Also known as: sane memories · sound mind · compos mentis
Written by attorneys · grounded in primary & secondary sources — see below
The mental capacity to understand in a general way the nature and extent of one's property, the natural objects of one's bounty, and the disposition being made of that property, together with the ability to relate these elements and form an orderly desire regarding the disposition.
Sylvia Santos, age seventeen, signed a document leaving her violin to a friend. After her death the following year her mother challenged the instrument in probate. The court held the document ineffective because Sylvia lacked the required mental capacity at execution.
Samantha Stone, an aging dairy farmer, executed a typed will leaving equipment to her son. Two adults of sound mind witnessed the signing. After her death other children argued the will was invalid, but the court upheld it because Samantha possessed the mental capacity to understand her property and form an orderly plan.
Sasha Stone signed her will in a company lab. Two lab technicians witnessed the execution. A compliance officer later administered an oath and attached a self-proving affidavit. After her death beneficiaries disputed validity, but the court examined whether the witnesses possessed the necessary mental capacity.
Select any source to read its text and confirm it supports the definition.
Scott Summers, seventeen, signed a letter directing annuity payments to his stepbrother. He died two weeks later. His mother claimed the funds as sole heir. The court ruled the letter void because Scott lacked the mental capacity to understand the nature of his property and form an orderly disposition.
Sydney Santos prepared and signed a document as her will at her desk. She later acknowledged it to two agents in the hallway. The agents signed later that day. After her death a contestant challenged the instrument, requiring the court to assess whether Sydney possessed sound mind at execution.
Sarah Sullivan signed her will in a clinical lab. Two technicians signed as witnesses. A compliance officer administered an oath and attached an affidavit. After her death the beneficiaries disputed self-proved status, prompting inquiry into whether Sullivan had the mental capacity to execute a valid will.
A person must be at least eighteen years old and of sound mind. Both elements are independent statutory prerequisites. Failure of either renders the instrument void regardless of donative intent or formal execution.
Supporting sources
No. Modern probate statutes provide that an interested witness who is otherwise competent may attest a will. The witness's interest does not invalidate the will or any provision in it.
Supporting sources
The rule protects minors from making irrevocable decisions about property disposition. It supplies certainty in probate by establishing a clear threshold that cannot be overcome by evidence of functional independence or apparent maturity.
Supporting sources
…however, the trust company, pursuant to the requirements of § 100-c (9), had notified by mail each person of full age and sound mind whose name and address were then known to it and who was "entitled to share in the income therefrom. . . [or] . . . who would be entitled to share in the principal if the event upon which…