dissenting.
A review of the record, the pleadings and oral argument before this Court make it clear that Theron’s sexual orientation was wrongfully taken into consideration by the lower court and now the majority opinion. This should not be the law of Idaho and is *655undesirable public policy. Therefore, I respectfully dissent.
The Idaho law regarding custody modification is well established. Custody may not be modified unless there is a material, permanent and substantial change in circumstances that indicate that modification is in the best interests of the children. Tomlinson v. Tomlinson, 93 Idaho 42, 47, 454 P.2d 756, 761 (1969). Shawn asserts that Theron’s sexual orientation is a substantial change in circumstances. Her petition states, “events have occurred with respect to the Defendant’s intimate relationship with a person of the same sex which have completely changed the circumstances, such that it is no longer in the best interests of the girls that they spend one-half of the overnights each week with the Defendant.” Although it is clear that Shawn’s petition is based on Theron’s homosexuality, the majority upholds the magistrate’s decision, which clearly appears to take Theron’s homosexuality into consideration. Immediately after stating that homosexuality did not play a role in its holding, the magistrate stated, “However, [Theron’s] decision to openly co-habit with Nick Case, his partner, is a change in circumstances which will generate questions from the girls and their friends regarding their conservative culture and morays (sic) in which the children live.”
The magistrate sets forth several reasons why its decision to review custody was warranted, including the following, which were not included in Shawn’s petition:
• The girls’ current difficulty and adjustment in changing residence each Wednesday;
• Theron’s impending move and change of schools for one of the children; and
• Theron’s continuing refusal to communicate directly with Shawn and to allow her to participate in important communications and decisions regarding the girls.
The majority interestingly argues that the Court is not confined by the allegations of the petition when deciding what custody arrangement is in the best interests of the children, so it is insignificant that these reasons were not included in the petition. However, it is unusual and cause for legal concern, that the magistrate reached for reasons to help Shawn succeed in her claim when the primary reason stated in her petition to modify custody, homosexuality, is not a legally permissible consideration.
In addition to giving Shawn primary custody of the girls, the majority upholds the decision to limit Theron’s visitation “provided [Theron] is not residing in the same house with his male partner.” If Theron’s sexual orientation is not a factor, it is disingenuous that Theron may only exercise his visitation rights if he does not live with his male partner. The majority somewhat incredulously states that the limitation has nothing to do with Theron’s homosexuality, rather it is a consequence of hang-up phone calls allegedly made by Theron’s partner to Shawn.
Although courts are not bound by expert testimony, it is very persuasive in eases of this nature that the district court-appointed custody evaluator, Dr. Corgiat, recommended that the approximate 50-50 shared custody arrangement remain unchanged. He noted that, “[B]oth children have a positive relationship with each parent and with each other. Both parents have shown positive nurturing, and have spent quality time in a variety of good activities with the girls.”
While the determination to modify child custody is left to the sound discretion of the trial court, this Court may substitute its judgment and discretion for that of the trial court when the record reflects a clear abuse of discretion. Biggers v. Biggers, 103 Idaho 550, 555, 650 P.2d 692, 697 (1982). An abuse of discretion can occur if the trial court misapplies the law or fails to reach its decision by an exercise of reason. Sun Valley Shopping Center v. Idaho Power, 119 Idaho 87, 94, 803 P.2d 993, 1000 (1991). The record reflects an abuse of discretion since Theron’s sexual orientation was wrongfully taken into consideration; therefore, the decision of the magistrate should be reversed.