In WA, a child can choose with whom to live when the child becomes a legal adult or when the child is emancipated. The age of majority in WA when the child becomes a legal adult is 18.
If not 18 or older or emancipated, the child of any age can certainly express the child's desire as to where the child wants to live. However, the parents and the court do not have to consider the child's desire. As the child gets older and can offer mature reasons for the child's desire, the court will give more weight to the child's opinion. However, the court is not bound by the child's opinion.
The parent who uses the child to create conflict (such as by encouraging the child to make immature demands) may end up having the parent's parental rights restricted.
Good question, I get this question a lot in my practice.
There is no age at which a child can decide with whom to live.
Courts also discourage declarations and testimony from children, of any age, in contested parenting cases.
In contested parenting cases, a guardian ad litem or a parenting evaluator can be appointed. They investigate the situation and make a recommendation to the court regarding the placement of the child.
If this is a situation where you are considering a modification, it can be a basis for a modification if "The child has been integrated into the family of the petitioner with the consent of the other parent in substantial deviation from the parenting plan".
You could probably get a more detailed answer to your questions if you post a few more facts regarding the circumstances.
the age of majority in WA is 18. After 18, the child is legally an adult and can live whereever he/she chooses.
Before then, the child is supposed to live whereever the parenting plan requires. However, as the child matures and gets older, the court will be more willing to consider the child's expressed wishes.
in king county, the best way to get a child's expressed wishes into evidence is to have him / her talk to a therapist. the therapist would then write a decl. reporting what the child told them and prob. expressing their own opinion about the best resid. sched. for the child.