How to Instruct an Expert Witness: A Step-by-Step Guide for Solicitors

Summary

• You must get the court’s permission before relying on an expert’s report or calling them to give evidence (though you may consult an expert privately without prior permission).
• Draft the specific questions the expert must answer before you contact anyone, not after.
• Confirm current registration, active practice in the precise issue, and any conflicts, in writing, before instruction.
• Send a complete, indexed bundle in one go, and flag any missing records explicitly.
• Missing the court’s directed deadline for the report puts your evidence at risk of exclusion under CPR 35.13.

If you are instructing an expert witness for your case, it is important to understand the exact process required by the Civil Procedure Rules. In almost every civil claim you need the court’s permission before you can rely on an expert’s report or oral evidence. CPR 35.4 makes this a precondition, and CPR 35.1 restricts expert evidence to what is reasonably required to resolve the specific issues in dispute.

Before requesting permission from the court

As recommended by the Civil Justice Council, before instructing an expert or asking the court for permission to appoint one, check that the expert:

• Has the right skills and experience for this specific case;
• Understands the general duties an expert owes to the court;
• Can deliver a report, answer questions and take part in expert discussions within a reasonable time and at a proportionate cost;
• Is available to attend trial if needed; and
• Has no potential conflict of interest.

The following should also be confirmed early in the process:

• The capacity the expert will be appointed in (for example, party-appointed or single joint expert);
• The services required (such as a written report, answering questions, or attending meetings and court);
• The deadline for delivering the report;
• How fees are calculated (hourly or daily rate plus an estimated time, or a fixed fee), noting that parties must give the court a costs estimate for the expert evidence at each stage of proceedings under CPR 35.4(2);
• Travel expenses and other disbursements;
• Cancellation charges;
• Any fee for attending court;
• When payment is due;
• Whether a third party will pay the fees; and
• If the case is publicly funded, whether the expert’s charges will be assessed.

What should the letter of instruction contain?

Solicitors instructing experts should give clear instructions, with the relevant documents attached, covering:

• Names, addresses, phone numbers, dates of the incident and any claim reference numbers;
• The type of expertise needed;
• The purpose of the advice or report, what needs to be investigated, the issues involved, and who the parties are;
• The statements of case, disclosure documents, witness statements and other expert reports relevant to the report, making clear which have been served and which are still drafts, along with when the drafts are likely to be finalised;
• If proceedings have not yet started, whether they are likely to, and whether the expert is only being asked to give advice at this stage;
• A proposed timetable for each stage of the expert’s work, in line with good case management and the expert’s own availability; and
• If proceedings have started, the dates of any hearings (including case or costs management conferences and pre-trial reviews), the deadlines for exchanging expert reports, the court name, claim number, case track, and whether there is a set budget for expert fees.

Where practicable, instructing parties should also try to agree the instructions between themselves and make sure each expert receives the same factual material.

A letter of instruction should be tailored to the specific facts and legal context of each case, since the questions asked, the evidential disputes flagged, and the standard of proof applied all vary according to what the report is actually for. For example, in a clinical negligence claim, a letter of instruction sets out the relevant medical history, specific hospital admissions, and whether any shortcomings breached the duty of care and caused the injury.

Practice Direction 35 requires the finished report to give details of the expert’s qualifications, list the literature or material relied on, and contain a statement confirming the expert understands their duty to the court and has complied with it. As the Practice Direction itself states: “Expert evidence should be the independent product of the expert uninfluenced by the pressures of litigation”.

A letter of instruction that pre-empts the answer undermines that independence before the work has even started, and a court can strike out or discount a report where the letter shows signs of having steered the conclusion.

Acceptance of instructions

Experts must promptly confirm whether they accept an instruction and speak up straight away if any problems arise. This includes flagging any instructions that fall outside their expertise, are unrealistic on timing, or are unclear (requesting clarification and declining to act until they get it); telling the instructing party if they think the information they’ve been given is insufficient to complete the work, if they may not be able to meet the agreed terms, if the instructions put them in conflict with their duties as an expert, or if they doubt they can comply with a court order.

Experts must never give an opinion outside their own field, or accept instructions asking them to, and if they notice their instructions differ from those given to another expert on the same case, they need to say so. Fees should be agreed directly with the instructing party, bearing in mind that the expert may need to provide a costs estimate to the court, and that the court can limit what is recoverable.

How do you check the expert is right for this case?

Confirm current professional registration and that the expert’s active clinical or technical practice matches the exact issue in dispute, not just the general discipline. A cardiologist who stopped clinical practice a decade ago is quite different from one seeing the relevant condition weekly.

Ask directly, in writing, whether the expert has any prior relationship with a party, a financial interest in the outcome through a shareholding or consultancy, a public position already stated on the issue through articles or prior cases, or an existing instruction in related proceedings. A short conflict check costs nothing at this stage. Discovering a problem after the report has been served, when the other side raises it in cross-examination, costs considerably more in time and in the report’s credibility.

What records does the expert need?

The expert needs a fully indexed, paginated bundle sent in one go, not a partial file with more material promised later. An expert working from incomplete material produces an opinion with gaps that the other side’s counsel will find quickly.

A typical bundle includes the letter of instruction, the pleadings or documents identifying the issues in dispute, relevant witness statements, and the technical or clinical records needed to answer the specific questions asked. Where records are missing or incomplete, note that explicitly in the instructions, so the expert’s opinion reflects the actual limits of the evidence rather than papering over a gap the other side will expose later. That is the difference between an opinion that survives scrutiny and one that collapses under a single well-aimed Part 35 question.

What happens if you miss the court’s deadline?

Missing the directed date for serving an expert report puts your evidence at risk under CPR 35.13, which provides that a party who serves late may not rely on the report at trial without the court’s permission. That permission is not automatic and depends on the reason for delay and the prejudice to the other side.

Diarise the deadline with the expert in writing at the point of instruction rather than assuming it will be tracked independently. Where a delay looks likely, apply to extend the deadline before it passes, not after. A court weighing a late application after the event has far less reason to be sympathetic than one weighing a request made while there is still time to accommodate it.

 

Final words

Instructing an expert witness runs on a clear sequence: secure the court’s permission before relying on any report, vet the expert’s registration, expertise and conflicts before contacting them, set out terms and fees in writing at the outset, and send a complete, tailored bundle in one go. Once instructed, the expert carries their own duty to flag problems early, whether over scope, timing, or a conflict, so the instruction stays workable on both sides.

 

Frequently asked questions

Do I need the court’s permission for every expert report?

Yes, in almost every civil claim you need the court’s permission under CPR 35.4 before instructing an expert or relying on their report at trial. Small claims track cases follow a more limited procedure, so check the applicable track before assuming the general rule applies.

Can I tell the expert what conclusion I am hoping for?

No, your letter of instruction must never suggest a preferred outcome. Practice Direction 35 requires the expert’s opinion to be independent and uninfluenced by the pressures of litigation, and a letter that steers the answer can undermine the report’s standing in court.

What if I discover records are missing after instruction?

Tell the expert in writing as soon as you know, and ask them to note the gap in the report rather than working around it silently. An opinion that flags its own evidential limits withstands cross-examination far better than one that does not.