Testamentary capacity is the legal and mental ability of a person making a will (the testator) to make a legally binding disposition of their assets and to understand the nature and effect of the act of making a will—including disposing of their assets at death.

Proof of testamentary capacity is a required element of a will being admitted to probate and recognized by the court as having legal effect.

Adults are generally presumed to have the legal capacity to make a will, but minors (persons under a certain age) are not—with some exceptions in some states, such as if the minor has served in the military or has been married.

Persons who suffer from dementia, Alzheimer’s disease, or insanity, for example, may lack testamentary capacity to make a will.

In legal jargon, the historical terms of art for testamentary capacity were that the testator was “of sound mind and memory” or “of sound mind and disposing memory,” and this terminology is sometimes recited in a will as a statement of the testator regarding the testator’s mental capacity when making the will.

Laws vary from state to state and the requirements related to testamentary capacity are often located in a state’s statutes—usually in the estates code or probate code—and interpreted and applied by the courts in specific factual circumstances or cases that are reported in court opinions involving will contests, for example.

In Wyoming, testamentary capacity is the legal and mental ability of an individual (the testator) to create a will that lawfully distributes their assets upon death. This capacity includes understanding the nature of making a will and the consequences of distributing their assets posthumously. Adults are typically presumed to have the necessary legal capacity to execute a will, while minors generally do not, except under certain conditions such as military service or marriage. Individuals with cognitive impairments, such as those with dementia or Alzheimer's disease, may be deemed to lack the requisite testamentary capacity. The traditional legal terms 'of sound mind and memory' or 'of sound mind and disposing memory' are historical phrases that may be included in a will to assert the testator's mental capacity at the time of making the will. Wyoming's statutes concerning testamentary capacity are found in the state's probate code, and the courts interpret and apply these laws in the context of specific cases, including will contests. It is important for a will to be recognized by the court for probate, and proving testamentary capacity is a critical element of this process.