Unravelling the Validity of Wills: Insights on Mental Capacity and Disputes

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Nicola Moulds - Senior Associate


Sometimes, a dispute can arise as to the validity of a will. 

A will can be challenged on one or more of the following grounds:

  1. Lack of proper execution – e.g., not signed or witnessed;
  2. Lack of the necessary mental capacity – discussed below;
  3. Lack of knowledge and approval of the contents of the Will;
  4. Undue influence – that the testator’s mind was so dominated that their decisions were not truly their own; and
  5. That it is a forgery or a fraud.

If the validity of a will is challenged, the courts can ultimately determine whether or not the Will was validly executed. If the court finds that the Will is not valid, its terms do not have any legal effect, and the estate will be administered in accordance with the previous valid Will or the intestacy rules.

This sort of issue can engage emotions, as well as grey matter.

Often, sound legal advice can help translate a mountain of worry into a much more surmountable problem.

To be clear, what follows is not an exhaustive summary of the law or formal legal advice.

But hopefully, it might help the reader to understand the basic issues in an argument over the validity of a will on grounds of mental capacity

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Contesting a will

Testamentary capacity

‘Testamentary capacity’ is the ability of a person making a will to understand the nature and effect of the Will.

If the testator (the person making the Will) lacked testamentary capacity when the Will was signed off, the terms of the will lose their effect.

An old case called Banks v Goodfellow is still good law in relation to the test for testamentary capacity.

It requires that the person making the Will: 

(i) Understands the nature and effects of the act of making the Will;

(ii) Understands the extent of the property which is included in the Will; 

(iii) Understands and appreciates who might (and might not) benefit from their estate;

(iv) Is not suffering from a disorder of the mind such as to poison their affections or prevent the exercise of their natural faculties so that the Will differs from what they would have determined if of sound mind; and

(v) Is able to exercise the decision-making powers required to make the Will (bearing in mind that an adult with impaired mental capacity is capable of making some decisions for themselves, even if assistance is sometimes required).

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Testamentary capacity

How does the court determine the validity of a Will?

Like most issues which come to court, the question of mental capacity is a question of fact. As such, it is rarely a ‘black and white’ issue.

The court will determine it based on evidence, and this usually means that it is difficult to predict the likely outcome with absolute certainty.

If the validity of a will is challenged on the grounds of testamentary capacity, as long as those challenging the will have brought some evidence which casts doubt as to the mental capacity, those who suggest that the Will is valid will be required to prove that the testator had the requisite mental capacity. 

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How does the court determine the validity of a Will

Evidence of mental capacity

Evidence of mental capacity can come from lay witnesses and medical experts.

The usefulness of medical experts can sometimes be limited because they will often be seeking to retrospectively comment on someone’s mental capacity after their death.

Arguably, witness evidence – from people who spent time with the testator – can be much more persuasive.

In particular, real-world examples of what the testator could or could not understand when the Will was executed can often be decisive.

However, there can be competing accounts about the extent of a testator’s comprehension.

If so, the court will be tasked with weighing up the relevant evidence and making a determination on whether or not the deceased had testamentary capacity.

In some cases, there is medical evidence about a testator’s mental capacity from the time when the Will was signed off.

In such cases, the medical evidence can prove to be of substantial value, but much will depend on the expertise of the author of such evidence.

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Evidence of mental capacity

Who can help me challenge the validity of a Will

If you have concerns about the validity of a Will or other testamentary document, give us a call for a free initial chat. 

Unlike most other solicitors’ firms, we have a dedicated team who deals wholly with contentious probate disputes, that is, legal claims about the distribution of the estates of deceased persons. We do not simply dip our toes into this area. We live in it. 

More importantly, we are not just lawyers. We are real people who are well-used to dealing with clients dealing with highly emotive cases. We value competence and compassion in equal measure.

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Nicola Moulds's profile picture

Nicola Moulds

Senior Associate

Nicola has over 14 years of experience acting as a Contentious Probate solicitor. Nicola has specialist expertise in disputes as to the validity of wills, claims against personal representatives, trustees and professionals, applications for the removal of executors, as well as burial disputes.

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