Implied Consent Opens the Door: Montana Supreme Court Affirms Post‑Trial Amendment and Third‑Party Parental Interest Under § 40‑4‑228, MCA

Case: In re the Marriage of Rehbein and Paddock (2025 MT 201, DA 25‑0031)

Court: Supreme Court of Montana

Decision Date: September 9, 2025

Author: Justice James Jeremiah Shea (McKinnon, J., concurring; Swanson, C.J., concurring)

Introduction

This decision addresses two recurring, high‑stakes issues at the intersection of family law and civil procedure in Montana: (1) when a court may amend pleadings after trial to conform to the evidence under M. R. Civ. P. 15(b)(2), and (2) what evidence suffices to award a nonparent a “parental interest” under § 40‑4‑228, MCA, commonly called third‑party parenting. The Court affirms a district court decree awarding parental rights to a nonbiological spouse in a same‑sex marriage based on clear and convincing evidence of a child‑parent relationship and the children’s best interests, despite the fact that the operative pleadings principally invoked a different parentage statute.

Beyond its immediate holding, the case underscores two major themes: Montana trial courts may reach the merits of third‑party parenting claims if the issue was actually tried by the parties’ consent—even without formal amendment before judgment—and robust, record‑based findings will be sustained on appeal. In concurring opinions, the Justices also surface (but do not resolve) a significant statutory question: whether the presumption of parentage in § 40‑6‑105, MCA, applies in the same way to a nonbiological spouse in a same‑sex marriage.

Background and Key Issues

Ciara Lynn Rehbein and Jessica Michelle Paddock married in 2014, divorced in 2017, rekindled their relationship, and remarried in 2018. During the relationship and second marriage, two children were born to Rehbein via sperm donors: A.M.R. (born July 29, 2018) and M.J.R. (born October 18, 2021). Paddock was initially listed as the “father” on A.M.R.’s birth certificate but was later removed in 2020 after she filed an affidavit of non‑paternity—an action she testified was intended to facilitate a formal adoption that never occurred. The parties separated in February 2022, but Paddock continued regular caregiving.

When dissolution proceedings commenced, Rehbein’s petition stated there were no children; Paddock counter‑petitioned, asserting that the children were of the marriage and seeking a parenting plan. She later petitioned for a determination of parentage under § 40‑6‑105, MCA (presumptive parentage). After a multi‑day bench trial (December 8, 2023; July 11–12, 2024), the district court awarded Paddock a parental interest under § 40‑4‑228, MCA, entering a parenting plan. On appeal, Rehbein challenged two rulings:

• Whether the district court erred by amending the pleadings after trial to consider § 40‑4‑228, MCA, under Rule 15(b)(2); and
• Whether the district court erred on the merits in granting Paddock a parental interest under § 40‑4‑228, MCA.

Paddock cross‑appealed the district court’s denial of a presumption of parentage under § 40‑6‑105, MCA, including constitutional arguments; the Supreme Court declined to reach those issues, resolving the case under § 40‑4‑228, MCA.

Summary of the Opinion

• Pleadings amended by implied consent: The Court held the district court did not abuse its discretion by amending the pleadings after trial to conform to the evidence and to consider § 40‑4‑228, MCA. The record showed the issue was tried by implied consent: Paddock explicitly referenced the “third‑party parenting statute” during her case‑in‑chief; both parties presented evidence relevant only to that theory; Rehbein failed to object that the evidence was beyond the pleadings; and the months‑long gap between the first and second trial days afforded ample time to prepare and respond.
• Parental interest affirmed: The Court affirmed the award of a parental interest under § 40‑4‑228, MCA. Applying a clear‑error standard to the district court’s factual findings, the Court concluded substantial evidence supported each element: (a) Rehbein engaged in conduct contrary to the parent‑child relationship (including sobriety struggles and regularly, voluntarily delegating parental care to Paddock); (b) Paddock established a child‑parent relationship as defined in § 40‑4‑211, MCA; and (c) continuation of that relationship is in the children’s best interests. The Court declined to reweigh conflicting evidence.
• Concurrences: Justice McKinnon would have recognized a presumption of parentage for Paddock under § 40‑6‑105(1)(a), MCA, based on the statute’s gender‑neutral term “person” and traditional rules of construction. Chief Justice Swanson disagreed, cautioning that § 40‑6‑105 is ill‑suited for nonbiological same‑sex spouses and endorsing the district court’s reliance on § 40‑4‑228, MCA.

Analysis

Precedents Cited and Their Influence

• M. R. Civ. P. 15(b)(2) (Implied consent; amendment to conform to evidence). The Court relied on established Montana authority that issues not pleaded may be treated as if pleaded when tried by the parties’ express or implied consent. Failure to amend formally does not affect the outcome when the issue has been tried.
• Watters v. City of Billings, 2019 MT 255 and Armbrust v. York, 2003 MT 36: These cases frame the implied‑consent inquiry, emphasizing that consent can be found where the parties were on notice that the issue was being tried and had a fair opportunity to address it. The interaction of factors—including acquiescence to evidence and lack of prejudice—governed the analysis here.
• Hjartarson v. Hjartarson, 2006 MT 273: Consent may be implied where a party does not object to evidence extrinsic to the pleadings. The Court noted Rehbein did not object on scope grounds when § 40‑4‑228‑specific evidence was introduced, even when raising other evidentiary objections.
• In re Custody of C.J.K., 258 Mont. 525 (1993): The appellant’s principal authority. The Supreme Court distinguished it on two fronts: (1) timing—there, a new custody theory was introduced mid‑trial after the mother’s case‑in‑chief; here, the third‑party parenting theory was raised during Paddock’s initial presentation; and (2) prejudice—there, the mother promptly sought a continuance for surprise; here, the trial was continued for seven months, and no analogous motion was made.
• Kulstad v. Maniaci, 2009 MT 326: A cornerstone of Montana third‑party parenting jurisprudence. The Court leaned on Kulstad for standards of review and deference to the trial court’s credibility findings in nonparent custody disputes. Kulstad’s admonition against appellate reweighing of conflicting testimony featured prominently.
• Sayler v. Yan Sun, 2023 MT 175: Cited for standards of review and as a cautionary contrast: where a district court fails to analyze § 40‑4‑228’s elements, reversal may be required. Here, the district court’s findings tracked the statutory elements and were supported by the record.
• Glacier Nat’l Bank v. Challinor, 253 Mont. 412 (1992): Reinforces the abuse‑of‑discretion standard for amending pleadings to conform to the evidence.
• Davis v. Davis, 2016 MT 52: Applied for the principle that courts avoid constitutional questions if cases can be decided on non‑constitutional grounds, thereby bypassing constitutional challenges to § 40‑6‑105, MCA.

Legal Reasoning

1) Amending Pleadings by Implied Consent (Rule 15(b)(2))

The Court accepted the district court’s application of Rule 15(b)(2) because the evidentiary record showed the § 40‑4‑228 issue was tried in substance:

• Paddock flagged her “alternative pleading” under the “third‑party parenting statute” during her case‑in‑chief on day one of trial.
• Both sides then presented extensive evidence that made sense only under § 40‑4‑228—such as whether Rehbein engaged in conduct contrary to the parent‑child relationship, whether Paddock stood in loco parentis, and whether continuation of the relationship served the children’s best interests.
• Rehbein did not object that this evidence was beyond the scope of the pleadings and secured a lengthy continuance, which undercut claims of unfair surprise.

Distinguishing Custody of C.J.K., the Court emphasized that implied consent fails when a new issue is sprung mid‑trial without fair opportunity to respond; here, the opposite occurred. The procedural posture and the parties’ conduct supported amendment to conform to the issues actually tried.

2) Awarding a Parental Interest Under § 40‑4‑228, MCA

Section 40‑4‑228, MCA, authorizes awarding a “parental interest” to a nonparent if the nonparent proves by clear and convincing evidence that:

• The parent engaged in conduct contrary to the child‑parent relationship;
• The nonparent established a child‑parent relationship (as defined by § 40‑4‑211, MCA); and
• Continuation of that relationship serves the child’s best interests.

Applying a clear‑error standard to the district court’s findings, the Supreme Court affirmed:

• Contrary conduct: The district court found that Rehbein “consistently engaged in conduct contrary to the parent‑child relationship” due to sobriety struggles, concerning parenting practices, and by “regularly and voluntarily” allowing Paddock to assume primary caregiving—placing Paddock in loco parentis.
• Child‑parent relationship: Evidence showed Paddock provided physical care, financial support, companionship, and stability since the children’s births. She was listed as a parent on medical/insurance records, and the parties’ joint tax returns (2018–2021) claimed the children as dependents with Paddock as the primary taxpayer.
• Best interests: Multiple witnesses described Paddock as a stable, loving caregiver; the children enjoyed their time with her; and the court found she exercised good judgment in prioritizing their safety and welfare.

Although Rehbein highlighted conflicting testimony (including from her mother and certain therapists or relatives), the Court reiterated that credibility determinations belong to the trial court, which observed the witnesses firsthand. The presence of conflicting evidence does not negate substantial evidence supporting the findings.

Impact and Forward‑Looking Consequences

Procedural Impact

• Rule 15(b)(2) in family cases: Montana trial courts have clear permission to reach unpleaded third‑party parenting claims when the evidence and trial conduct show the issue was actually tried by implied consent and without unfair surprise. Practitioners cannot assume that a narrow pleading will cabin the case if both sides litigate broader issues at trial.
• Timely objections matter: Failure to object that evidence lies beyond the pleadings, especially when coupled with a long continuance to prepare, undermines later complaints of prejudice. Litigants seeking to preserve a scope objection should raise it contemporaneously and, if needed, seek a continuance immediately.

Substantive Family Law Impact

• Roadmap for nonbiological co‑parents: The opinion reinforces that § 40‑4‑228, MCA, remains a viable avenue for nonbiological caregivers—often same‑sex spouses or partners—to establish parental rights where they have functioned as a parent and continuation of that relationship serves the child’s best interests.
• In loco parentis and contrary conduct: Regular and voluntary delegation of parental responsibilities to a nonparent, coupled with evidence of instability (e.g., substance‑abuse‑related concerns), can satisfy the “contrary conduct” prong when the nonparent has stepped into a true parenting role.
• What evidence persuades: Documentary markers (insurance designations, tax returns, birth‑related involvement) plus consistent care and credible third‑party testimony carry significant weight in proving a child‑parent relationship and best interests.

Unresolved Question: Presumption of Parentage Under § 40‑6‑105, MCA

Justice McKinnon’s concurrence posits that § 40‑6‑105(1)(a), MCA—which uses the gender‑neutral term “person” and, by rule, includes the feminine—confers a presumption of parentage on a spouse when a child is born during the marriage, regardless of sex. She underscores:

• Plain‑language interpretation principles (City of Missoula v. Fox; State v. Alpine Aviation);
• Statutory directives favoring natural rights and gender‑neutral construction (§ 1‑2‑104, MCA; § 1‑2‑105(2), MCA);
• Historical amendments replacing “man/he” with “person” (1995 Mont. Laws ch. 418).

Chief Justice Swanson’s concurrence cautions the presumption is historically tailored to disputes involving a husband’s biological paternity versus another man’s, rendering it ill‑fit for nonbiological same‑sex spouses. The majority does not resolve this tension, leaving a meaningful statutory interpretation question for future cases or legislative clarification.

Complex Concepts Simplified

• Implied consent (Rule 15(b)(2)): Even if a legal theory isn’t pleaded, if both sides actually try the issue—by introducing and not objecting to evidence that only makes sense for that issue—the court may treat the pleadings as if they included it. Formal amendment is optional if the issue was tried.
• Clear and convincing evidence: A higher burden than “more likely than not,” requiring that the evidence makes the facts highly probable, though not beyond all doubt.
• Child‑parent relationship (§ 40‑4‑211, MCA): A relationship formed through sustained caregiving, guidance, support, and emotional bonding—functionally acting as a parent in the child’s life.
• Conduct contrary to the child‑parent relationship: Parental behaviors that undermine the parent’s role or the child’s welfare (e.g., persistent instability, substance abuse) or voluntarily ceding day‑to‑day parenting to a nonparent who then stands in loco parentis.
• In loco parentis: A nonparent who has assumed the obligations and role of a parent in practice.
• Standards of review:
  • Abuse of discretion: Deferential; used for procedural rulings like amending pleadings.
  • De novo: Fresh look; used for legal questions.
  • Clear error: Deferential to trial courts on fact‑finding; the appellate court does not reweigh witness credibility.

Practical Guidance for Future Cases

• Plead broadly and in the alternative: Family‑law litigants seeking nonparent rights should expressly plead § 40‑4‑228, MCA, in addition to any presumptive parentage or adoption claims. Doing so obviates Rule 15 disputes.
• Build a documentary record: Insurance and medical forms listing the nonparent as a parent, tax returns claiming children as dependents, and consistent involvement around births and childcare are highly persuasive.
• Preserve scope objections: If opposing evidence ventures beyond the pleadings, object on scope and, if needed, immediately seek a continuance to avoid implied consent.
• Expect deference on appeal: Because credibility findings and best‑interests assessments receive substantial deference, the trial record is paramount.
• Watch the parentage‑presumption issue: The concurring opinions signal that whether § 40‑6‑105(1)(a), MCA, confers a presumption on a nonbiological spouse in a same‑sex marriage remains open at the Supreme Court level.

Conclusion

Marriage of Rehbein and Paddock cements two important propositions in Montana family law. First, under Rule 15(b)(2), trial courts may amend pleadings after trial to reach third‑party parenting claims when the issue was actually tried by implied consent, with no unfair surprise—ensuring substance prevails over form when the evidence and fairness so warrant. Second, the Court reaffirms that a robust, well‑documented caregiving history—coupled with proof of contrary parental conduct and best interests—will sustain an award of parental interest to a nonparent under § 40‑4‑228, MCA.

While the Court sidesteps the constitutional and statutory debate over presumptive parentage in § 40‑6‑105, MCA, the concurrences illuminate a live question for future litigation or legislative action. In the meantime, this opinion offers clear guidance on the evidentiary showings and procedural pathways through which dedicated nonbiological caregivers—particularly in same‑sex relationships—can secure legally recognized parental roles in Montana.