A court judges an expert report on whether it can be followed and trusted, not on how forcefully it argues. Practice Direction 35 sets out, in a numbered list, what a report has to contain, and much of the criticism experts attract in judgments comes from missing items on that list rather than from getting the clinical reasoning wrong. What happens once that criticism is on the record, and how far the consequences reach, is set out in our article on when an expert witness is criticised by the court.
In short: address the report to the court, work through the requirements of Practice Direction 35 in order, set out your instructions openly, keep fact and opinion visibly separate, deal fairly with any genuine range of opinion, and close with the prescribed statement of truth. Structure and candour carry more weight than style.
Prof. Sandip Hindocha, a Consultant Plastic Surgeon who prepares CPR Part 35 reports, writes to the same checklist a judge reads from, which is why the structure below follows the rules rather than a house template.
What a Court Is Actually Reading For
A judge reading expert evidence is trying to answer three questions. Is this person qualified to say what they are saying? Where did each fact come from? And can the route from those facts to the conclusion be retraced without taking anything on trust?
Everything that follows in this article is a way of answering one of those three questions on the page, before anyone has to ask it in cross-examination. A report that answers them well is easy to test, which is the point. Evidence that cannot be tested is worth very little to either side.
The Duty That Shapes Every Paragraph
Rule 35.3 of the Civil Procedure Rules puts it plainly. It is the duty of experts to help the court on matters within their expertise, and that duty overrides any obligation to the person from whom they received instructions or by whom they are paid.
Practice Direction 35 turns that principle into a drafting instruction. The report is addressed to the court, not to the solicitor who sent the papers. It is a small change of address that has a large effect on tone, because it removes any reason to write persuasively for one side. If you find yourself building an argument rather than setting out an opinion, the address line is the thing to re-read.
The same duty runs through the professional standards. The General Medical Council’s guidance on providing witness statements or expert evidence, in force since January 2024, applies to a doctor writing a report just as clinical guidance applies in the consulting room. How that sits alongside the court’s own rules is set out in more detail in our guide to how expert witnesses are regulated in the UK.
What Practice Direction 35 Requires
Paragraph 3.2 of Practice Direction 35 is the closest thing the rules give to a contents page. Treating it as a checklist rather than a description is the single easiest way to raise the quality of a report.
| Requirement | What it means on the page |
|---|---|
| Qualifications | Enough detail for the court to see the opinion falls inside your field, not an unexplained CV bolted on at the back. |
| Literature and material relied on | Named sources with editions and dates, so the reasoning can be checked rather than accepted. |
| Substance of all material instructions | Written and oral, summarised accurately, whether or not they assist the party who gave them. |
| Facts within your own knowledge | Marked as such, and kept apart from what you were told, sent or read. |
| Examinations and tests | Who carried out each one, under whose supervision, and with what qualifications. |
| Range of opinion | Where a genuine range exists, summarised with the reasons for the view you have taken. |
| Summary of conclusions | Short enough to stand alone and be read first. |
| Qualifications to an opinion | Stated openly wherever an opinion is provisional, conditional or incomplete. |
| Statement of duty | That you understand and have complied with your duty to the court. |
Setting Out the Instructions Without Editing Them
Rule 35.10 requires the report to state the substance of all material instructions, written or oral, on the basis of which it was written. Those instructions are not privileged in the ordinary way, and the court can allow them to be examined where there are reasonable grounds to think the statement of them is inaccurate or incomplete.
The practical consequence is that a tidy summary which quietly leaves out an awkward assumption creates a much larger problem than the assumption itself. Record what you were asked, what you were sent, what you were told on the telephone, and what you were asked not to consider. If a question was narrowed, say who narrowed it.
Keeping Fact and Opinion Visibly Separate
Practice Direction 35 asks the expert to make clear which facts in the report are within their own knowledge. That distinction is easy to hold in your head while writing and almost impossible for a reader to reconstruct afterwards, which is why it belongs in the layout rather than the prose.
Separate sections work better than careful sentences. A factual chronology drawn from the records, a section recording your own examination findings, then a section of opinion that refers back to both by paragraph number. When the reader can see where the boundary falls, they stop looking for it, and the opinion is read on its merits. The distinction between clinical work and evidential work is part of what the term medico-legal is describing.
Dealing With the Range of Opinion
Where there is a genuine range of opinion on a matter in the report, the rules require a summary of that range and the reasons for the expert’s own view. This is the requirement most often treated as optional, and it is the one that does most to make a report credible.
A range is not every view anyone has ever held. It is the body of responsible opinion a competent practitioner in the field could hold on the same material. Setting out the strongest version of the view you did not take, and then explaining why you did not take it, is a stronger position than not mentioning it, because the alternative will be put to you eventually.
The Statement of Truth
A report must be verified by a statement of truth in the form prescribed by Practice Direction 35, which begins with a confirmation that the expert has made clear which facts and matters referred to in the report are within their own knowledge and which are not.
Use the wording as it is given. Rewriting it into something that reads more naturally is a false economy, because the prescribed form is what a court is looking for and any variation invites a question about why it was varied. The statement also has to be true of the document it is attached to, so it is worth signing last, after the final version has been read through rather than before.
Writing So the Reasoning Can Be Followed
The reader is a lawyer or a judge, not a clinician. Technical vocabulary is not the problem, since a court is used to it, but unexplained technical vocabulary is. Define a term once, at first use, and then use it consistently rather than reaching for synonyms.
Numbered paragraphs throughout make the report usable in a way that nothing else does. They allow a solicitor to put a written question by reference to a paragraph, an opposing expert to identify a point of disagreement precisely, and a judge to cite the report in a judgment. A conclusion summary at the front, written so it can be read on its own, is the other structural change that repays the effort.
Staying Inside Your Own Competence
The duty in rule 35.3 is to help the court on matters within your expertise. The boundary of that expertise is therefore part of the evidence, and saying where it lies is a strength rather than an admission.
Two habits keep a report inside it. The first is to state, in the qualifications section, what you actually do and how often, rather than what your specialty covers in principle. The second is to name the point at which a question passes to another discipline, and to say so in the body of the report rather than leaving the reader to notice the silence.
Faults That Weaken an Otherwise Sound Report
Most weak reports are not wrong. They are unusable, and usually for one of a small number of reasons.
- Conclusions that appear without the intermediate reasoning that produced them.
- Records quoted at length in place of an analysis of what they show.
- Advocacy in the adjectives, where the facts themselves are neutral.
- A range of opinion section that records no range.
- Assumptions carried forward from the letter of instruction without being identified as assumptions.
- An opinion on a question of law, which is a matter for the court and not for the expert.
- No paragraph numbering, so nothing in the report can be referred to precisely.
Written Questions and Discussions Between Experts
A report is rarely the end of the process. Part 35 allows written questions to be put to an expert about their report, and any questions must be copied to the other party at the same time. The answers form part of the evidence, so they are written to the same standard as the report itself.
The court may also direct experts to discuss the issues and, where possible, reach an agreed opinion on them. The content of that discussion is confidential and is not referred to at trial unless the parties agree, and any agreement the experts reach does not bind the parties without their express consent. Neither the parties nor their legal representatives may attend, unless the court orders otherwise or all parties agree. Where a court instead appoints one expert for both sides, a different set of considerations applies, and those are covered in our article on the single joint expert. Where the court goes on to hear both experts together at trial, the joint statement usually becomes the agenda, which is explained in our note on hot-tubbing and concurrent expert evidence.
Declaring Any Use of AI
Transparency about how a report was produced is becoming part of what a court expects. The direction of travel, and what it is likely to mean for the way experts record their working methods, is set out in our article on how AI is changing expert witness reports.
The safe working assumption is the one the existing rules already imply. If a tool contributed to the substance of an opinion, the reader is entitled to know, because the statement of truth is a statement about your own professional opinion and not about a document you assembled.
Frequently Asked Questions
How long should a report be? There is no prescribed length. The rules ask for particular content, not a particular number of pages, and a report that covers the paragraph 3.2 requirements properly will find its own length. Padding a report with recited records makes it longer and less useful at the same time.
Should the report be addressed to the solicitor who instructed me? No. Practice Direction 35 says an expert’s report should be addressed to the court and not to the party from whom the expert received instructions.
What if my instructions were incomplete? Say so in the report, identify what was missing, and explain what effect the gap has on the opinion. An opinion given on partial material is acceptable if the limitation is stated. One that hides the gap is not.
Can I change my opinion after the report is served? Yes, and the duty to the court is the reason. If new material or an experts’ discussion changes your view, the change is communicated in writing without delay, with the reasons for it.
If you are instructing an expert and want to know how the process runs from the first letter through to a compliant report, our expert witness page sets out the scope of the work, and you can start the process on the instruct an expert page.
Related reading
- How Are Expert Witnesses Regulated in the UK?
- What Is a Single Joint Expert?
- How AI Is Changing Expert Witness Reports
This article is general information about the rules governing expert evidence in England and Wales. It is not legal advice and it is not a clinical opinion on any individual case. Anyone dealing with a specific claim should take advice from a qualified solicitor.