When families start asking whether a will or trust was signed during a period of confusion, dementia, or serious cognitive decline, the conversation often turns emotional fast. People remember unusual behavior, troubling medical episodes, or a sudden estate change that felt out of character. That can be the beginning of a legitimate capacity dispute. It can also become a credibility problem if the case is built the wrong way.
In probate litigation, credibility matters almost as much as the underlying facts. Judges often look at timelines, medical records, witness testimony, drafting-attorney files, and the decedent’s behavior close to the signing date. A capacity challenge that feels organized, grounded, and evidence-based tends to be taken more seriously than one driven by suspicion alone. In general terms, testamentary capacity focuses on whether the person understood the nature of their property, the people who would naturally receive it, the disposition being made, and how those pieces fit together into a coherent plan, as summarized by Cornell Law School’s Legal Information Institute in its overview of testamentary capacity.
This issue is increasingly relevant. The Alzheimer’s Association estimated that 7.2 million Americans age 65 and older were living with Alzheimer’s dementia in 2025, and the CDC continues to track subjective cognitive decline as an important public-health indicator because changes in memory and decision-making can affect day-to-day functioning and long-term planning, including legal and financial decisions. See the Alzheimer’s Association’s 2025 Facts and Figures executive summary and the CDC’s BRFSS cognitive decline overview.
If you are still getting grounded in the basics, it may help to start with a broader explanation of how lack of capacity claims are usually framed in estate disputes. In this post, you’ll learn the seven mistakes that often weaken a capacity contest before the court ever reaches the heart of the dispute.
<aside> 💡 Scroll to the bottom for every post in this series.
</aside>
One of the fastest ways to lose credibility is to assume that a diagnosis ends the inquiry.
A person can have dementia, Alzheimer’s disease, delirium episodes, or another cognitive impairment and still possess the legal capacity to execute a will at a particular moment. That point comes up repeatedly in probate law and commentary. Cornell’s definition of testamentary capacity centers on what the person understood at the time of execution, not whether a diagnosis existed in the abstract. The American Bar Association has also emphasized that legal capacity is task-specific and can differ depending on the document or decision involved, as discussed in its materials on capacity and undue influence involving vulnerable adults.
Recent case reporting from the ABA illustrates the same principle in practice. In Estate of Spofford in Maine, the court reportedly upheld summary judgment against a lack-of-capacity challenge even though the testator had dementia and Alzheimer’s diagnoses, because the record contained substantial evidence of capacity on the day the will was executed, including attorney-recorded videos and physician testimony. See the ABA’s Keeping Current—Probate.
That does not mean a diagnosis is irrelevant. It often matters a great deal. But a diagnosis is usually the beginning of the analysis, not the conclusion. A more credible approach often asks narrower questions: