Author and Publication
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
Citation
Key v Key [2010] EWHC 408 (Ch).
Copywright
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Assessing capacity at a historical date is a reconstruction exercise with a fixed anchor: the date of the decision. The expert maps the person's condition and functioning around that date, the diagnosis and its trajectory, medication changes, recorded episodes of confusion or clarity, and how the person was actually managing decisions at the time, then applies the legal test for the specific decision as it stood on that day. Capacity earlier or later is context, not answer: a person deteriorating over years may well have had capacity at the anchor date. This guide explains the method and what distinguishes rigorous reconstruction from speculation.
The material time is the whole question
Assessing capacity at a historical date means fixing the analysis to the moment the decision was made: the day instructions were given, the date the deed was signed, the period over which a transaction unfolded. Everything else, the diagnosis made later, the decline that followed, the presentation years on, matters only insofar as it illuminates that moment. The commonest failure in historical assessments is drift, where evidence from the wrong period quietly decides a question it cannot answer.
Establishing the timeline before the analysis
The work begins with a dated chronology: when the condition was first noted, when concerns appear in the records, when function changed, and where the decision sits within that course. Building the timeline first disciplines everything after it, because each piece of evidence can then be placed relative to the material date and weighted by its distance from it. An opinion that cannot say where its evidence sits in time is an opinion about the condition, not about the decision.
The trajectory of the condition
Conditions move differently, and the trajectory is itself evidence. A slowly progressive dementia makes function at the material date partially inferable from function documented before and after it. A vascular course moves in steps, so a single event between two records can change everything. Delirium, infection and medication effects produce dips that recover, meaning incapacity documented in one week says little about the week before. The opinion should name the trajectory it relies upon and the evidence for it.
Fluctuation and the possibility of a lucid interval
Where capacity fluctuated, the person may have been able to make the decision at the material moment despite difficulty either side of it, and the law recognises exactly this. Evidence closest to the moment therefore carries the greatest weight: the attendance note of the meeting, the account of the witness who was present, the document in the person's own hand that day. The further the evidence sits from the moment, the more the opinion depends on trajectory, and the report should be honest about which it is relying upon.
Anchoring the functional analysis to the date
The functional question is what this person could understand, retain, use or weigh about this decision on that date. Contemporaneous behaviour answers it best: what the person said and wrote at the time, how they conducted the transaction, what those dealing with them observed, whether their actions display the very abilities in question. A person who negotiated terms, queried figures and corrected a draft was demonstrating use and weigh in the act itself, and the record of it outweighs any later generalisation.
Later evidence: what it can and cannot do
Evidence postdating the decision has legitimate uses and dangerous ones. A diagnosis made afterwards can confirm that an impairment existed earlier, since most conditions do not begin on the day they are named. Later incapacity, though, does not establish earlier incapacity, and reading decline backwards into the material date is hindsight dressed as inference. The report should state expressly how each piece of later evidence is being used and why that use is legitimate.
The presumption of capacity at a distance
The presumption of capacity applies to the historical question exactly as it applies today, and the burden rests on those asserting incapacity at the material date. Where the record is thin, the presumption is not displaced by suspicion, by the size of the transaction or by the fact of a diagnosis alone. An honest historical opinion sometimes concludes that the evidence cannot displace the presumption, and that conclusion is a finding, not a failure.
Reporting a date-specific opinion
The report should state the material dates and why they are the right ones, present the chronology, place every source against it, name the trajectory relied upon, show the functional analysis anchored to contemporaneous behaviour and express the conclusion with confidence calibrated to the evidence's proximity and quality. A reader should be able to see not only what the opinion concludes but how close to the moment its foundations actually reach.
Key takeaway
Capacity at a historical date is decided by the moment, and the method is proximity: build the chronology, weight every source by its distance from the material time, use trajectory honestly and let contemporaneous behaviour speak loudest. Hold the presumption of capacity in place throughout, and the opinion will describe the person as they were, not as hindsight remembers them.
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 Retrospective Mental Capacity Assessment?
Evidence spanning the anchor date from both sides: records shortly before and after are what allow the expert to interpolate the person's likely functioning on the day itself. Single distant snapshots, in either direction, prove little.
When is a formal assessment for Retrospective Mental Capacity Assessment useful?
A formal dated opinion matters wherever the timeline is the battleground: wills executed during a decline, transactions between diagnosis and deputyship, or disputes where each side points to different moments of lucidity or confusion.
Can someone have capacity for one decision but not another?
Yes. Capacity is decision-specific and time-specific. A person may be able to make some decisions independently but still need assessment for whether the person had capacity for a specific decision at a previous point in time, especially where the decision has legal, financial, welfare or court consequences.
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.
Capacity at a specific past date in issue?
Nellie Supports provides retrospective capacity opinions across England and Wales for probate disputes, contested transactions and professional negligence matters, with every report peer reviewed before delivery. Call 0333 987 5118 or visit the retrospective assessment service page.