Rule 17.Parties Plaintiff and Defendant; Capacity

Rule 17 requires that a civil case be prosecuted in the name of the real party in interest — the person or entity that owns the claim being asserted. The rule then lists who can sue in their own name without joining the person they represent: an executor, administrator, guardian, conservator, trustee of an express trust, someone who contracted on another's behalf, or a party a statute authorizes to sue alone. When a statute allows an action for someone else's benefit, that action is brought in the name of the People of the State of Colorado.

The rule also addresses who can sue on behalf of people who can't easily sue for themselves. A partnership or other unincorporated group can sue or be sued under its own name to enforce a substantive right. Either parent, or the sole surviving parent, can bring an action for the injury or death of a child, and a guardian can bring the same kind of action for a ward.

For children and people found incompetent, a general guardian, conservator, or similar fiduciary can sue or defend on their behalf. If no such representative exists, or the representative won't act, the child or incompetent person can proceed through a next friend or a guardian ad litem, and the court must appoint a guardian ad litem for anyone in that position who isn't otherwise represented — except that no such appointment is needed for an unknown person who might be a minor or incompetent in an action against property itself rather than a person.