Under the law of the case, a motion to modify support can’t be used to relitigate issues already decided by the court in a previous stage of the case. The district court granted the father’s motion to modify child support. The mother did not appeal this order. Almost immediately, the mother filed a new motion to modify. The district court denied her motion based on res judicata and she appealed. The appellate court upheld the denial of the motion. Under the law of case doctrine, which can be raised on a court’s own initiative, the mother couldn’t relitigate an issue decided in a previous stage of the case. The mother failed appealed the first modification order. She couldn’t use a new motion to modify to make the same arguments. The mother also argued the district court  improperly applied the multiple-family standard to calculate support and that this was a material change in circumstances. The appellate court disagreed. No authority supported this argument. And, this situation existed at the time of the earlier modification order, which the mother failed to appeal.