Undue influence is a legal theory which may be used to invalidate a document, usually a will, trust or non-probate transfer. Undue influence occurs when a signer of a document is influenced by “force, coercion, or overpersuasion” such that it destroys the signer’s free agency. Tobias v. Korman, 141 S.W.3d 468, 475 (Mo. Ct. App. 2004). Importantly, even when evidence of influence is shown over a signer, it does not amount to undue influence unless it removed the signer’s free agency. Sleepy Hollow Ranch, LLC v. Robinson, 373 S.W.3d 485, 493 (Mo. Ct. App. 2012).
Undue influence claims greatly depend on the facts. It also greatly depends on the relationship between the influencer and the individual subject to the undue influence. For instance, it is much more difficult legally to prove undue influence between spouses because marriage is an inherently close relationship. It is “the rule that a husband or wife may justly and properly influence the making of a will or deed by the other for his or her own benefit, so long as the influence is not exercised in improper manner or by improper means.” Snell v. Seek, 250 S.W.2d 336, 342 (Mo. 1952).