An expert report is not a technical note with a declaration stapled to it. The rules set out what the court expects, and a report that meets them in substance passes the two tests that matter: the judge can follow it, and the other side can test every step and find it holds.

Civil proceedings: CPR Part 35

Part 35 and its Practice Direction, with the Guidance for the Instruction of Experts in Civil Claims, require that an expert’s evidence be the independent product of the expert, uninfluenced by the pressures of litigation; that the report state the substance of all material instructions; that it set out the facts and assumptions relied on, the literature and documents considered, and who carried out any test; that where there is a range of opinion it summarise the range and give reasons for the opinion held; and that it end with the statement of truth and the declaration of the expert’s duty to the court.

Every report from this practice is built around those requirements, and carries a section headed Matters adverse to those instructing me. It is not buried, and it is not negotiable. Sources are cited so that any figure can be checked. Assumptions are labelled as assumptions. Where the evidence supports a range and not a point, the range is given. Where a question falls outside vehicle engineering, the report says so and does not answer it.

Criminal proceedings: CrimPR Part 19

In criminal cases the expert’s duty to the court is the same, and the rules add to it. CrimPR Part 19 requires the expert to disclose anything of which they are aware that might reasonably be thought capable of undermining the reliability of their opinion or detracting from their credibility or impartiality, and to give details of any tests or experiments, who carried them out and under whose supervision, and the range of opinion on the matters dealt with. The declaration prescribed by the Criminal Practice Directions closes the report.

Instructions are accepted from the defence and the prosecution. Legally aided defence instructions are quoted in the form the Legal Aid Agency’s prior authority process needs, with court attendance costed at the same time.

Joint statements, questions and reviews

  • Joint statements with the other side’s expert, identifying what is agreed, what is not, and precisely why.
  • Written questions under rule 35.6, answered within the rules’ timetable.
  • Reviews of opposing reports, line by line: does the method hold, do the calculations reproduce, are the inputs sourced, is the opinion within the author’s expertise. The output is a structured note that an advocate can use directly in cross-examination.
  • Conferences and court attendance, in person or remotely.

How the practice checks its own work

Before any report is signed it goes through a fixed sequence: the papers are indexed and the gaps listed; each calculation is reproduced by a second method or a closed-form check; the draft is read again as a hostile expert would read it; and only then is it built, with working internal references, into the document that is served. The methods page shows what that discipline looks like in practice.