For a will to be valid, the testator must have sufficient mental capacity. Kerry Morgan-Gould considers how this may be tested.

Testamentary capacity is the legal term used to describe a person's legal and mental ability to make or alter a valid will.

If the person making the will (testator) lacks testamentary capacity at the time that the will is executed, the will is invalid.

The test for capacity to execute a valid will is based in case law. A testator must:

• Understand the nature of making a will and its effects.
• Understand the extent of the property of which they are disposing.
• Be able to comprehend and appreciate the claims to which they ought to give effect.
• Have no disorder of the mind that perverts their sense of right or prevents the exercise of their natural faculties in disposing of their property by will.

The level of understanding required by the test varies according to the complexity of the will itself, the testator's assets and the claims on the testator (Banks v Goodfellow (1870) LR 5 QB 549).

Following the introduction of the Mental Capacity Act 2005 (Gazette issue 57613), which came into force on 1 October 2007, there was initially some doubt as to whether the common-law test provided for in Banks v Goodfellow was superseded by the statutory test set out in the 2005 Act.

The code of practice appended to the Mental Capacity Act is ambiguous on the point, stating that its own definition of capacity is ‘in line with the existing common law tests and does not replace them’, but allowing judges in such cases to adopt the new definition 'if they think it is appropriate'.

The main fundamental differences between case law and the Mental Capacity Act are as follows:

• The Mental Capacity Act test assumes capacity unless proved otherwise. The case law only requires the challenge to raise a 'real doubt', at which point the burden of proof switches to those who claim the testator had capacity.
• The Mental Capacity Act asserts that the testator must be able to understand all the information relevant to the decision, including the reasonably foreseeable consequences. Case law only requires the testator to appreciate the claims to which they ought to give effect in the will, and that the will reflects them. For example, in the Court of Appeal case of Simon v Byford (2014), it was held that inability to understand the collateral consequences of a will does not affect the validity of a will at common law.

Arguably, the Mental Capacity Act is a more stringent test.

Matters were finally clarified in Walker v Badmin (2015), whereby the court stated that 'the correct and only test' for testamentary capacity is the one outlined in Banks v Goodfellow. The court determined that the wording of the Mental Capacity Act suggests it was only ever intended to enable the court to make decisions for living, incapable persons, and not deceased testators. 

Moreover, the threshold for testamentary capacity has traditionally been kept low so as to allow older people to make a will in their declining years, and it was unlikely that parliament would have reversed this policy without announcing the fact. Thus it was concluded that the Mental Capacity Act does not override or modify existing case law, and Banks v Goodfellow and its successors remain in effect.

So when assessing capacity to make a will, practitioners should remember that the modern practical approach to the case law, to consider the testator's potential to understand and make decisions, does not focus exclusively on their actual understanding. Moreover, bear in mind that it is not a memory test; testators can have a poor memory, yet still have capacity. 

Finally, the testator may be capable of assessing the information and understanding it, but can choose not to do so and still have capacity.

About the author

Kerry Morgan-Gould is legal director at Ashfords LLP, @Ashfords_Law.

See also: What are statutory wills, and when are they necessary?