For any will to be legally binding, its author must have (or be deemed to have had) the ability to understand the nature and effect of their will at the time of it’s writing. The capacity to understand the nature and effect of a will at the time of writing is referred to as ‘Testamentary Capacity’.

The same applies where an individual is looking to amend an existing will. He or she must be deemed to have testamentary capacity in order to make such changes in a legally binding manner.

Testamentary capacity is therefore determined by an individual’s ability to understand the nature and the effect of their will at the time that the will is made.  In the vast majority of cases where the integrity of brain function is not in question, there is no need for an individual to undergo formal assessment of their testamentary capacity.  However, where further evaluation is required in order to establish testamentary capacity, Clinical Neuropsychologists are arguably best placed of all clinicians to perform this type of evaluation and to provide expert opinion.

Having a diagnosis of dementia or any other condition affecting your thinking ability does not automatically negate your ability to write a legally binding will.  The testamentary capacity of an individual with dementia will depend on a number of matters including:

• How long they have suffered with dementia.
• The severity of their cognitive losses.
• The type of thinking difficulties they experience (i.e. whether these relate to memory or language function).
• The level of complexity of their estate.

In some cases, it may be possible to facilitate the testamentary capacity of an individual via the adoption of strategies to support their function in the affected area of thinking.

Some people get help from friends or family or simply write their will themselves.  The advantage of seeking professional advice is that a proper capacity assessment can be undertaken at or close to the time that the will is written, forming a safeguard against any future challenges on grounds of incapacity.

Where wills are challenged on grounds of an absence of testamentary capacity, Clinical Neuropsychologists may be called upon to provide an expert opinion on a retrospective basis.  In such cases, Clinical Neuropsychologists integrate specialist knowledge of the symptoms and course of brain diseases with details / circumstances of their client, to infer the likelihood of testamentary capacity at the time the will was written.