Annulment is the nullification of marriage, and most states allow it only on very narrow grounds. One such ground is mental incapacity at the time of marriage. The law expects that the parties entering the marriage contract should be able to understand the nature and consequences of marriage.
Mental incapacity can be described as the absence of the capacity to make decisions for oneself or the ability to express such decisions. As such, mental incapacity may be due to mental illness, stroke, Alzheimer’s disease, congenital disability, and brain injury, among other causes.
Under the law, a marriage is voidable in cases where either of the spouses is incapable of understanding the contract of marriage. Some states hold that if the party is incapable of understanding because of insanity or serious mental disorder, the marriage is void. Some state statutes provide that mental illness can be a ground for annulment if the defect prevents the afflicted spouse from appreciating the contract and conferring thoughtful consent to the marriage. Mere mental weakness alone cannot be a ground for annulment in some states. Moreover, mere variation from normal human behavior or human thinking is insufficient to justify adjudging a person as mentally ill.
In the case of a ward who has been declared mentally incapable before the marriage, the ward’s guardian can give consent on behalf of the ward for the marriage. Without such guardian consent, the ward’s marriage becomes void or voidable. Such a marriage can be annulled because it was without the consent of the guardian, and the ward was incapable of consenting to the marriage. In that situation, the guardian can bring an action to annul the marriage on behalf of the ward. A mentally ill person can enter a valid marriage if he or she is capable of understanding the nature and expectations of marriage. The ability to understand the duties and the responsibilities associated with marriage is the key factor for evaluating mental capacity to enter into marriage.
The foremost evidence to prove a spouse’s mental incapacity is adjudication of mental incapacity by an appropriate authority. That usually involves expert testimony by a psychologist or psychiatrist. A marriage with a person who is mentally incapable usually is valid and legally binding unless and until a court annuls it.