The most complete list of affirmative defenses available in one place: currently 230 separate affirmative defenses. This is part of Vail Law's Litigation Checklist . Connect with me on LinkedIn .
F.R.C.P. 8(c) requires a party to "set forth affirmatively . . . [any] matter constituting an avoidance or affirmative defense." Consider each of the below affirmative defenses--does it potentially apply in your case? Rule 8(c) requires that both defenses to liability and defenses that potentially mitigate damages must be set forth in the pleadings. Indus. Comm'n v. Ewing , 418 P.2d 296 (Colo. 1966). If a defense is not raised by the pleadings, it may still be tried by the express or implied consent of the parties. See Great Am. Ins. Co. v. Ferndale Dev. Co ., 523 P.2d 979 (Colo. 1974). However, it is error for a trial court to permit a defense over an objection when first presented at trial. Maxey v. Jefferson County Sch. Dist. No. R-1 , 408 P.2d 970 (Colo. 1965). Accordingly, while pleadings may be amended to add additional affirmative defenses, it is essential that all defenses to be raised at trial are pleaded before trial (ideally, at least a week prior to the deadline to serve written discovery in a case).
Note that, unlike affirmative defenses where the defendant bears the burden of proving the defense, some of the following are more properly styled "additional defenses" where the plaintiff bears the burden of proving that the defense does not apply (e.g. service of process). Regardless of how they are styled, the vast majority of these defenses will not apply in any given case, review of the complete list may be an especially helpful tool in brainstorming at the outset of a case. As the vast majority of these affirmative defenses will not apply to any given case, ensure you don't just plead this entire laundry list - this list is intended as a brainstorming tool . Rule 11 requires that you have a good faith basis for believing an affirmative defense actually applies before pleading it, and in discovery you will likely need to respond to an interrogatory identifying all factual bases for every affirmative defense you plead. Additionally, where the factual allegations necessary to plead an affirmative defense are not set forth, the defense may be dismissed pursuant to Rule 12(b), which is normally styled as a "motion to strike."
Enough with the fanfare, here's the (necessarily incomplete) list: