Just to provide a bit more clarity here, understand that federal taxes are governed by federal laws. The court that awarded you custody is not a federal court. It's a state court or lower. So with that clarified;
Federal law states that for a non-related person to qualify as your dependent, they must have lived in your household the entire year. The only legal entity that can "over ride" that rule in your favor would be a federal judge. Since federal courts do not deal with divorce, separation or custody cases I am 100% confident that will never happen. So regardless of what a lower court says and regardless of what lower level laws (such as state laws) may say, it flat out can not over ride federal law. Period.
But if your state taxes personal income your state laws "may" allow you to claim the dependent on your state tax return. But you flat out can not claim the dependent on your federal return.
