Judges comment on expert evidence in almost every trial that turns on it, and most of that comment is neutral. Occasionally it is not. An expert finds their reasoning, their independence or their basic competence picked apart in open court, and then set out in a judgment that anyone can read. For the expert it is uncomfortable. For the solicitor who instructed them it can be expensive, and for the client it can be the reason the claim failed.
In short: judicial criticism runs on a scale. At the mild end a judge simply prefers the other side’s expert, which affects the weight given to one opinion and nothing more. At the serious end a judge finds that an expert has breached the duty owed to the court, and that finding can carry a costs order against the expert personally, a negligence claim from the party who instructed them, a regulatory referral, and a lasting problem in later cases. Almost every protection against it operates before the report is ever served.
Harley Street Legal prepares CPR Part 35 compliant reports for solicitors instructing on either side of civil litigation. What follows describes how the civil courts in England and Wales treat expert evidence. It is not a comment on the merits of any individual case.
What being criticised by the court actually means
There is no formal process called criticism. What happens is that a judge, in the course of deciding a case, explains which evidence was preferred and why. That explanation is often unflattering to somebody. A judgment might record that an expert strayed outside their field, argued a party’s case rather than answering the question, conceded a central point only under cross examination, or produced a report that did not say what the expert said in the witness box.
Those are different failures with different consequences. Lumping them together is how experts end up either ignoring a real warning or panicking about a passing remark.
The duty that criticism is measured against
Every finding about expert conduct starts from one rule. Rule 35.3 of the Civil Procedure Rules states that “it is the duty of experts to help the court on matters within their expertise”, and that “this duty overrides any obligation to the person from whom experts have received instructions or by whom they are paid”. The full text sits in Part 35 of the Civil Procedure Rules on the Ministry of Justice site.
Rule 35.10 then requires a report to state that the expert understands and has complied with that duty, and to disclose the substance of all material instructions. An expert who signs that statement and then behaves as an advocate has not merely performed poorly. They have made a statement to the court that the evidence contradicts, which is why judges treat partisanship far more seriously than a disputed clinical opinion.
Where criticism usually comes from
In practice the trigger is rarely the substance of the opinion. It is the way the opinion was constructed and defended. The recurring causes are an opinion that moves without explanation between the report, the joint statement and oral evidence, a refusal to concede anything at all, reasoning that cannot be traced back to the records, and evidence given on a topic the expert does not routinely practise in.
The last of those catches careful people out. An expert can be entirely competent in their own field and still be outside it by the time they are answering questions about causation, prognosis or the standard expected of a different specialty.
Criticism in a joint statement
Rule 35.12 allows the court to direct a discussion between experts so they can identify the issues and, where possible, reach an agreed opinion. The joint statement produced by that discussion is frequently where the damage is done, because it is the first document in which an expert has to justify a position to somebody who knows the subject as well as they do.
An expert whose position collapses in the joint statement, or who signs an agreement they later try to walk back at trial, has handed the other side a ready made line of cross examination. The same is true in reverse: a well reasoned joint statement often ends the argument without anyone giving oral evidence at all.
Criticism in the witness box
Oral evidence tests something a report cannot. It asks whether the expert can hold a reasoned position under pressure, concede what should be conceded, and explain the limits of their own opinion. Where the court directs concurrent evidence, described in more detail in our article on hot-tubbing and giving oral evidence, both experts answer the same question in sequence and the comparison is immediate.
Rule 35.14 is worth knowing here too. Experts may file written requests for directions to help them carry out their functions. It is used far less often than it could be, and it exists precisely so that an expert who is being asked to do something improper has a route to the court rather than a choice between their instructing party and their duty.
What a judge can do beyond critical words
The consequences scale with the finding. The table below sets out the pattern, though the categories overlap and the same judgment can contain more than one of them.
| Level of criticism | Typical trigger | Usual consequence |
|---|---|---|
| Preference for the other expert | Two tenable opinions, one better reasoned | Weight only. No finding against the expert |
| Adverse comment on reliability | Inconsistency, overstatement, poor preparation | Evidence discounted. Comment on the record in a public judgment |
| Finding of partisanship | Arguing the party’s case, selective use of records | Evidence rejected. Possible referral to a regulator |
| Finding of serious dereliction of duty | Fundamental incompetence or breach of the duty to the court | Costs order against the expert personally, on top of the above |
Costs orders against an expert personally
The court can order a person who is not a party to proceedings to pay costs. Applied to an expert, that turns a professional failure into a direct financial liability, and it is the consequence most experts underestimate.
The case usually cited is Thimmaya v Lancashire NHS Foundation Trust [2020] 1 WLUK 437. A consultant spinal surgeon instructed for the claimant was unable, in cross examination at a trial in 2019, to articulate the legal test for breach of duty in a clinical negligence case, and ultimately accepted that he did not know it. The claim was discontinued. In January 2020, at Manchester County Court, Her Honour Judge Claire Evans ordered him to pay £88,800 towards the defendant’s costs.
Two points from that case matter more than the figure. The first is that the expert’s clinical competence was never the issue. The second is that the threshold the court applied was not perfection but a serious dereliction of the duty owed to the court, which is a high bar and is meant to be.
Why experts can now be sued by their own side
Until 2011 an expert witness had immunity from being sued over the evidence they gave. In Jones v Kaney [2011] UKSC 13 the Supreme Court abolished that immunity in England and Wales. An expert whose negligent handling of a case causes loss to the party that instructed them can be sued by that party in the ordinary way.
That is the practical reason judicial criticism carries weight beyond reputation. A judgment recording that an expert abandoned a defensible position without explanation is close to a written record of the breach, and the instructing party has already paid for the consequences.
Regulatory consequences for a doctor
A doctor giving expert evidence is practising medicine for regulatory purposes. The General Medical Council’s guidance on providing witness statements or expert evidence as part of legal proceedings sets out what is expected, including working within the limits of competence and being honest about the extent of the evidence relied on.
A judge who considers that an expert has fallen short can refer the matter to the regulator, and a published judgment is available to anyone who wants to make that referral themselves. The wider regulatory framework, including the position of experts who are not on a professional register at all, is covered in our article on how expert witnesses are regulated in the UK.
What criticism does to later instructions
Judgments are searchable and opposing solicitors look. An adverse passage can be put to an expert in a later case, used to challenge their suitability at the permission stage, or raised in submissions on weight. It does not disqualify anyone, and one bruising trial does not end a medicolegal practice, but it becomes part of the material the other side works with.
It is also why an expert should disclose any previous adverse finding to an instructing solicitor at the outset, rather than letting it surface later.
How an expert reduces the risk before the report is served
Nearly all of the protection is built in at the drafting stage. Decline instructions outside your field, including the parts of a case that drift outside it. Set out the range of reasonable opinion rather than only the one you hold. Show the reasoning from the records to the conclusion so the route can be followed and, if necessary, disagreed with. State the limits of the material you were given, and keep the language of the report and of the joint statement consistent, because the gap between them is where cross examination starts. The structural detail is in our guide to writing a high quality expert witness report.
One further discipline. Know which role you are in. An expert who has been advising a party in an unpaid or informal capacity and then produces a Part 35 report has a problem that will be found, and the distinction is set out in our article on expert advisors and expert witnesses.
What an instructing solicitor should do about it
Where an expert has been criticised in an earlier case, read the judgment rather than the summary. The question is whether the finding goes to conduct or to a contested opinion, and whether it touches the field in which the expert is now being instructed. In a live case the questions are whether the opinion can still be supported, whether the criticism reaches the pleaded issues, and whether the position is better corrected in writing before trial than defended through it.
Frequently Asked Questions
Does a judge preferring the other expert count as criticism? Not in any meaningful sense. Two experts can hold tenable opinions and a judge has to choose between them. That choice goes to weight and carries no finding against the expert who was not preferred.
Can an expert be ordered to pay costs personally? Yes. The court can make a costs order against a person who is not a party. It is uncommon and the threshold is a serious dereliction of the duty owed to the court rather than an opinion the judge disagreed with.
Can an expert still be sued by the party who instructed them? Yes, since Jones v Kaney in 2011. The immunity from suit that expert witnesses previously held in England and Wales no longer exists.
Will a judge report an expert to their regulator? A judge can, and in a serious case may say so in the judgment. A published judgment is also available to anyone else who wishes to make a referral.
Does changing an opinion invite criticism? No, provided the change is explained. An opinion that moves because new material or another expert’s reasoning has justified the move is the duty to the court working as intended. An opinion that moves silently is what draws comment.
Instructing an expert who can withstand scrutiny
A report is only as useful as it is under cross examination. If you are weighing up an instruction in a plastic surgery, scarring, hand and upper limb or clinical negligence case, the expert witness services page sets out the scope of instruction, and you can submit an instruction directly.
Related reading
- How to Write a High Quality Expert Witness Report
- Hot-Tubbing and Giving Oral Evidence as an Expert Witness
- How Are Expert Witnesses Regulated in the UK?
This article is general information about civil procedure in England and Wales and is not legal advice or a clinical opinion on any individual case. The Civil Procedure Rules and Practice Direction 35 are amended from time to time, and case law develops, so check the current position before relying on anything mentioned here.