GUIDES
A historical capacity opinion asks whether the person could make a particular decision at the relevant past date. It reconstructs that position from records and witness evidence, using the legal test for that decision and stating what the evidence cannot establish.
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
Key v Key [2010] EWHC 408 (Ch).
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A historical capacity opinion asks whether the person could make a particular decision at the relevant past date. It reconstructs that position from records and witness evidence, using the legal test for that decision and stating what the evidence cannot establish. This guide covers the relevant evidence, support, process and limits in England and Wales.
A historical capacity opinion asks whether the person could make a particular decision at the relevant past date. It reconstructs that position from records and witness evidence, using the legal test for that decision and stating what the evidence cannot establish. Evidence of functioning before or after the date can help, but later decline does not prove earlier incapacity. The opinion should explain the person’s condition, the reliability of each source and any justified inference.
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.
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.
Conditions can follow different courses. Progressive decline, changes after a vascular event, acute illness and medication effects may each affect what can reasonably be inferred about the material date. The expert should explain the course supported by this person’s records, rather than assume a typical trajectory proves their abilities.
Where abilities fluctuated, focus on evidence about the actual decision and the possibility of a better period. A contemporaneous attendance note or witness account can be valuable, but proximity alone does not guarantee reliability. Explain what each source records, what it leaves unanswered and how it relates to the applicable legal test.
For an MCA decision, consider the person’s ability to understand, retain, use or weigh relevant information and communicate at the material time, with any inability linked to an impairment or disturbance. Their words and actions may provide useful evidence without conclusively establishing every ability. For a will, apply Banks v Goodfellow instead of substituting the MCA test.
Later evidence may help establish when an impairment began or how it developed. A later diagnosis does not necessarily show that the condition existed at the earlier date, and later incapacity does not prove earlier incapacity. State the evidence supporting each backward inference and any competing explanation.
For an MCA question, capacity is presumed and lack of capacity must be established on the balance of probabilities. Do not infer incapacity from diagnosis or a large transaction alone. Probate disputes have specific rules about proof of testamentary capacity, so the solicitor should identify the applicable burden rather than assume that the MCA position applies unchanged.
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.
Fix the decision and material date, apply the correct legal test and assess the quality as well as the timing of the evidence. State where the record supports a conclusion and where the past position remains uncertain.
No. A diagnosis does not establish lack of capacity. For a decision under the Mental Capacity Act, consider the relevant information and practicable support, then assess understanding, retention, use or weighing and communication by any means. Any inability must be caused by an impairment of, or disturbance in the functioning of, the mind or brain. Will-making has its own legal test.
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.
A retrospective opinion may assist a dispute about a will, LPA or transaction where capacity at a past date matters. First define the decision and legal test, then consider whether the surviving evidence can answer it. A present diagnosis alone cannot settle the past question.
The related guides below provide further explanation of the decisions, evidence and legal processes discussed here.
Identify the decision and material dates before collecting records. Ask the solicitor handling any dispute which legal test and procedural rules apply, and ask the expert to identify gaps and alternative explanations rather than promise certainty.
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