In complex situations, it is not uncommon for multiple lawsuits to be pending in multiple jurisdictions. When this occurs, one court, in the interests of comity, may allow the other court to handle the entire dispute. At the state level in Missouri, comity is not an ironclad rule, but a rule of “practice, convenience, and expediency.” Ramsden v. State of Ill., 695 S.W.2d 457, 459 (Mo. 1985). “It does not of its own force compel a particular course of action.” Id. Instead, it is an expression of one state’s “entirely voluntary decision to defer to the policy of another.” Id.
Federal case law is similar. Comity comes up when “two identical actions are filed in courts of concurrent jurisdiction, the court which first acquired jurisdiction should try the lawsuit and no purpose would be served by proceeding with a second action.” Koch Engineering Co., Inc. v. Monsanto Co., 621 F. Supp. 1204, 1207 (E.D. Mo. 1985) It is a prudential doctrine of abstention. Midlands States Bank v. Ygrene Energy Fund Inc., 564 F. Supp. 3d 805, 813 (E.D. Mo. 2021).