We review findings of fact under the clearly erroneous standard pursuant to M. R. Civ. P. 52(a). We use a three-part test to determine if a finding is clearly erroneous. First, we examine the record to determine if the findings are supported by substantial evidence. Second, we consider whether the trial court has misapprehended the effect of the evidence. Third, if both of these tests are satisfied, we may still conclude that a finding is clearly erroneous when, although there is evidence to support it, a review of the record leaves the Court with the definite and firm conviction that a mistake has been committed. Kafka v. Mont. Dept. of Fish, Wildlife & Parks, 2008 MT 460, ¶ 28, 348 Mont. 80, 201 P.3d 8 (citing Interstate Prod. Credit Assn. v. DeSaye, 250 Mont. 320, 323, 820 P.2d 1285, 1287 (1991)).
Substantial evidence is evidence that a reasonable mind might accept as adequate to support a conclusion; it consists of more than a mere scintilla of evidence but may be less than a preponderance. Strom v. Logan, 2001 MT 30, ¶ 23, 304 Mont. 176, 18 P.3d 1024.
We view evidence in the light most favorable to the prevailing party, and we leave the credibility of witnesses and the weight assigned to their testimony for the determination of the trial court. Willis v. Fertterer, 2013 MT 282, ¶ 25, 372 Mont. 108, 310 P.3d 544.
"To clarify, our viewing the evidence 'in a light most favorable to the prevailing party' is a subset of the first prong of the three prong standard by which we review a finding of fact asserted to be clearly erroneous, that is, whether the finding is supported by substantial evidence. For purposes of that inquiry, we view the evidence in a light most favorable to the prevailing party. The following correct statement of the complete standards of review recently provided may facilitate clarification of the standards for involuntary commitment cases: We review the findings of a district court sitting without a jury to determine if the court's findings were clearly erroneous. See M. R. Civ. P. 52(a). A district court's findings are clearly erroneous if substantial credible evidence does not support them, if the district court has misapprehended the effect of the evidence or if a review of the record leaves this Court with the definite and firm conviction that a mistake has been committed. Ray v. Nansel, 2002 MT 191, ¶ 19, 311 Mont. 135, ¶ 19, 53 P.3d 870, ¶ 19. Additionally, we must view the evidence in the light most favorable to the prevailing party when determining whether substantial credible evidence supports the district court's findings. Ray, ¶ 19. We review a district court's conclusions of law to determine whether those conclusions are correct. In re Estate of Harms, 2006 MT 320, ¶ 12, 335 Mont. 66, ¶ 12, 149 P.3d 557, ¶ 12; Byrum v. Andren, 2007 MT 107, ¶ 14, 337 Mont. 167, ¶ 14, 159 P.3d 1062, ¶ 14."
In re Mental Health of A.S.B., 2008 MT 82, ¶ 17, 342 Mont. 169, 180 P.3d 625