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  • Writer's pictureBen Slater

Understanding Testamentary Capacity: Navigating Law and Mental Health


Understanding testamentary capacity is a topic that involves both legal and psychological considerations. When it comes to estate planning and writing wills, one must have the ability to comprehend and appreciate the claims that are being made, especially when distributing assets after death. In legal parlance, this ability is termed "testamentary capacity."

Natural Faculties and Testamentary Capacity

Testamentary capacity is generally about a person's natural faculties—i.e., the cognitive and emotional abilities to make sensible decisions. Information relevant to the decisions must be understood and assessed appropriately. If there is a mental illness that influences these abilities, then the validity of the will could be questioned. This is why a capacity assessment may sometimes be needed.

Legal Tests for Testamentary Capacity

The primary legal test for determining testamentary capacity dates back to the 19th-century case of Banks v Goodfellow (1870). According to this foundational case law, a person must:

- Understand the nature of the act they are doing

- Understand the extent of the property they are bequeathing

- Comprehend and appreciate any claims to which they ought to give effect

- Have no disorder of the mind or delusions affecting the will

Mental Illness and Testamentary Capacity

If there is a mental illness that influences one’s natural faculties, then the testamentary capacity can be compromised. In such cases, a testamentary capacity report is often recommended. This is a comprehensive evaluation that can either affirm the individual’s capacity at the time of writing the will or indicate issues that might prevent the exercise of such capacity.

The Mental Capacity Act 2005

In the UK, the Mental Capacity Act 2005 serves as a more modern guideline for capacity assessment. This act gives additional layers to understand the mental capacity requirements not just for testamentary decisions but also for other kinds of financial and personal decisions.

Assessing Testamentary Capacity

If you're a legal or healthcare professional assessing testamentary capacity, it is crucial to be aware of both the Banks v Goodfellow test and the Mental Capacity Act 2005 to make a well-informed judgment. If there is any doubt about someone’s ability to understand the nature and implications of their will, please contact experts in the field of mental health and law.

For specialised guidance or assessments, you can contact Nellie Supports at or call them at 0333 987 5118.

Disorder of the Mind and Sense of Right

A disorder of the mind can sometimes be subtle and not readily apparent. It can either influence one's sense of right or prevent them from fully understanding the implications of their decisions. This is why a thorough capacity assessment is essential to ensure the will is both legally and ethically sound.


Understanding testamentary capacity is a complex task requiring a nuanced approach that balances both legal and mental health considerations. With legal standards like the Banks v Goodfellow test and modern guidelines like the Mental Capacity Act 2005, professionals have a strong foundation for assessing capacity.

If you have further questions or need an expert assessment, please visit Nellie Supports at or call 0333 987 5118 for comprehensive assistance.

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