How to Instruct an Expert Witness: A Guide for Lawyers

Last updated: 5 October 2026

Photo: United Nations Day - Foreign, Commonwealth & Development Office

The quality of an expert witness report depends substantially on how the expert is instructed. A clear, well-prepared letter of instruction produces focused, useful evidence. A vague or leading instruction produces a report that fails to address the case's actual issues — or worse, looks like advocacy. This guide for lawyers sets out how to instruct expert witness properly, covering selection, the letter of instruction, document supply, working with the expert, and addressing common pitfalls.[1]

The guidance draws on UK Civil Procedure Rules Part 35, the Law Society Practice Note on Expert Witnesses (2022 update), ILPA Best Practice Guide, US Federal Rules of Evidence, Canadian Federal Court Rule 52.2, and the practical experience of legal practitioners working with country experts.

Step 1: Selecting the Right Expert

The first task is matching the expert to the case. Country experts vary in their specialism by region, profile, and methodology. Several factors should guide selection.[2]

• Regional specialism — does the expert cover the specific country and region your client is from?
• Profile-specific expertise — religious persecution, LGBTQ+, political opposition, military, gender-based?
• Language competence — does the expert read the relevant language sources?
• Recent fieldwork or research — when was the expert last engaged with the country?
• Court experience — has the expert given evidence before in the relevant jurisdiction?
• Independence track record — has the expert acknowledged weaknesses in past reports?

Step 2: Initial Contact and Engagement Terms

Initial contact should establish whether the expert is available, free of conflicts, and able to deliver in time. Key matters to confirm at this stage include the following.[3]

• Availability — can the expert deliver within the hearing timeline?
• Conflicts — does the expert have any conflict with the case or parties?
• Fees — what is the expected cost? Legal aid scope?
• Format — written report only, or also potential hearing attendance?
• Document handling — secure file transfer, confidentiality undertakings.
• Updates — willingness to produce supplementary reports if circumstances change.

Step 3: Drafting the Letter of Instruction

The letter of instruction is the single most important document in the process. A clear, neutral, focused letter produces a useful report. A vague or leading letter produces problems. Strong letters of instruction follow a recognisable structure.[4]

Step 4: Supplying Background Documents

The expert needs comprehensive background to produce a useful report. Provide the following.[5]

• Asylum statement — the client's account of events.
• Interview record — Home Office, USCIS, or IRB interview transcript.
• Decision letter — refusal letter or BIA decision setting out the issues.
• Any supporting documents — ID, court documents, medical records.
• Country information already in the case — CPINs, COI reports cited.
• Previous expert reports in related cases if relevant.
• Witness statements from family or community members.

Provide unfavourable as well as favourable materials. The expert needs the full picture. Omitting adverse material that later emerges damages the report's credibility.

Step 5: Working with the Expert During Preparation

During the preparation period, the relationship between solicitor and expert should be cooperative but properly distanced. Several principles guide this.[6]

• Answer factual questions the expert asks about the client's account.
• Do not direct opinions — let the expert reach their own conclusions.
• Share new developments — if country conditions change or new evidence emerges.
• Respect timing — agreed deadlines, but allow expert flexibility for complex issues.
• Maintain documentation of all instructions and exchanges.
• Avoid social or financial entanglements beyond proper fee payment.

Step 6: Reviewing the Draft

Most experts share a draft report before finalising. The review should cover factual accuracy, not opinions.[7]

• Factual errors — names, dates, places, citations — these can and should be corrected.
• Opinions and conclusions — must not be edited by the instructing party.
• Unclear language — can be flagged for the expert's own clarification.
• Missing engagement with case-specific facts — can be flagged for expert to consider.
• Compliance with court duties — confirm declaration is included.

The integrity of expert evidence depends on the integrity of the instruction process. A letter of instruction that frames neutral questions, provides complete background, and respects the expert's independence produces evidence that carries weight before tribunals. Shortcuts undermine the whole exercise.
Law Society Practice Note on Expert Witnesses (2022 update)

Common Pitfalls and How to Avoid Them

Conclusion

Instructing an expert witness is a structured process. The six steps — selection, engagement, letter of instruction, document supply, preparation collaboration, and draft review — together produce evidence that satisfies the standards UK, US, Canadian, and European tribunals apply. The integrity of the instruction process is fundamental to the integrity of the resulting evidence.

For practitioners, the practical task is to plan expert instruction early, draft neutral questions, supply complete background, and respect the expert's independence. See our wider Expert Witness Hub series: what is an expert witness, report contents section by section, what judges look for, and the practice direction.