"Juan" makes his will. A year later, he is diagnosed with Alzheimer's disease, and so loses testamentary capacity. Often, the medical diagnosis for Alzheimer's comes well after the victim's judgement becomes impaired.

Based on his later diagnosis, would a court be likely to say that Juan lacked testamentary capacity at the time of the writing?

Note: while tagged and , I am also interested in how this would be interpreted elsewhere.

1 Answer 1


A person must have testamentary capacity to write a valid will. This means that they must have knowledge of the nature and extent of their property, knowledge of the natural objects of their bounty, knowledge of how the will would dispose of the property and the ability to make a rational plan as to the disposition of the property.

A person diagnosed with Alzheimer's today does not thereby lack testamentary capacity, that is a separate question of fact. There is a test which, if taken, could establish lack of testamentary capacity. Without such evidence, gathered at the time the will was made, there would be no legal basis for rejecting the will.

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    But probably, if you find witnesses who state that Juan already was very forgetful and gave strange answers one year before the diagnosis, this might be ground for rendering the will invalid? Commented Nov 29, 2023 at 14:30

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