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Gosh, he did not have his marbles when he made the will - is it valid?

Often, when dealing with estate disputes, we hear family members commenting on the deceased’s mental capacity and querying the validity of the Will made.

In estate disputes, the will-maker or testator’s lack of mental capacity to make a Will may form the basis for challenging the Will. Such cases have increased over the years.

This is unsurprising as dementia is a leading cause of death in Australia. Dementia is a term used to describe a group of conditions that affect the brain’s normal function. These conditions may affect memory, thinking, speech, mobility and personality. Dementia Australia, the peak body representing people who have dementia and their caregivers estimate that in 2020, 459,000 Australians are living with dementia and that without a medical breakthrough, this is expected to increase to 590,000 by 2028 and 1,076,000 by 2058.

The courts have consistently held that in determining whether the testator had the “soundness of mind” to make a Will, the test is whether the testator was sufficiently clear in his or her understanding of the following:-

  • The nature of the document, namely that the testator was making a Will.
  • The nature and extent of the testator’s assets including real estate, cash, superannuation, shares and other investments.
  • The persons the testator was nominating as beneficiaries under the Will and in relation to such nomination, the persons who could make a claim against the testator’s estate if they were left out or were not adequately provided for under the Will and the moral obligations that the testator owed to such persons.

Overall, the testator must have the mental ability to carry out “higher order executive functions” which is the ability to integrate all the above factors and make a plan for the distribution of his or her assets. In making this distribution under the Will, the testator must not have been affected by any mental disorder that influenced his or her affections and judgment.

The burden of proof of testamentary capacity is on the person seeking to uphold the Will made by the testator.

While each case must be assessed in accordance with its own specific set of circumstances, case law has given consideration to the following factors when determining the deceased’s mental capacity:-

  • Whether prior to making the Will, did the testator give any indication of his testamentary intentions, that is the testator’s chosen beneficiaries and the nature of the assets that the testator intended to leave to such beneficiaries.
  • Whether the will made was different to such prior intentions and if so, whether the testator provided any reason for the change in his or her testamentary intentions.
  • Whether there was evidence that the testator suffered from periods of confusion or delusion;
  • While the testator could have some understanding of his or her financial affairs and had periods when the testator was lucid, whether there is medical evidence that the testator did not have the capacity to carry out “higher order executive functions” of the brain when making the Will.
  • Whether the solicitor who had prepared the Will had made a fully informed assessment of the deceased’s testamentary capacity.

Challenging the mental capacity of the deceased in relation to the Will made is not a straightforward task. Evidence from various parties as to the state of the mind of the deceased such as family members, carers and health professionals caring for the deceased, medical practitioners treating the deceased and the solicitor preparing the Will must be obtained and assessed.

If the court finds that the deceased did not have the required mental capacity to make the Will, the court will not grant Probate for that Will.  Instead, Probate may be granted for an earlier Will made at a time when the deceased had mental capacity  If the deceased did not have an earlier Will, then the deceased would be found to have died intestate, that is without a Will. The deceased’s estate will then be distributed in accordance with the law without regard to the deceased’s intentions or wishes.

If you require legal assistance on challenging a Will based on the deceased’s lack of mental capacity when the will was made, contact us at Robertson Hayles Lawyers on (08) 9325 1700 or by email at


The above content is only intended to provide a general overview of the topic discussed. It is not intended to be comprehensive nor does it constitute legal advice. You should seek legal advice specific to your circumstances before acting or relying on any of the above content.