The standard of review the Supreme Court applies in appellate cases identifies the level of deference the Court must accord a district court's decision. Cole v. Valley Ice Garden, L.L.C., 2005 MT 115, ¶ 3, 327 Mont. 99, 113 P.3d 275. The Montana Supreme Court has clarified that: "Basically, our cases fall into two categories--those that apply a de novo standard of review, thus treating our review of the trial court's decision as a legal question--and those that apply an abuse of discretion standard of review, effectively treating the court's decision as an evidentiary issue." Johnson v. Costco Wholesale, 2007 MT 43, ¶ 15, 336 Mont. 105, 152 P.3d 727. Where an issue presented on appeal does not involve an exercise of discretion by the district court, the appellate court's review of the district court's legal conclusions is de novo, or plenary. See Giambra v. Kelsey, 2007 MT 158, ¶ 26, 338 Mont. 19, 162 P.3d 134. An appellate court reviews discretionary trial court rulings for an abuse of discretion. See Giambra, ¶ 28. When a district court judge is presented with, and resolves, conflicting evidence, the Supreme Court reviews the district court's factual findings to determine whether they are supported by substantial credible evidence and whether they are clearly erroneous. Cole, ¶ 3.
In Montana, there are two levels on which appellate review may occur. A district court has appellate jurisdiction "in cases arising in justices' courts and other courts of limited jurisdiction in their respective districts" (this includes, for instance, decisions of special masters). Section 3-5-303, MCA. The Montana Supreme Court has appellate jurisdiction over "all cases at law and in equity;" that is, it reviews district court decisions when the district court either exercises its original jurisdiction or acts in an appellate capacity. See § 3-2-203, MCA. The level of deference to which a district court's determination on a given issue is entitled may vary depending on whether the district court is acting as the fact-finder.