Leonard, Street and Deinard, Professional Association, Respondent, vs. American Agri-Technology Corporation, Appellant.

may not be cited except as provided by

Minn. Stat. § 480 A. 08, subd. 3 (1996).

 STATE OF MINNESOTA

 IN COURT OF APPEALS

 C8-98-1013

In Re the Marriage of:

Catherine Mary Workman, petitioner,

Appellant,

vs.

Martin Donald Workman,

Respondent.

 Filed November 3, 1998

 Affirmed
Foley, Judge*

 Dakota County District Court

 File No. F7-96-13531

William Christopher Penwell, 1300 Washington Sq., 100 Washington Ave. S., Minneapolis, MN 55401 (for appellant)

Robert J. Lawton, 1100 West 7th St., St. Paul, MN 55102 (for respondent)

Considered and decided by Peterson, Presiding Judge, Randall, Judge, and Foley, Judge.

 U N P U B L I S H E D   O P I N I O N

 FOLEY, Judge

Appellant Catherine M. Workman challenges the district court's denial of her motion for custody modification. Appellant argues that the court erred in not finding that the current joint physical custody arrangement endangers the physical and emotional health of the children and that the district court erred when it excluded polygraph examination results from evidence. We affirm.

FACTS

Catherine Workman and respondent Martin Workman were married in 1991 and had two children; a son born in 1993 and a daughter born in 1995. The marriage was dissolved on April 1, 1997. The parties were granted joint legal and physical custody.

Appellant alleged that on October 3, 1997, their daughter complained to her that her "potty hurt." After noticing that the daughter's genitals were red, appellant asked her how she had received the "owie," to which the daughter reportedly replied, "Daddy's finger." Appellant then took the daughter to the emergency room. The physician who examined her there found no evidence of sexual abuse, and she was ultimately diagnosed with a bladder infection. Appellant's sister and the daughter's daycare provider also reported that the daughter had made statements to them about respondent touching her genitals and hurting her. Appellant kept a journal in which she documented similar statements that the daughter allegedly made during the months of October and November. Hennepin County Child Protection and the Richfield Police Department investigated the abuse allegations and were unable to substantiate the abuse.

Appellant brought the daughter to see a therapist. The therapist did a child-sexual- behavior checklist and a touch-contemporaneous format with the daughter. The therapist found the daughter showed no negative or inappropriate behaviors and determined that she showed no symptoms of being abused.

On December 26, 1997, appellant filed her motion for modification of the custody order, seeking sole physical custody and supervised visitation for respondent. Appellant alleged that later that evening her son told her that his "potty" hurt. Appellant asked how he had been hurt and he reportedly replied, "Daddy touches my potty." The next day appellant took her son to the emergency room where he was examined. No evidence of physical abuse was found. Upon recommendation of the emergency room personnel, appellant brought her son to Children's Hospital the following day. There he underwent a videotaped interview with Ms. Mauer, a Suspected Child Abuse Nurse. During the interview, he repeated that respondent had touched him on his "pee pee" under his pajamas while in respondent's bedroom. The son also stated that he had seen respondent touch the daughter on her "potty." Ms. Mauer testified that, while it is difficult to know whether a child has been coached, she had no reason not to believe what the son had told her.

The son was also brought to see the therapist, who found that he did not show the symptoms of an abuse victim. The son's preschool teacher testified that she had taught children who had been victims of sexual abuse and that the son did not display any of the symptoms she had seen displayed by those abuse victims.

This allegation of sexual abuse resulted in new investigations by the Richfield Police Department and by Hennepin County Child Protection. During the course of the investigation, respondent voluntarily submitted to a polygraph examination as arranged by the police. At the completion of their investigations both agencies closed their files without bringing any charges.

Appellant sought to have the results of the polygraph examination admitted into evidence. The district court excluded the polygraph results by order dated March 9, 1998.

An evidentiary hearing was held on the motion for custody modification. The district court denied the motion for custody modification by order dated April 1, 1998, finding that the allegations of abuse had not been substantiated. Both parties moved for amended findings. Those motions were denied and this appeal followed.

D E C I S I O N

1. Custody Modification

An appellate court will not reverse a custody determination unless the district court abused its discretion by making findings unsupported by the evidence or by improperly applying the law. Pikula v. Pikula, 374 N.W.2d 705, 710 (Minn. 1985). A district court's findings will be sustained unless they are clearly erroneous. Id.

  Modification of child custody orders is governed by Minn. Stat. § 518.18 (1996).

If the court has jurisdiction to determine child custody matters, the court shall not modify a prior custody order unless it finds, upon the basis of facts, including unwarranted denial of, or interference with, a duly established visitation schedule, that have arisen since the prior order or that were unknown to the court at the time of the prior order, that a change has occurred in the circumstances of the child or the parties and that the modification is necessary to serve the best interests of the child. In applying these standards the court shall retain the custody arrangement established by the prior order unless:

* * *

(iii) the child's present environment endangers the child's physical or emotional health or impairs the child's emotional development and the harm likely to be caused by a change of environment is outweighed by the advantage of a change to the child.

Minn. Stat. § 518.18(d). The procedures for modification of custody reflect the legislature's preference for permanence and closure on custody matters, except under the most extraordinary circumstances where changed circumstances endanger the child's physical or emotional health. Silbaugh v. Silbaugh, 543 N.W.2d 639, 642 (Minn. 1996); see also Ross v. Ross, 477 N.W.2d 753, 756 (Minn. App. 1991) (legislature "likely intended to demand a showing of a significant degree of danger").

Appellant argues that there was significant evidence presented proving endangerment and that the district court ignored the relevant evidence in its findings. Specifically, appellant points to the evidence of sexual abuse provided by the testimony of appellant, her sister, the nurse, and the daycare provider, as well as the videotaped interview of the boy and the journal kept by appellant. Appellant stresses that the district court made no findings regarding the credibility of these witnesses or the reliability of the evidence.

District courts "stand in a superior position to appellate courts in assessing the credibility of witnesses." In re Welfare of M.D.O., 462 N.W.2d 370, 374-75 (Minn. 1990). The district court's superior ability to assess witness credibility is "particularly true" where the court's

opportunity to observe the parent and other witnesses who are called to testify is so crucial to an accurate evaluation of what is best for the child.

In re Welfare of A.D., 535 N.W.2d 643, 648 (Minn. 1995).

The district court had conflicting evidence before it. In contrast to the evidence in support of an endangerment finding, there was evidence that the children's therapist did not find the children to have symptoms typical of abuse victims. There was further evidence that the son's preschool teacher did not see him behave like other sexual abuse victims with whom she had worked. In contrast to appellant's assertion that her son was depressed, the teacher testified that the boy appeared happy and well-adjusted. Although the district court did not explicitly find that appellant's witnesses were not credible, it stated in its memorandum that appellant's

evidence lies solely in statements, which she alleges the minor children to have made to her and her family members. However, the Court finds that these statements are unsubstantiated. All neutral participants in this matter, including police officers, physicians, therapists, social workers and a teacher, have not been able to substantiate the abuse. To the contrary, these neutral observers have found that neither child displays signs of abuse and both children appear to be happy and well-adjusted. Furthermore, [appellant] has failed to offer any evidence by an unbiased witness that [the boy or girl] fear or dislike Respondent in any way. The unbiased witnesses who did testify, including [the boy's] Pre-school Teacher and the guardian ad litem, found the children displayed a strong bond and affection with Respondent and were clearly not afraid of Respondent.

We recognize that there is a great deal of hostility and emotion involved here, but the matter has been heard by the district court and it is not the place of this court to substitute our judgment for that of the district court. The district court's finding that the abuse was unsubstantiated is not clearly erroneous and the decision to deny appellant's request for sole physical custody was well within the court's discretion.

2. Polygraph Evidence

The decision to admit or exclude evidence rests within the broad discretion of the district court and its ruling will not be disturbed unless it is based on an erroneous view of the law or constitutes an abuse of discretion. Uselman v. Uselman, 464 N.W.2d 130, 138 (Minn. 1990). It is well established that polygraph examination results are inadmissible in Minnesota civil and criminal actions. State v. Anderson, 379 N.W.2d 70, 79 (Minn. 1985), cert. denied, 476 U.S. 1141 (1986) (citing State v. Michaeloff, 324 N.W.2d 926, 927 (Minn. 1982)).

Appellant, while acknowledging that polygraph results are not admissible in Minnesota, argues that this court should extend the law to allow the introduction of such evidence. However, "[t]he function of the court of appeals is limited to identifying errors and then correcting them." Sefkow v. Sefkow, 427 N.W.2d 203, 210 (Minn. 1988) (citations omitted). "The task of extending existing law falls to the supreme court or the legislature, but it does not fall to this court." Tereault v. Palmer, 413 N.W.2d 283, 286 (Minn. App. 1987), review denied (Minn. Dec. 18, 1987). Regardless of whether appellant's policy arguments have merit, the district court did not abuse its discretion in excluding respondent's polygraph results from evidence.

Affirmed.

* Retired judge of the Minnesota Court of Appeals, serving by appointment pursuant to Minn. Const. art. VI, § 10.