What is the test for a judge to determine whether a spouse has a valid claim for custody of their children?

custody and on visitation. (In re Marriage of Burgess (1996) 13 Cal.4th 25, 32, 51 Cal.Rptr.2d 444, 913 P.2d 473.) The trial judge, having heard the evidence, observed the witnesses, their demeanor, attitude, candor or lack of candor, is best qualified to pass upon and determine the factual issues presented by their testimony. (In re Marriage of Lewin (1986) 186 Cal.App.3d 1482, 1492, 231 Cal.Rptr. 433.) An abuse of discretion occurs when the trial court exceeds the bounds of reason; even if we disagree with the trial court's determination, we uphold the determination so long as it is reasonable. (Stull v. Sparrow (2001) 92 Cal.App.4th 860, 864, 112 Cal.Rptr.2d 239.) We do not reverse unless a trial court's determination is arbitrary, capricious, or patently absurd.