It is common to amend pleadings. The purpose of pleadings are to define the factual and legal issues that are being tried. Generally, judgments which exceed the scope of the claims in a lawsuit and pleadings are improper. Sometimes pleadings may be amended to conform to the evidence presented at trial.
Rule 55.33(b) allows the amendment of pleadings to conform to the evidence when issues not raised in the pleadings are tried by the express or implied consent of the parties. Heritage Roofing, LLC v. Fischer, 164 S.W.3d 128, 132 (Mo. Ct. App. 2005). Express consent is obviously easy to define. Implied consent is more elusive. “The implied consent rule only applies when the evidence introduced at trial bears on a new issue and is not pertinent to issues already in the case.” Id. In other words, the evidence in question should only relate to the non-pleaded matter. The rule has some nuance depending on the situation. For example, “consent to the trial of non-pleaded affirmative defenses should not be implied unless it clearly appears that plaintiff tacitly agreed to join [to] such defense.”Detling v. Edelbrock, 671 S.W.2d 265, 271 (Mo. 1984)