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When someone makes a will, one of the most important questions is whether they had the mental capacity to make that decision at the time.
When someone makes a will, one of the most important questions is whether they had the mental capacity to make that decision at the time.
In England and Wales, Banks v Goodfellow (1870) remains the foundation for a person’s testamentary capacity assessments. In summary, the person must understand the nature and effect of making a will, the extent of the property being disposed of and the claims of those they ought to consider. A disorder of mind or delusion must not influence the disposition in the way described by the test. This common-law framework is distinct from simply applying the MCA functional test.
But while the legal test has remained largely unchanged, the science behind mental capacity assessments continues to develop.
The review by Voskou, Douzenis, Ekonomou and Papageorgiou (2026), published in the Journal of Dementia and Alzheimer’s Disease and cited below, discusses the Testamentary Capacity Assessment Tool (TCAT) and subsequent studies. It is research about an assessment aid, rather than a new legal test for England and Wales.
One of the most common misunderstandings about testamentary capacity is that it is simply about memory.
In reality, making a will is a complex decision. A person may remember their family members and know what assets they own, but still struggle with judgement, reasoning or understanding the consequences of their choices.
The researchers behind the TCAT argue that a thorough testamentary capacity assessment should consider several important abilities, including:
The ability to reason through situations involving trust and influence.
These themes support a useful professional question: what evidence explains this person’s ability to make this will? They do not make a research score a legal threshold for capacity.
One of the most interesting aspects of the research is its focus on structured assessment.
The TCAT uses structured questions and scenarios to explore abilities relevant to testamentary decisions. Before adopting it in practice, an assessor must consider the version, language, population studied and fit with the applicable law. Evidence of utility in one population does not automatically validate a tool for every English or Welsh will-making instruction.
This approach is important because courts often need to understand not only what a person decided, but how they reached that decision.
A well-structured assessment helps ensure that important areas are explored consistently and that conclusions can be clearly explained if they are later challenged. This is one reason why choosing a suitably experienced mental capacity assessor can be so important in complex or disputed will-making situations.
Another important message from the research is that a diagnosis of dementia does not automatically mean a person lacks testamentary capacity.
Many people with mild cognitive impairment or early-stage dementia continue to understand their wishes, relationships and financial circumstances well enough to make a valid will.
Equally, some people may have difficulties with judgement or decision-making that require closer examination.
This is why good assessments focus on the person's abilities rather than their diagnosis alone.
The question is not whether someone has dementia.
The question is whether they can make the specific decision that is being assessed.
At Nellie Supports, we believe that professional opinions should be supported by evidence.
An assessment tool may organise evidence, but it cannot itself decide whether the Banks v Goodfellow requirements are met. Professional judgement still needs to connect the individual evidence with the applicable legal question and explain the tool’s limitations.
Instead, tools and structured interviews help assessors gather evidence, identify relevant strengths and difficulties, and explain how they arrived at their conclusions.
This is particularly important in situations where family members disagree, concerns have been raised about undue influence, or a will may later be challenged. In higher-risk or contested cases, a more detailed Enhanced Capacity Assessment Service may be appropriate where wider evidential work is needed.
The practical lesson I take from this research is the value of structure and transparent reasoning. It does not establish a new testamentary capacity test or prove that using this tool will make a disputed will valid.
For practitioners, useful features to seek are:
These are principles that benefit everyone involved, including the person making the will, their family, legal professionals and ultimately the courts.
Where someone cannot make or change their own will, a statutory will assessment package may help gather evidence for a possible Court of Protection application. The court decides whether to authorise a statutory will; a report or package does not create that authority.
Research in this area continues to develop, particularly in understanding how memory, judgement, social understanding and vulnerability to influence affect will-making decisions.
Research can inform practice, but claims of improved reliability need to be assessed against the study design, validation population and legal context. This review is a reason to examine those methods, rather than assume that every tool or structured interview has the same evidential strength.
At Nellie Supports, we welcome developments that strengthen evidence-led practice and improve the quality of assessments. The goal is not simply to reach a conclusion, but to ensure that conclusions are supported by clear evidence, sound reasoning and a process that can withstand scrutiny.
Because when important decisions about a person's wishes and legacy are involved, the quality of the assessment matters.
You can also explore our wider mental capacity assessment guides for further information about decision-specific capacity.
Voskou, P., Douzenis, A., Ekonomou, A., & Papageorgiou, S. G. (2026). State-of-the-art Testamentary Capacity Assessment Tool (TCAT) in dementia: A review of studies and update report. Journal of Dementia and Alzheimer’s Disease, 3, 25. https://doi.org/10.3390/jdad3020025
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Mental Capacity Act Code of Practice
Published 22 June 2026
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