment of parental legal rights a prerequisite to divesting parent's right of physical custody for purposes of standing to commence custody proceeding); In re Custody of McCuan, 176 Ill. App.3d 421, 531 N.E.2d 102 (1988) (child's visiting grandparents with mother's consent insufficient to divest mother of physical custody of child); Henderson v. Henderson, 568 P.2d 177 (Mont. 1977) (because natural mother never relinquished her parental rights, child's aunt, who had physical possession following natural father's death, lacked standing to bring a custody proceeding).

In 1973, the Colorado statute was amended by the addition of a new subsection, now codified at § 14-10-123(1)(c), C.R.S. (1987 Repl. Vol. 6B). Under that amendment, a custody proceeding may be commenced:

By a person other than a parent who has had physical custody of a child for a period of six months or more, if such action is commenced within six months of the termination of such physical custody.

See Colo. Sess. Laws 1973, ch. 162, § 46-1-23(1)(d) at 554.

In enacting § 14-10-123(1)(c), the Colorado General Assembly has indicated its preference for a more literal meaning of the phrase "physical custody." Under that section, a non-parent having had physical custody of a child for six months or more is granted standing to commence proceedings for legal custody of such child so long as such proceedings are begun within six months after the physical custody has ended.

The adoption of this section constitutes legislative recognition of the effects of "psychological parenting" upon the best interests of a child. See also § 19-3-702(5)(b), C.R.S. (1993 Cum. Supp.) (recognizing need for custodial stability and permanency planning for children adjudged dependent or neglected and removed from physical custody of their parents without terminating the parent-child relationship). It also makes clear that the Colorado General Assembly did not intend to equate "physical custody" with either "legal custody" or the "parental right to continued physical or legal custody."

Other provisions of the Dissolution Act, while not defining the term "physical custody," are also instructive as to its meaning. For example, the term "shared physical custody" as applied to parents for purposes of calculating child support means each parent keeping the child for a specified minimum number of overnight stays each year and contributing to the child's expenses in addition to payment of child support. Section 14-10-115(8), C.R.S. (1993 Cum. Supp.).

Similarly, § 14-10-123.5(1), C.R.S. (1987 Repl. Vol. 6B) clearly separates the concepts of parental physical and legal custody of children in dissolution or separation proceedings. Legal custody may be awarded under that section jointly to both parents simultaneously with awards of unequal physical custodial rights to the respective parents.

In addition, in § 14-13-103(9), C.R.S. (1987 Repl. Vol. 6B), Colorado's enactment of the Uniform Child Custody Jurisdiction Act, the term physical custody is defined as "actual possession and control of a child."

We thus conclude, consistent with the views expressed in other Colorado decisions under the Dissolution Act, that, in adopting § 19-10-123(1)(b), our General Assembly intended that a literal meaning be applied to the term "physical custody" in adopting § 14-10-123(1)(b). Hence, in keeping with the overriding policy of promoting the best interests of children, Colorado has adhered to a liberalized view as to the standing of non-parents to commence and to participate in custody proceedings. See Abrams v. Connolly, 781 P.2d 651 (Colo. 1989); In re Marriage of Dureno, 854 P.2d 1352 (Colo.App. 1992); In re Marriage of Trouth, 631 P.2d 1183 (Colo.App. 1981); In re Marriage of Tricamo, 42 Colo. App. 493, 599 P.2d 273 (1979).

We reject the mother's argument that only step-parents or blood relatives of the child or his parents should be accorded standing as "person[s] other than a parent" under § 14-10-123(1)(b) and (c). The fact that reported cases involved such persons is attributable to the fact that, in our society, persons are more likely to develop an interest in, or a relationship with, children of relatives than with children of strangers. However, we find no language in the statute or in any Colorado appellate decision to indicate that such relationship is a legal requirement for non-parent standing to commence custody proceedings.

Likewise, we are unpersuaded by the argument that a liberalized view of non-parent standing to commence custody actions will serve to reward persons who obtain physical custody over children by criminal, fraudulent, or other forms of misconduct. Under the Colorado statutory scheme, consideration of evidence of such misconduct has been left to the discretion of trial courts in determining the best interests of children on an ad hoc basis, rather than by imposition of an arbitrary and inflexible rule of standing. We believe it unlikely that a trial court would find it in a child's best interest to award custody to a person who had obtained physical custody by kidnapping, fraud, or other overreaching conduct.

II.

The mother also contends that § 14-10-123(1)(b) cannot be used as a vehicle to obtain custody of a child who has been placed by a parent with non-parents in contemplation of relinquishment and adoption proceedings. We disagree.

Here, the mother's consent to placement upon the birth of her child was not found to be involuntary or the result of fraud or overreaching by petitioners. Rather, the placement was made upon the mother's expressed belief that it was in the child's best interests.

Although the placement was initially made in contemplation that it would be followed by relinquishment and adoption proceedings under the Colorado Children's Code, such proceedings later became impossible when the mother withdrew her consent thereto and did not honor her agreement to obtain counseling as required by § 19-5-101, et seq., C.R.S. (1993 Cum. Supp.). In so doing, the mother acted within her legal rights and thereby prevented the initiation of the proceedings to which she had previously consented.

Consequently, since no proceedings were ever commenced under the Children's Code for relinquishment or adoption of C.C.R.S., custody proceedings under the Dissolution Act were not preempted by the provisions of §§ 19-1-104(1)(c), 19-1-104(4), or 19-1-104(5), C.R.S. (1993 Cum. Supp.). See Johnson v. Black, 137 Colo. 119, 322 P.2d 99 (1958); cf. People in Interest of D.C., 851 P.2d 291 (Colo.App. 1993).

Moreover, although the mother advised petitioners' counsel that she desired to withdraw her consent to relinquishment and adoption and to regain custody of C.C.R.S., the record before us does not suggest that she took any steps to regain physical custody of the child at that time. Indeed, she did not personally appear or otherwise present evidence at the temporary custody hearing held on October 30, 1990. According to the record before us, the mother's own cross-petition for custody of C.C.R.S. was first filed with the district court on or about June 17, 1991, after the child had been in the physical custody and control of petitioners for over one year.

Furthermore, there is no evidence that C.C.R.S. has ever been in the mother's physical custody since his birth. There was evidence that, despite an agreement for continued visitation and contact between the mother and C.C.R.S. during his placement with petitioners, mother has made little or no effort to establish a relationship with the child. In fact, the record reflects that, by the date of the final district court hearing, the mother had visited the child on only two brief occasions since his birth, despite being awarded the right of visitation in the magistrate's temporary custody order.

Under these circumstances, not only does § 14-10-123 permit proceedings for custody by petitioners, but the best interests of the child strongly dictate resolution of the competing interests of the natural and psychological parents in whatever adjudicative forum was then available for determination of such issues.

III.

In support of her contention as to petitioners' lack of standing under § 14-10-123(1)(b) and her argument that the trial court erred in using the best interests standard rather than requiring petitioners to prove parental unfitness before terminating her custodial rights, the mother relies upon several decisions from the United States Supreme Court that recognize a fundamental constitutional liberty interest in the preservation of parental rights of care, custody, and control of their children. We conclude that such reliance is misplaced under the circumstances presented here.

Initially, we note that the mother's contentions on appeal include constitutional arguments that are not addressed in the trial court's findings, conclusions, and custody order. In addition, the limited record on appeal does not indicate whether such arguments were raised in the trial court proceedings.

Generally, appellate courts will not consider issues, arguments, or theories not previously presented in trial proceedings. Matthews v. Tri-County Water Conservancy District, 200 Colo. 202, 613 P.2d 889 (1980).

Here, however, the mother argues that her fundamental liberty interest in her parent-child relationship with C.C.R.S. limits or precludes both the custody proceedings and the resulting order. Hence, since issues concerning fundamental constitutional rights have been asserted and fully briefed and argued by all parties on appeal, and since the ultimate issue relating to custody of a minor child requires an expedited resolution, we elect to address such arguments in this appeal. See Robinson v. People, 173 Colo. 113, 476 P.2d 262 (1970); In re Marriage of Trouth, supra.

In Stanley v. Illinois, 405 U.S. 645, 92 S.Ct. 1208, 31 L.Ed.2d 551 (1972), the court upheld the interest of an unwed natural father to be accorded notice and a due process hearing as to his fitness before terminating his parental rights in dependency proceedings commenced after the death of the children's mother. In holding unconstitutional an Illinois statute which presumed the father of illegitimate children to be unfit, the court observed that the effect of that statute was to eliminate automatically an unwed father's parental rights in violation of his rights of due process and equal protection under the law.

Here, unlike the circumstances in Stanley, these were not dependency proceedings instituted by the state which will result in termination of the mother's parental rights. In addition, the mother was afforded notice and an opportunity for hearing to determine her right to custody of C.C.R.S.

In Quilloin v. Walcott, 434 U.S. 246, 98 S.Ct. 549, 54 L.Ed.2d 511 (1978), the court held that the parental rights of a father who had never sought or had physical or legal custody of a child could be terminated in a step-parent adoption proceeding by application of a best interest standard rather than upon a finding of unfitness as to the father. There, the court noted that, while the father had not abandoned the child, he had not undertaken any significant responsibility for its rearing, nor had he attempted to legitimize the child pursuant to Georgia law during the eleven years of the child's life prior to the filing of the step-father's petition for adoption. The court also noted that this was not an attempt by the state or the adoptive parents to break up a natural family; but rather was a recognition of a de facto family unit already in existence. The court held that, under those circumstances, the state was not required to find more than that the adoption and the denial of the legitimization was in the best interests of the child.

In Santosky v. Kramer, 455 U.S. 745, 102 S.Ct. 1388, 71 L.Ed.2d 599 (1982), the court held that a "clear and convincing evidence" standard of proof was required in a state's parental rights termination proceeding. There, the court noted that, because the nature of termination is final, permanent, and irrevocable as to all parental rights, a heightened burden of proof is necessary in order to comport with the requirements of due process. See also People in Interest of E.A., 638 P.2d 278 (Colo. 1982).

Here, unlike the terminations contemplated in Santosky and E.A., the mother's parental rights were not subject to full, final, and irrevocable severance in custody proceedings pursuant to § 14-10-123. She maintained a right to have continuing contact and visitation or parenting time with the child and, upon appropriate changed circumstances, to move for and possibly be awarded custodial rights, in addition to her preserved residual parental rights.

In Lehr v. Roberts, 463 U.S. 248, 103 S.Ct. 2985, 77 L.Ed.2d 614 (1983), the court upheld a New York statute that permitted a father of an illegitimate child to claim paternity by filing a notice of his intent to do so in a state putative father registry. Upon so registering, a father became entitled to notice of any adoption proceedings concerning the child. A father who had not so registered argued that the statute was violative of his right of due process arising from his fundamental liberty interest in his two-year-old illegitimate daughter.

The U.S. Supreme Court once again recognized the difference between a developed parent-child relationship and one in which the natural parent had never demonstrated a commitment to the responsibilities of parenthood by coming forward to participate in the rearing of the child. The court noted that the father never had a significant custodial, personal, or financial relationship with the child and did not seek to establish any legal tie until his daughter was two years old. In rejecting the father's appeal, the court held that New York's process under the registry statute was sufficient to satisfy the rights arising from such an undeveloped parent-child relationship.

Our review of these authorities convinces us that, since this case does not involve termination or relinquishment of parental rights nor their abrogation by adoption, due process does not require a showing of parental unfitness or the use of an enhanced standard of proof.

Here, the trial court recognized the general rule that a biological parent is ordinarily entitled to have the first and prior right to custody of her child, and it indulged a presumption to that effect. However, that presumption may be rebutted by evidence establishing that the welfare of the child would be promoted by awarding custody to a non-parent. See Abrams v. Connolly, supra.

We conclude, therefore, that the trial court did not err in determining that petitioners had standing to proceed under the provisions of § 14-10-123, in determining the issue of custody under the best interests of the child standard, or in refusing to require a showing of the mother's parental unfitness.

The order is affirmed.

JUDGE DAVIDSON concurs.

JUDGE TAUBMAN dissents.