Author and Publication
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
Citation
Key v Key [2010] EWHC 408 (Ch).
Copywright
Copywright © 2026 Nellie Supports Ltd. All rights reserved.
This article is made available for general information, education and professional reference. It may be downloaded, printed and shared for non-commercial purposes, provided that it is reproduced in full, is not altered in any way, and is properly cited as the work of Nellie Supports Ltd. This material must not be edited, adapted, sold, republished, incorporated into commercial products, or used for commercial training, assessment, report-writing or advisory services without prior written permission from Nellie Supports Ltd.
This article does not constitute legal advice, clinical advice or a substitute for a decision-specific professional assessment. Where legislation, government guidance, court forms or external professional materials are referred to, those materials remain subject to their own copyright, licensing and re-use terms.
When a will is disputed after death, testamentary capacity has to be assessed retrospectively: an expert reconstructs the testator's capacity at the date of execution from the evidence that survives. The legal test remains Banks v Goodfellow: understanding the nature and effect of a will, the extent of the estate in broad terms, and the claims of those who might expect to benefit, with no disorder of the mind distorting the disposition. The opinion stands or falls on contemporaneous records: the will file, attendance notes, medical and care records and the pattern of earlier wills. This guide explains how these opinions are built and used in probate disputes.
Assessing capacity at the date the will was made
A retrospective testamentary capacity assessment asks whether the testator satisfied the legal test at the date the will was executed, which may be years before the question arises and after the testator has died. The assessor cannot meet the person, so the opinion is constructed from the surviving record. Done well, it is a rigorous evidential exercise. Done poorly, it is speculation with a professional signature, and probate courts can tell the difference quickly.
The test remains Banks v Goodfellow at the material time
The question is whether, when instructions were given and the will executed, the testator understood the nature and effect of making a will, the broad extent of their property and the claims of those they ought to consider, free of a disorder of the mind poisoning their affections. The material time matters. Evidence of confusion months later, or of a diagnosis made afterwards, bears on the question only insofar as it illuminates the person's likely state at execution, and the opinion should be anchored explicitly to the relevant dates.
The records that carry a retrospective opinion
The weight of a retrospective opinion comes from the records: GP and hospital notes around the material time, cognitive testing where it exists, medication changes, social care records, the drafting solicitor's file and attendance notes, correspondence in the testator's own hand and the will itself, read against its predecessors. The solicitor's file is often decisive, because a detailed attendance note recording the testator's own explanation of their estate and their reasons is contemporaneous evidence of exactly what the test requires.
Where the golden rule was not followed
Where a will is made by an elderly or seriously ill testator, good practice, often called the golden rule, is for capacity to be assessed and recorded at the time. Many disputed wills exist precisely because this did not happen. Its absence does not invalidate the will, and its presence does not conclusively validate one, but the gap it leaves is the space a retrospective assessment must fill, reconstructing from surrounding records what a contemporaneous assessment would have captured directly.
Witness accounts and their limits
Accounts from family, friends, carers and professionals who knew the testator can add texture the records lack: how the person managed daily life, how they spoke about their estate and their family, and how they changed over time. However, recollection is shaped by time and by interest in the outcome, and accounts from those who benefit or lose under the will must be weighed with particular care. A sound retrospective opinion uses witness evidence to supplement the contemporaneous record, as opposed to substituting for it.
Fluctuation, lucid intervals and the date-specific question
Many conditions relevant to testamentary capacity fluctuate, including delirium, the earlier stages of dementia and mental illness. A testator may have lacked capacity in general whilst retaining it on the day, or presented well socially whilst the specific abilities the test requires had gone. The retrospective question is therefore date-specific and decision-specific, and evidence closest in time to the instructions and execution, such as the attendance note of that meeting, ordinarily deserves the greatest weight.
What a retrospective testamentary opinion should contain
The opinion should identify the material dates, the test applied, every source reviewed, the evidence bearing on each limb of Banks v Goodfellow, the analysis connecting any impairment to the abilities the test requires and a conclusion expressed with calibrated confidence. Where the opinion may be used in contested probate proceedings, it should be prepared to CPR Part 35 standards, with the expert's overriding duty to the court, the range of reasonable opinion and the reasoning set out in full.
The honest limits of retrospective evidence
Sometimes the record cannot support a firm conclusion either way, and the most valuable thing an expert can do is say so, explaining what the evidence establishes, what it cannot and why. An opinion that overstates its certainty is dismantled in cross-examination and damages the instructing party's case along with it. Calibrated, transparent conclusions survive scrutiny, and upon that survival the usefulness of the whole exercise depends.
Key takeaway
A retrospective testamentary capacity opinion stands or falls on its anchoring: the right test, applied at the right dates, built from the contemporaneous record and supplemented cautiously by recollection. The strongest opinions show their working on every limb of Banks v Goodfellow and state their confidence honestly, which is exactly what a probate court needs from expert evidence in a disputed will.
Frequently asked questions
Does a diagnosis automatically mean someone lacks capacity?
No. A diagnosis may explain why capacity is in doubt, but it does not answer the legal question. The assessment must still consider the specific decision, the relevant information, the support provided and whether the person can understand, retain, use or weigh that information and communicate a decision.
What evidence is useful for Testamentary Capacity Assessment?
The will file and the drafting solicitor's attendance notes are usually the most important source, followed by GP and hospital records around the execution date, care records, earlier wills showing the pattern of the person's intentions and any capacity assessment completed at the time. In Key v Key the court criticised the failure to obtain proper capacity evidence at execution and set the will aside.
When is a formal assessment for Testamentary Capacity Assessment useful?
A retrospective testamentary opinion is worth commissioning at the pre-action stage of a probate dispute, before costs escalate, because a clear expert view on the strength of the capacity evidence often determines whether a claim or defence should proceed at all.
Related mental capacity assessment pages
These internal links help readers move from this guide to the most relevant Nellie Supports service page, assessment option or legal framework page.
Facing a disputed will?
Nellie Supports completes testamentary capacity assessments across England and Wales, prospective, contemporaneous and retrospective, through a permanent employed team with every report peer reviewed before delivery. Call 0333 987 5118 or visit the testamentary capacity assessment service page.