What to Include in Instructions to a Forensic Expert

A clear letter of instruction is the foundation of effective expert evidence. Vague or incomplete instructions produce reports that miss the mark, require costly supplemental work, or expose the expert to criticism on admissibility and weight.

Core elements of the instruction letter

1. Parties and forum

Identify all parties, your client's role, the court or tribunal, case number and relevant procedural rules (CPR, arbitration institution rules, etc.). If the expert is appointed as SJE, state that expressly and confirm joint instruction arrangements.

2. Questions for the expert

Frame specific financial questions rather than asking the expert to "review everything." Examples:

• What was the claimant's lost contribution over the loss period?
• What assumptions are required to quantify business interruption loss under the policy wording (as legally defined)?
• Does the opposing expert's schedule double-count mitigation?

3. Documents

Provide organised disclosure - preferably indexed. Flag critical contracts, accounts, correspondence on mitigation and any prior expert reports. Native Excel files are often essential; PDFs alone may be insufficient for detailed quantum.

4. Legal framework

The expert does not advise on law, but needs to know the heads of loss pleaded and any legal constraints (e.g. remoteness, cap on damages, date of valuation). Counsel's note on legal issues is often invaluable.

5. Timetable

Court directions or arbitration orders for report exchange, expert meetings, supplemental reports and hearing dates. Late instructions compress quality - flag urgency realistically.

6. Fees and terms

Agree fee basis (hourly, staged, capped), payment terms and who holds the engagement (firm vs client). Confirm conflict checks have been requested.

CPR Part 35 compliance

Remind the expert that their duty is to the court. Instructions should not ask the expert to act as advocate. Avoid suggesting desired conclusions. It is appropriate to ask the expert to consider alternative scenarios where the factual matrix is uncertain.

Privileged advisory work

If the same firm has previously received litigation support from the expert on the same matter, disclose this at instruction so conflicts and role separation can be managed.

After instruction

Maintain a single point of contact where possible. Consolidate supplementary questions in writing. Keep the expert informed of material developments (e.g. new disclosure, settlement offers affecting scope).

Our intake process

We typically request an initial call with the fee earner, followed by written instructions and data transfer via agreed secure channels. See how to instruct us for contact details and our expert reports and testimony service.