Definition - What does Testamentary Capacity mean?
Testamentary capacity means the ability to write a will. Typically, in order to possess testamentary capacity, a person must be at least 18, and must also be sound of mind enough to understand what he or she possesses, and to whom he or she will be giving those possessions to.
Justipedia explains Testamentary Capacity
If a person does not possess testamentary capacity, and he or she attempts to write a will, then this will can be voided. The reason is because without testamentary capacity, the person writing the will may not fully understand what he or she is saying. For example, people with severe Alzheimer's disease or dementia may not comprehend the terms of the will. This could result in someone else manipulating them, or for the will to simply be incoherent or non-functional.