An expert is perfectly entitled to reach a strong opinion which supports the case of the party instructing them. The difficulty is when the reasoning appears to work the other way round, with the party’s case driving the expert opinion.

That distinction arose in KS v Secretary of State for the Home Department, where First-tier Tribunal Judge Froom considered expert evidence about conditions in Tajikistan. His criticisms ranged from whether the expert had demonstrated the necessary expertise through to the sources relied upon and the extent to which the appellant’s account had been independently examined. By the end of that analysis, the Judge’s view was that the expert was advocating for the appellant rather than providing critical and objective expert evidence.

The limits of an expert’s expertise

The expert described himself as a publicist, PR expert, television presenter and journalist specialising in Russia and post-Soviet states. He held degrees in international law and marketing and had written extensively for newspapers and websites.

The Tribunal was concerned about how much of that experience demonstrated expertise specifically in Tajikistan. Judge Froom noted that the expert did not appear to have visited the country, had held no academic post and listed only one publication, which concerned Russia. He concluded that sufficient expertise on Tajikistan had not been demonstrated.

This is an issue which can easily arise where someone has genuine expertise across a broad subject or geographical area. The question is not simply whether an expert is knowledgeable, but whether their knowledge and experience extend far enough to support the particular opinions they have been asked to give.

Checking the sources

Some of the most striking criticism concerned the source material.

The report stated that honour crimes were deeply ingrained in Tajik culture, particularly in rural areas, and cited four sources. Two dealt with domestic violence against women and the Tajik government’s response, another with religious freedom and the fourth was the Criminal Code of Tajikistan.

“I was not able to find any reference to honour crimes in any of these documents.”

Counsel was invited to identify such a reference and was also unable to do so. Judge Froom described the failure accurately to source the assertions about honour crimes as a “serious flaw in the report”.

The question of sources also arose in SU (Expert reports – format) Bangladesh [2026] UKUT 317 (IAC), which we considered in our article Online sources are not the expert opinion.

In SU, the Upper Tribunal emphasised that material relied upon should be identifiable and capable of being checked, and that experts should go back to the primary source wherever possible. The report must also distinguish between the underlying material and the expert’s own analysis and opinion.

KS illustrates the problem from a slightly different direction. Identifying a source is not enough if the source does not actually support the proposition for which it is being cited. The two decisions therefore fit rather neatly together. In SU, the emphasis was on making the source material transparent and traceable; in KS, the Tribunal was able to trace the sources and found that they did not support an important assertion in the report.

For experts who rely on academic papers, technical literature, industry publications, statistics or other external material, the practical discipline is much the same. The reader should be able to identify what has been relied upon, find it if necessary and understand what the expert says it establishes. A citation does not acquire authority merely by appearing in an expert report.

Assumptions and the client’s account

The Judge was also concerned about the way in which the expert dealt with information provided by the appellant.

Claims had been made about the influence of members of a particular family. The expert did not say that he had investigated those individuals or independently established the extent of their influence. Judge Froom said that the expert:

“simply accepts what the Appellant says and agrees with him”

and concluded that this did not assist the Tribunal.

Expert reports will often depend upon factual assumptions supplied by those instructing the expert. There is nothing unusual about that, and in many cases the expert will have no means of establishing those facts independently. What matters is being clear about the distinction between an assumed fact and something the expert has independently established, and not presenting the former as though it were the latter.

There is an interesting contrast elsewhere in the judgment. Judge Froom identified an issue concerning the alleged police search on which expert evidence might have assisted the Tribunal, but the report did not address it. The report therefore ventured into areas which concerned the Tribunal while leaving unanswered a question on which the expert might have been able to provide useful assistance.

When opinion becomes advocacy

Against that background, Judge Froom said:

“The distinct impression gained is that Mr Kharitonov is simply advocating on behalf of the Appellant”

rather than providing a critical and objective expert opinion. He went on to say that the expert “trespasses into the role reserved to the Tribunal”.

An expert does not preserve their independence by avoiding firm conclusions or carefully balancing every opinion. If the evidence leads strongly in one direction, the expert should say so. Independence lies in the process by which the opinion is reached: considering the relevant material, testing assumptions where appropriate, acknowledging the limits of the expert’s knowledge and allowing the evidence to determine the conclusion.

Seen together, the criticisms in KS explain why the Tribunal became concerned about advocacy. Questions about the expert’s specific expertise would not necessarily lead to that conclusion on their own. Nor would one poorly chosen citation. But where important assertions are unsupported by the sources cited, the client’s account is accepted without sufficient examination and opinions move into matters for the Tribunal, the cumulative effect can be rather different.

Judge Froom attached no weight to the report as expert evidence.

For anyone preparing an expert report, KS is a useful illustration of why independence has to be apparent throughout the report. It can be seen in the treatment of instructions and assumptions, in the selection and checking of sources, in recognition of the limits of the expert’s own expertise and, above all, in whether the reasoning genuinely leads to the opinion rather than being used to support a conclusion already reached.

Read the judgment: KS v Secretary of State for the Home Department on Find Case Law.

A recent Upper Tribunal decision gives some unusually practical guidance for experts who rely on material found online.

In SU (Expert reports – format) Bangladesh [2026] UKUT 317 (IAC), the Tribunal considered expert reports which drew heavily on publicly available internet material. The decision is particularly useful because it deals with something that now affects experts in many fields: how to use online source material properly in an expert report.

The Tribunal’s guidance is fairly straightforward, but important.

Where an expert relies on material found online, the source should be identifiable and capable of being checked. So far as possible, the expert should use the primary source rather than a secondary report about it. If material is quoted, it should be clearly identified as a quotation, with a link to the source and a translation where appropriate.

That is the sourcing side of the exercise.

But there is a separate point which is perhaps more important.

The material found online is not the expert opinion.

It is source material from which the expert may form an opinion.

The expert’s task is to consider that material, explain its relevance and significance, and then form and express an independent opinion based on it.

Both parts matter.

The underlying source material must be sufficiently transparent for the court or tribunal to understand where it came from and, where necessary, check it. But the report must also show the expert’s reasoning. The court needs to be able to understand how the expert moved from the underlying facts and sources to the opinion ultimately expressed.

It is then for the court or tribunal to decide what weight to give that opinion.

Primary sources matter

One point made expressly by the Upper Tribunal is that experts should, where possible, go back to the original source.

That may sound obvious, but it is increasingly easy to rely on a newspaper article, online summary, social media post or another secondary source which itself refers to an underlying document.

For an expert, that can create unnecessary uncertainty.

If a government statement, NGO report, technical paper, regulatory document or other primary material exists, there is obvious value in identifying and considering that material directly.

The Tribunal also stressed the importance of making quotation clear. Material copied from elsewhere should not appear in the report as though it were the expert’s own words.

That is not simply a matter of presentation. It enables the reader to distinguish between:

• the underlying source;
• the facts or information derived from it;
• the expert’s analysis of that information; and
• the expert opinion.

Those distinctions are central to a properly reasoned expert report.

The Academy’s own guidance on the Model Form of Expert Report reflects the same need to distinguish clearly between matters of fact and opinion.

Applying the material to the case

The Tribunal also made clear that a report should do more than set out general material.

Where the expert has been asked to consider the particular circumstances of a party, the report should apply the expert’s general conclusions to those particular facts.

That is an important part of what makes the evidence expert evidence rather than simply research.

A court can often read source material for itself. The value of the expert lies in the specialist analysis and opinion brought to that material.

That may involve explaining technical significance, identifying limitations, placing information in context, drawing on professional experience or explaining how apparently conflicting material should be understood.

The Academy’s What is an Expert Report? guidance similarly stresses that an expert report is not merely a statement of conclusions. The factual basis and reasoning leading to the opinion matter.

Responding to criticism

There is another useful practical point in SU.

Where one of the parties has raised concerns about an aspect of the expert report, the Tribunal said the expert should address those concerns directly, bearing in mind the overriding duty to assist the Tribunal on matters within the expert’s expertise.

That matters because an expert’s duty is not to defend the report at all costs.

If a legitimate criticism identifies an error, omission, weak source or assumption which needs reconsideration, the expert should deal with it.

The Academy’s Code of Practice for Experts places independence, impartiality, objectivity and integrity at the heart of expert practice.

A practical consequence of the online world

The volume of information available to experts has changed enormously.

In many fields, an expert can now locate hundreds of sources in a relatively short period. That can be extremely useful, but volume is not the same as quality.

The discipline lies in showing:

• what material has actually been relied upon;
• where it came from;
• why it is relevant;
• what the expert makes of it; and
• how it contributes to the opinion expressed.

That is why traceability matters.

The court or tribunal does not simply need an expert who can find information. It needs an expert who can analyse that information, explain it and give a properly supported opinion within their expertise.

That is the useful lesson from SU (Expert reports – format) Bangladesh.

Decision:
https://tribunalsdecisions.service.gov.uk/utiac/2026-ukut-00317

BAILII:
https://www.bailii.org/uk/cases/UKUT/IAC/2026/317.html

Related Academy resources

• Model Form of Expert Report
• What is an Expert Report?
• Code of Practice for Experts
• The Expert’s Report training

The High Court’s judgment in Various Claimants v Mercedes-Benz Group AG and others [2026] EWHC 1753 (KB) is a useful reminder that technical expertise, however impressive, is only part of the job of an expert witness.

The litigation involved a huge amount of highly technical expert evidence across a number of disciplines. What is particularly interesting is the contrast in the judge’s assessment of the experts themselves.

Some were praised for the quality and fairness of their evidence. Others attracted criticism over aspects of their compliance with Part 35.

That contrast matters because the experts involved were not lacking in technical expertise. They were experienced specialists dealing with complex issues in major litigation.

The point is rather that being an expert in your field and being an effective expert witness are not quite the same thing.

Under CPR Part 35, an expert’s role is to assist the court on matters within their expertise. That duty overrides any obligation to the person instructing or paying them.

Practice Direction 35 goes further. Expert evidence should be the independent product of the expert, uninfluenced by the pressures of litigation, and experts should consider all material facts, including those which might detract from their opinions.

Those requirements affect far more than the declaration at the end of a report.

They affect how the expert approaches the evidence in the first place.

An expert needs to be able to distinguish between what they know, what they have been told and what they have inferred. They need to consider material which may not support the position of the party instructing them. They need to explain the basis for their conclusions and, where appropriate, acknowledge that there may be a legitimate range of professional opinion.

Perhaps most importantly, they need to remain willing to reconsider their conclusions as the evidence develops.

That may sound elementary to experienced expert witnesses. But the significance of the Mercedes-Benz judgment is that these issues arose in extremely sophisticated litigation involving highly experienced specialists.

The technical complexity of the subject matter did not lessen the importance of the expert’s procedural and professional duties.

If anything, it made them more important.

Where the underlying issues are difficult for a court to evaluate without specialist assistance, the court is particularly dependent upon the expert presenting that specialist knowledge independently, fairly and in a way that can be understood and tested.

That is why the quality of expert evidence cannot be measured simply by the expert’s qualifications or standing in their profession.

The court also needs to be able to trust the process by which the opinion has been reached.

The Academy’s guidance on party-appointed experts reflects this. The expert’s role is to provide unbiased opinion within their expertise and not to assume the role of advocate.

The Academy’s Code of Practice for Experts similarly places independence, impartiality, objectivity and integrity at the centre of expert practice.

And because much of the expert’s evidence will ultimately be contained in the report, the Academy’s Model Form of Expert Report is designed to help experts present their reasoning in a form which assists the court. The Academy’s The Expert’s Report training also deals specifically with compliance, professional guidance and the practical preparation of expert evidence.

The broader lesson from the Mercedes-Benz litigation is fairly simple.

An expert witness brings two kinds of expertise to court: expertise in their professional field, and expertise in performing the role of an expert witness.

The first does not automatically provide the second.

Judgment

A High Court decision provides a useful warning for professionals who become expert witnesses in matters in which they have already been involved.

In MSA Properties Ltd v The Drapery Northampton Ltd [2026] EWHC 1420 (KB), the court had to resolve a dispute concerning deteriorated structural joists in a building in Northampton. Both parties relied on structural engineering evidence.

The point of wider interest for experts concerns the defendant’s expert, who had already been involved in the matter before the litigation.

He inspected the building in 2023 and produced a report for the defendant. That report was not prepared as expert evidence for the proceedings. By 2025, however, he was acting as the defendant’s expert witness.

That change of role became important.

The judge noted that the later expert report did not refer to the earlier inspection or the report produced at the time, despite the expert accepting in oral evidence that the earlier inspection had given him a better view of the joists.

The court was also critical of the extent to which he had engaged with the available evidence and of the opportunities available to him to inspect the property more fully.

The most significant criticism was the judge’s observation that his approach reflected:

“some conflation of his role as a contractor engaged in negotiations with the Claimant and his duties as an expert witness”

There was no suggestion that the expert had deliberately acted partially. The concern was rather that aspects of his earlier role appeared to have carried over into the way he approached his later expert evidence.

That is a useful warning for any professional who changes role during the life of a dispute.

Previous involvement does not automatically prevent someone from later acting as an expert witness. In some cases, that earlier involvement may mean they have valuable knowledge of the subject matter.

But the nature of the role changes.

A contractor, consultant or adviser may previously have been helping a client solve a problem, negotiate a position or achieve a particular commercial outcome. An expert witness has a different duty.

Under CPR 35.3, an expert’s duty is to help the court on matters within their expertise. That duty overrides any obligation to the person from whom they have received instructions or by whom they are paid.

That is not simply a formal statement to be repeated in the declaration at the end of a report. It has practical consequences for the way an expert approaches the evidence.

Transparency about previous involvement

Where an expert has already inspected the subject matter, produced reports, advised a party, taken part in negotiations or expressed views before being instructed as an expert witness, that history may be material to the opinion now being given.

The point is not that every earlier conversation or document must automatically be reproduced. It is that relevant prior involvement should not be left invisible if it bears on the expert’s present reasoning.

That is particularly important because CPR 35.10 requires an expert report to state the substance of all material instructions, whether written or oral, on the basis of which the report was written. Practice Direction 35 also requires the expert to make clear which facts are within their own knowledge and which have been provided by others.

In this case, the earlier involvement was not peripheral. The expert had inspected the joists at a time when they were more fully exposed and had produced an earlier report. He later accepted that the earlier inspection had given him a better view of the joists, yet neither the inspection nor the earlier report appeared in his expert report.

That is a useful illustration of why disclosure matters.

If earlier involvement has informed what the expert knows, assumes or concludes, the court should be able to see that route clearly. If it only emerges later, particularly in cross-examination, the omission can create an avoidable question about the completeness and transparency of the expert’s reasoning.

For an expert changing role, a sensible question at the outset is:

What have I already done, seen, said or concluded in this matter, and what of that is material to the opinion I am now giving?

If someone changes role during the life of a dispute, earlier assumptions may need to be revisited. Previous opinions should not simply be carried forward without being tested against the evidence now available. Earlier inspections, reports and involvement may themselves be relevant and should be dealt with openly where necessary.

The wider framework of the Civil Procedure Rules matters as well.

The overriding objective in CPR 1.1 is to enable the court to deal with cases justly and at proportionate cost. Expert evidence forms part of that process. It is therefore not enough for an expert merely to possess relevant expertise. The evidence has to assist the court in a way which is independent, properly reasoned and proportionate to the issues in dispute.

That is why a change in role can be important.

A professional may quite properly have spent months or years advising a client, negotiating with another party or working towards a particular practical outcome. Those activities may require judgement, persuasion and a close identification with the client’s interests.

The expert witness role is different.

Once instructed as an expert, the professional must be able to step back from that earlier involvement and approach the evidence independently. That may mean reconsidering previous views, acknowledging matters which do not support the client’s position and making clear where earlier involvement has informed the present opinion.

• The Academy’s guidance on party-appointed experts explains the overriding duty owed by an expert to the court.
• The Academy’s Code of Practice for Experts places independence, impartiality, objectivity and integrity at the heart of expert practice.
• The Academy’s Model Form of Expert Report is also relevant where an expert has had previous involvement, because the report should make clear the factual basis of the opinions expressed and the material relied upon.

The lesson from MSA Properties is not that previous involvement disqualifies an expert. It is that a professional who moves from contractor, adviser or negotiator to expert witness must make that transition consciously and transparently. The court may look closely at whether the expert has genuinely separated the new role from the old one, and whether the report gives a clear account of any earlier involvement which bears on the opinion now being expressed.

For experts, that is a useful point to consider before accepting instructions in a matter in which they have already been involved.

See the judgment here on BAILII.

Anthropic has just announced that Claude will start leaving an invisible mark in the text it generates, in an announcement that may have unintended consequences for expert witnesses.

Supported Claude models will embed machine-readable watermarks into generated text. Anthropic says those marks will travel with the words when copied and pasted into other documents and may survive subsequent editing.

The immediate purpose is provenance. As the volume of AI-generated material increases, watermarking offers a potential means of identifying content that has passed through a particular AI system.

For expert witnesses, however, that raises a rather more difficult question: if an expert report contains an AI watermark, what exactly does that prove?

Perhaps less than might first appear.

Detection is not the same as authorship

One of the most important qualifications comes from Anthropic itself.

Anthropic cautions that detecting its watermark does not establish that Claude wrote or originated the material. Rather, it indicates that the content may have been processed by Claude.

That distinction could be particularly important in expert evidence.

An expert might write an entire report themselves and subsequently ask an AI tool to correct spelling and grammar. Another might use AI to improve the structure of material they have already written. A third might provide their analysis and ask an AI system to turn it into polished prose.

Those activities are quite different from asking an AI system to examine the underlying evidence, perform the analysis and suggest the opinion the expert should express.

Yet all involve AI-generated or AI-processed text.

Consider four possible uses:

• An expert writes their report and uses AI to check spelling and grammar.
• The expert writes the substance but asks AI to improve its structure or expression.
• The expert provides their analysis and asks AI to draft passages expressing it.
• The expert asks AI to analyse the evidence and assist in formulating the opinion.

All involve AI, but they plainly do not raise the same questions about the independence of the expert’s analysis and opinion.

That makes the presence of a watermark potentially useful evidence, but not necessarily evidence of what might initially be assumed.

Provenance of the text is not provenance of the opinion

This is perhaps the central issue for expert witnesses. A watermark may provide evidence about the provenance of the words. It might indicate that Claude, or another AI system using similar technology, has been involved in generating or processing them:

• It cannot, by itself, establish the provenance of the opinion.
• It does not tell us who examined the evidence.
• It does not tell us who identified the relevant issues.
• It does not tell us whether the expert carried out the underlying calculations or analysis.
• And, most importantly, it does not tell us whether the conclusion was independently reached by the expert or suggested by an AI system.

The same paragraph could conceivably carry an AI watermark whether Claude corrected three grammatical errors in it or generated the paragraph from scratch.

For expert evidence, those are very different propositions.

The absence of a watermark proves little too

There is also a problem in the opposite direction.

No watermark does not necessarily mean no AI.

Anthropic acknowledges that detection can become more difficult where generated material has subsequently been heavily edited, paraphrased, translated or combined with other text. A passage may also simply be too short to provide sufficient information for reliable detection.

This creates an important limitation if watermark detection ever begins to be used when examining expert reports.

A positive result may indicate AI involvement without establishing the extent or nature of that involvement whilst a negative result cannot necessarily establish that there was no AI involvement at all.

Watermark detection should therefore not be treated as a binary test of whether an expert “used AI”.

A new question in cross-examination?

The development also raises an interesting practical possibility.

“Your report contains a watermark indicating that it was processed by Claude. How did you use it?”

The answer might be entirely unremarkable.

The expert might explain that they wrote the report themselves and used Claude to check its grammar. They might explain that they used it to condense a lengthy passage they had already written. Alternatively, the answer might reveal that AI played a much greater role in analysing material or formulating the opinions contained in the report.

The takeaway is that whilst the watermark itself cannot distinguish between those situations, it may, however, provide the starting point for questions which can.

That means the increasingly important question may not simply be:

“Did you use AI?”

It may instead be:

“Precisely how did you use it?”

Watermarking is becoming a real technology

Anthropic is not alone in pursuing this approach.

Google has already developed SynthID Text, a watermarking technology for AI-generated text. Rather than inserting a visible label or conventional metadata, SynthID subtly affects the model’s choice of tokens as text is generated. Across a sufficiently long passage, those choices create a statistical signature which can subsequently be detected.

Anthropic has not publicly confirmed that Claude’s watermark uses the same technical method, so the two systems should not be assumed to work identically.

The significance is broader. Text watermarking is moving beyond academic research and into mainstream generative AI products.

If the technology becomes widespread, lawyers, courts and experts may increasingly encounter claims that a document has been identified as having passed through an AI system.

Understanding what such a finding does, and does not, establish will therefore become important.

The expert remains responsible

The Academy’s guidance on the use of Artificial Intelligence by expert witnesses already addresses the more fundamental issue.

AI can be a useful tool, but it cannot substitute for the expert’s own expertise, analysis and opinion. Experts remain responsible for the evidence they give. Where AI has played a significant role, keeping appropriate records of how it was used may also become increasingly important, particularly if the expert is subsequently required to explain that use in court.

Watermarking adds another dimension to that responsibility.

It may make some uses of AI more readily identifiable. But identifying that an AI system touched the words is not the same as establishing who produced the intellectual work behind them.

For expert evidence, that distinction is crucial.

Provenance of the text is not necessarily provenance of the opinion.

As AI provenance technology develops, the ability of an expert to explain what the AI did, what the expert did, and where the opinion actually came from may become increasingly important.

In Trinsic Collagen Ltd v Procoll Ltd [2026] EWHC 1793 (Ch), the court criticised the way additional information had been provided to the claimant’s experts and then relied on without being clearly identified in the reports, or in one instance the joint statement.

The issue was not that the experts had spoken to the client. It was that the factual basis of their conclusions was not always transparent.

For an expert report to assist the court properly, the reader should be able to see the route from the facts and assumptions, through the analysis, to the opinion reached. That means being clear about material obtained through discussions, site visits, correspondence or subsequent instructions, especially where it influences the expert’s reasoning.

The Academy’s own guidance reflects the same principle. An expert report should contain a concise statement of the facts and assumptions used, followed by the expert’s analysis and opinion, with fact and opinion clearly distinguished.

A useful question before signing a report is this: could another expert, or the judge, identify every material fact and assumption on which my conclusion depends? If not, the report may need another look.

The Academy’s Model Form of Expert Report also reflects this approach.

Not later. In the report.

If an expert opinion depends on incomplete data, assumptions or qualifications, those limitations belong in the written report.

1. Not in cross-examination.
2. Not in re-examination.
3. Not only after the tribunal asks the right question.

In Mew v General Dental Council [2026] EWHC 1116 (Admin), the High Court considered expert evidence given during professional disciplinary proceedings.

One expert had deliberately avoided setting out limitations in the available data, believing that they could instead be explained when he gave oral evidence.

Charles Bagot KC, sitting as a Deputy High Court Judge, said that this revealed a “fundamental misunderstanding” of the obligations of a CPR-compliant expert.

The problem was not that the evidence required qualification. Many expert opinions do.

The problem was that the qualification had been withheld from the report.

A court or tribunal must be able to understand:

• what the expert can conclude;
• what the expert cannot conclude;
• where the evidence is uncertain; and
• how those limitations affect the strength of the opinion.

A carefully expressed qualification does not weaken expert evidence. It allows the decision-maker to assess it properly – and will often make the opinion more credible.

The expert report should contain the opinion the expert can genuinely support, not an unqualified version that appears more persuasive on first reading.

Read the judgment:
https://www.bailii.org/ew/cases/EWHC/Admin/2026/1116.html

“The expert had only skimmed the papers.”

Few expert witnesses would want to read those words in a judgment.

In Re X and Y (Care Proceedings: Publication of Judgment: Criticism of Expert Witness) [2026] EWFC 132, Mrs Justice Knowles decided that the consultant neurosurgeon should be identified following serious criticism of his conduct as an expert witness. That decision followed the court’s detailed findings in Re X and Y (Care Proceedings: Fact Finding: Death of a Child: Expert Evidence) [2025] EWFC 132.

The criticism went far beyond inadequate preparation.

The court found that the expert had not properly engaged with the available evidence, had strayed beyond the limits of his expertise, had failed to engage adequately with the opinions of other experts, and had advanced conclusions based on speculation rather than a sound evidential foundation.

The case is a reminder that expert evidence is judged not only by the conclusions reached, but by the process used to reach them.

An expert opinion carries weight because it is the product of careful preparation, objective analysis and transparent reasoning.

Before accepting an instruction—or before entering the witness box—it is worth asking:

✔️ Have I fully engaged with all the relevant material?

✔️ Am I remaining firmly within my own expertise?

✔️ Have I fairly considered competing expert opinions?

✔️ Can I clearly explain the evidential basis for every conclusion I have reached?

The role of an expert witness is not to persuade. It is to assist the court with independent, balanced and properly reasoned evidence.

📖 Judgments:

Re X and Y (Care Proceedings: Publication of Judgment: Criticism of Expert Witness) [2026] EWFC 132
https://www.bailii.org/ew/cases/EWFC/HCJ/2026/132.html

Re X and Y (Care Proceedings: Fact Finding: Death of a Child: Expert Evidence) [2025] EWFC 132
https://www.bailii.org/ew/cases/EWFC/HCJ/2025/132.html

 

Some specialist areas of expertise are so niche that it’s almost impossible to find experts who are free of previous involvement with one or more parties to a dispute. In a recent case requiring expert evidence in mine surveying (Cleveland Potash Ltd v Drummond & Ors) not only had both experts been involved with the parties they had worked in the same office as each other for 20 years!

In this case both experts were clear and transparent about their previous involvement and as the  judge explained, “Whilst neither party raised any concerns about the experts’ prior and ongoing involvement in the issues related to this dispute I will have to consider that involvement as part of my overall assessment of the experts. I remind myself that the experts have an overriding duty to the court which should override their duty to their clients.”

It seems that one expert was much more successful in retaining her objectivity than the other, reading the judge’s explanation gives some important pointers for all experts as to how to do this, specifically;

“Mrs Iwanicki was a very impressive witness. She was deeply knowledgeable about her subject. She gave clear, careful, well considered and measured answers to the questions she was asked. She had a good understanding of her overriding duty to assist the court rather than to advocate for a particular position. Her answers were honest and straightforward even where those answers might have been seen as providing some assistance to Rs. That is what the court expects of an expert witness who understands that their role is not to advocate for a particular party or outcome but to assist the court.

 

Mr Troman was also clearly very knowledgeable about his subject, however, unlike Mrs Iwanicki on some occasions he did not appear able to disassociate his longstanding role of assisting the Rs (and other leaseholders) to negotiate what he considered to be a satisfactory outcome with CPL from his duty to assist the court. This more partisan approach had infected some of his evidence and the contents of his report. It was clear from his evidence that he felt that other mineral rights owners who had now agreed terms with CPL should have held out and/or would have done better if they had followed his advice/recommendations. He was reluctant to accept the possibility that the conclusions in his report might need to be adjusted or modified even when it became apparent that there were factors or information that he had not known about and could not therefore have taken into account when reaching his conclusions. His resistance to accepting any possibility that his conclusions on valuation might need to be adjusted was unhelpful and undermined his position. Further he had a tendency to speculate both in his report and in his evidence and on at least one occasion asserted a factual position which turned out not to be true. Overall, this approach undermined his credibility and the weight that I give his expert opinion.

 

As always the key for any expert is to ask yourself ‘what would I say if I was acting for the other side?’. If the answer is in any way different then you need to think again. For guidance on what to do if you have been involved with a party to a dispute and other issues relating to conflicts or perceived conflicts see our guidance on the subject.

Our image is from the New Scientist

 

The High Court ruling against Danish tax authority SKAT in a £1.4 billion dividend tax fraud case has been widely reported, not least because the judge concluded that SKAT’s controls on the transactions involved were so flimsy as to represent the equivalent of a ‘help yourself’ sign outside a bank.

 

Less attention has been given to the judge’s criticisms of the experts who appeared on behalf of the many parties involved. As he put it “ All three experts, in differing ways, did not provide properly balanced written reports”.

 

Perhaps the clearest example was SKAT’s expert “whose written work was argument rather than expert evidence” showing the dangers of working closely with a client and legal team on complex, long-running litigation. The judge concluded that “he finds it difficult not to think and express himself as an advocate for SKAT’s position. He has, I think, lost detachment from the partisan interests of SKAT” and was unable perhaps to hear any ‘evil’ in his client’s case.

 

Somewhat less concerning was an expert whose testimony was careful but tended to obscure his views and maximise differences with other experts that were not a pronounced as appeared at first glance.  As the judge observed, “That exposed him to a cross-examination that should have been largely unnecessary to confirm the extent to which, in substance, he agrees with a range of matters on which SKAT relied. “ Fortunately he appears to have dealt with that cross-examination impressively, fairly (with balance), and with an obvious depth of thought and expertise. A better approach might have been to write a report that allowed the parties to see more clearly.

 

And finally, the third expert’s generally much better approach (once his reports had been edited to remove contentious factual matters that should not have been there!) and thoughtful and fair answers to questions were undermined by his taking a view in the witness box that he had not expressed in writing.  The judge concluded that his interpretation of a key terminology expressed in oral evidence “had not been his view at any material time. It was inconsistent with the views he had expressed in writing, including in his primary expert report in these proceedings, to which he had to proffer alterations when called to give his oral evidence to advance the different view. “  While the case did not turn on this point the judge made it clear that speaking out in this way, because his written views in fact assisted the other side, was not acceptable and did the expert no credit.

 

The message to experts should not be a surprise, no client’s case is perfect and there are times when your views will not support their case. When that happens it is critical that you make sure your client’s hear you, that the court can see hat your views really area and that when you speak you keep your duty of independence firmly in mind.

Anyone considering acting as an expert needs to understand that environment,  the rules that apply to expert evidence and how to avoid the pitfalls that can lead to a difficult time in court and potentially public criticism from a Judge.

The Academy’s training programme is designed to help already  skilled professionals through the basic foundations to a mock cross-examination to ensure that they are fully prepared. Our training courses are primarily delivered online but we run some face to face courses  in London and Hong Kong. We can also run in-house training for larger consultancies, please contact us for details.