Legally, intervention refers to the procedural process where a third-party to a lawsuit can interject itself into the suit as a party because it has an interest . Intervention may be permissive or as of right. Both are governed by Missouri Supreme Court Rule 52.12.
Permissive intervention is provided for by Rule 52.12(b) and is available (1) when allowed by statute; (2) when an applicant’s claim or defense and the main action have a question of law or fact in common; or (3) when the State is seeking intervention in a case raising constitutional or statutory challenges. State ex rel. Nixon v. Am. Tobacco Co., 34 S.W.3d 122, 131 (Mo. 2000); Rule 52.12(b).
Intervention as of right is slightly different. To intervene as of right, the applicant must show three things: (1) an interest in the subject matter; (2) a disposition of the action that may impede the ability of the applicant to protect that interest; and (3) the applicant’s interests are not adequately represented by the existing parties. Whitehead v. Lakeside Hosp. Ass’n, 844 S.W.2d 475, 479 (Mo. Ct. App. 1992); Rule 52.12(a). If an applicant meets these requirements, the right to intervene is absolute. Id. at 478-79.
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