123 Nev. 145, 161 P.3d 239 (2007)
This case overruled 40 years of case law and established a new child custody standard in Nevada. This standard must be applied to every child custody case involving primary custody in Nevada.
Custody standard; overrules Murphy v. Murphy. The Supreme Court in the case of Ellis v. Carucci, 123 Nev. 145, 161 P.3d 239 (2007), held that a modification of primary physical custody is warranted only when (1) there has been a substantial change in circumstances affecting the welfare of the child, and (2) the modification serves the best interest of the child. The Court in that case found that the decline in the child’s academic performance and other factors while she was with her mother, was a sufficient change to support the modification of custody to joint physical custody.