In civil litigation, defendants often plead affirmative defenses. An affirmative defenses is an additional fact which, if true, defeats a plaintiff’s claim. For example, the statute of limitations is an affirmative defense. A plaintiff may allege, then, that because plaintiff’s claim is untimely the lawsuit fails. The most meritorious claim in the world will be unsuccessful if it is untimely.
In rare circumstances, there can be a defense to an affirmative defense. More specifically, “[a]n avoidance is an affirmative defense to an affirmative defense.” Billings Mut. Ins. Co. v. Cameron Mut. Ins. Co., 229 S.W.3d 138, 143 (Mo. App. S.D. 2007); Rule 55.01. To give an example, if a defendant asserts that a contract is void because he/she was drunk at the time of signing, the opposing party can assert that the contract was ratified. Therefore, to negate an affirmative defense with new facts, an avoidance must be pleaded in a reply If the avoidance is not pleaded, it is waived.