Giles Eyre considers a recent case in which an expert was criticised for changing their opinion and provides tips for experts on how to avoid too many unfortunate consequences.

An expert must avoid changing their opinions, but a recent case is a reminder that there are circumstances when it is the right thing to do. Giles Eyre, considering a recent case, takes the reader through this minefield and provides tips on how to avoid too many unfortunate consequences.


In the course of training as an expert witness, a common exhortation is not to change opinions. The expert who is seen to ‘wobble’ is unlikely to carry the confidence of the court and will likely be exposed to aggressive cross-examination. If the case is being considered prior to trial, a communicated inconsistency in the expert’s opinion is likely to weaken the negotiating position of the party relying on that expert. Therefore, the expert should come carefully to a considered and justifiable opinion, and stick with it.


But it isn’t necessarily that simple. In a recent family law case, an expert witness was criticised for changing their opinion in the course of the case. A Local Authority v AA & Anor [2022] EWHC 2321 (Fam) was concerned with whether a child had suffered an intentional shaking injury at the hands of a parent, or whether the injuries were consistent with a low-level fall. The judge concluded that, in what was clearly a highly contentious field, the criticised expert had “done what any expert should do.”

The judge continued: “She kept an open mind and conducted as thorough a review as possible of the literature before reaching her ultimate conclusion.”

Indeed, in exercising their duty to the court to assist the court on matters within their expertise, experts must keep an open mind. Therefore, it is wholly appropriate if they have a change of view after reviewing the matter. 

When it is acceptable for an expert to change an opinion

‘If at any time the expert can no longer support the case of the person who instructed him, it is his duty to say so. Indeed, if the expert forms that view it is far better that he says so sooner rather than later before the litigation costs escalate.’ Guntripp v Cheney Coaches Ltd [2012] EWCA Civ 392

Such a change of opinion may be for a number of reasons. It may be as the result of:

  1. Further information coming to light, such as following disclosure of further medical records, or following production of a further statement from the claimant or a witness statement, or in surveillance film
  2. A subsequent examination of the claimant resulting in different findings
  3. The expert’s consideration of matters raised in the report of another expert in the case, and which had not previously been considered by the expert or given sufficient weight, for example, a different explanation for a finding or set of facts
  4. Flaws in the initial report being pointed out by the opposing expert or lawyers, such as a misreading of a record or an error in a date or time
  5. The expert, on reflection, changing their mind.

The first two reasons – further information and subsequent examination – are perfectly understandable and excusable. The expert, in explaining the reason for the change of opinion, should not lose credibility. However, the other three reasons reflect unfortunately on the expert. Obviously, if they do arise, then the change in opinion must be communicated, but the instructing party is entitled to feel aggrieved – although perhaps less aggrieved the earlier in the litigation this occurs.

The expert might naively believe that what is important is the truth, and therefore changing opinion to a more cogent one can only be a ‘good thing’. But litigation is not only combative and adversarial, it is also expensive. For a legal team that has invested time and, therefore, money in a claim, many thousands of pounds could well be lost when the expert changes an opinion and the party’s position in the litigation is undermined. For the party, suddenly finding that a good case is no longer sustainable is extremely disappointing.

Avoiding pitfalls

The likelihood of this situation where an expert changes their opinion arising is increased by the constraints of litigation. 

In many lower value claims the expert is required, under the Civil Procedure Rules and the pre-action protocols, to provide a report in the absence of medical records, or with only a small selection of medical records. The instructing lawyer is also working under constraints which impact on the time they wish to spend on the case (and for which they will be paid), and this may well feed into the amount of documentation that it is desired to be provided to the expert. Providing an opinion (and the whole report) in this situation requires the use of a number of skills by the expert. 

Firstly, the expert must be sure to state within the report what, if any, records have been seen, so that, if other documents subsequently arise which throw a different light on matters, the ground for that change of opinion has effectively been set. In low value claims, the relevant records which are seen will be attached to the report.

Secondly, in the absence of the provision of complete medical records, the expert must make sensible inquiries of the claimant and record the responses within the report, so that the factual matrix upon which the opinion is based, is clear. Questions of a claimant must be clear and unambiguous in nature and framed in a form and in words that are appropriate for the particular claimant. The answers must be clearly understood, and all ambiguities removed.

Therefore, if reporting on a soft tissue injury in the absence of medical records (or most of them), the expert makes that situation clear in the report, and asks, for example, whether the claimant has suffered relevant aches and pains or restrictions of activities prior to the index event, and records the response within the report.  There is then no difficulty in terms of the credibility of the expert, on seeing records describing a relevant history which was not described at all or adequately in answer to questioning, in changing the opinion as appropriate.

Procedure on changing opinion

Assuming the change of opinion occurs before the trial itself, if the expert changes their mind, two actions are required:

  1. The change of opinion must be communicated to the lawyers and the partied without delay
  2. The change of opinion must be explained to the instructing lawyers and party, as they are entitled to understand the process that has resulted in the change of opinion, particularly if the change is to the detriment of that side’s case. Even at trial, immediate communication of the change of opinion, together with a thorough explanation of the reason for it, is required.

If a change of opinion were to result in an opinion that is more favourable to the instructing party and so is to the detriment of the other side’s case, then it is important to set out the reasoning in order to explain fully why the change of opinion is justified. Otherwise, the apparent inconsistency could again cause the expert to lose credibility before the court and the revised opinion may not be given due weight.

The procedure to follow in such circumstances is set out in the guidance:

Guidance 66: Where experts significantly alter their opinion, as a result of new evidence or for any other reason, they must inform those who instruct them and amend their reports explaining the reasons. Those instructing experts should inform other parties as soon as possible of any change of opinion.

A change of opinion, and this includes a change of opinion within a report where the expert continues to support the case of the party by which they are instructed, must be communicated to the instructing lawyer without delay (guidance para 14). The client is also entitled to know, as soon as is practicable, the basis for a change that may have disastrous and expensive consequences on the litigation. In failing to communicate the reasons clearly and immediately, the expert is likely to complicate what is almost certainly in any event a difficult situation.

Where a change of opinion occurs at a discussion between experts, the guidance suggests a slightly different approach:

Guidance 66: Where experts change their opinion following a meeting of experts, a simple signed and dated note to that effect is generally sufficient.

However, there may be circumstances where the change of opinion is such that it is more appropriate to amend the report to reflect the changes of opinion, and to provide the reasons for the changes. Generally, experts should not simply sign a document recording their change of opinion after a meeting of experts, but as more generally with any change of opinion (and for the same reasons) should give reasons for the change. If it is necessary to give a detailed explanation for the change of opinion, then it will be best to follow the suggested alternative of an amended report offering full reasons for the change of opinion. Particularly at this late stage in the litigation, the instructing party is entitled to know why the expert has had a change of mind and is no longer willing to be supportive of the client’s case.

Learning points

  1. An expert should produce a reliable and justifiable opinion so that a subsequent change of opinion is not necessary.
  2. In most circumstances, a change of opinion will reduce the expert’s credibility.
  3. A change of opinion must be justified and explained, and the instructing solicitor informed as soon as is possible.
  4. If the justification and explanation does not reflect on the care with which the expert’s original opinion was reached, then the expert’s credibility should not be affected.
  5. The expert must be clear about the factual matrix on which the original opinion is based and as to any reservations that might be applied to that factual matrix.

Giles Eyre is a retired barrister and an Associate Member of Deka Chambers, London, having practised for many years in the field of injury claims and at the interface of law and medicine. He continues giving training and presenting workshops for experts on providing effective expert reports and evidence, and on medico-legal issues, in his own right and for training organisations. He is co-author of Writing Medico-Legal Reports in Civil Claims – an essential guide (2nd edition 2015), and author of Clinical Practice and the Law – a legal primer (October 2018) both published and sold by Professional Solutions Publishing ( and through book retailers, and regularly writes articles on these subjects.  He blogs on issues relevant to court experts in civil claims at .

Special Offer: ‘Clinical Practice and the Law – a legal primer’ (normal price £34.95) is available at £19.95 plus £4.95 p&p. and  ‘Writing Medico-Legal Reports in Civil Claims – an essential guide’  (normal price £69.95) is available at £50.00 plus £4.95 p&p only direct from the author by email to More information about the books and reviews are available at

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