Section 1
Purpose
Expert Reports are formal documents prepared by a qualified and independent expert to assist a tribunal (adjudicator, arbitrator, or court) in understanding technical, financial, or valuation matters that require specialist knowledge beyond the competence of a non-expert decision-maker. In construction disputes, QS experts are frequently instructed to provide expert evidence on quantum — the valuation of variations, the assessment of loss and expense, the calculation of liquidated damages, and the quantification of defect remediation costs.
RICS Expert Witness PS (2nd ed., effective 2 January 2018) is a mandatory professional statement that governs the conduct of RICS members acting as expert witnesses. The overriding duty of the expert is to the tribunal, not to the instructing party. An expert who allows their opinion to be influenced by their client's commercial interests is in breach of both the RICS PS and the CPR Part 35 obligations (in litigation) — and risks both professional sanctions and contempt of court.
The QS must distinguish between the role of expert witness (independent, duty to tribunal) and the role of party representative or quantum advocate (acting in the client's interests). These are mutually exclusive roles on the same matter.
Section 2
Key Principles
- RICS Expert Witness PS (2nd ed., effective 2 January 2018): the expert's primary duty is to the tribunal, not the instructing party; the expert must be independent, objective, and not allow their opinion to be influenced by advocacy considerations.
- CPR Part 35 (in High Court/TCC litigation): expert evidence requires court permission; the expert report must include a statement that the expert understands their duty to the court and has complied with it; the expert may be cross-examined.
- Adjudication: expert evidence in adjudication is less formally regulated than in litigation, but RICS Expert Witness PS still applies; adjudicators are familiar with the PS and will discount evidence that appears partial or unsupported.
- ICC Arbitration / Construction Industry Arbitration: expert witnesses in arbitration proceedings must comply with the procedural rules of the relevant arbitration institution and the RICS Expert Witness PS.
- Expert discussions and statements of agreed/unagreed issues: in many proceedings, experts from each side are required to meet and produce a joint statement identifying areas of agreement and areas of disagreement; this process narrows the issues for the tribunal.
- Shadow expert: the QS may be instructed as a 'shadow expert' — advising the party's legal team on the opposing expert's evidence without producing a report or being identified to the tribunal; this is a legitimate role but must be clearly distinguished from the expert witness role.
Section 3
Practical Application
Step 1
On receipt of instructions as expert witness: confirm the scope of the instruction; confirm independence (no conflict of interest with either party); confirm the format required (adjudication, arbitration, litigation); confirm the fee basis (should not be contingency-based — this compromises independence).
Step 2
Prepare the expert report structure: (i) introduction and instructions received; (ii) documents reviewed; (iii) issues to be addressed; (iv) expert's analysis for each issue; (v) conclusions; (vi) statement of truth; (vii) RICS Expert Witness PS compliance statement.
Step 3
Address each issue in the expert's terms — the expert provides opinion on technical/financial matters; legal submissions are for the lawyers; the expert should not comment on the merits of the legal argument, only on the quantum or valuation issue.
Step 4
Cross-reference all opinions to supporting evidence; never state a conclusion without the basis for it; identify assumptions made and the impact if the assumption is wrong.
Step 5
Attend expert discussions as required; prepare for the meeting by identifying clearly which points are truly in issue and which may be agreed; produce the joint statement accurately reflecting the meeting's conclusions.
Step 6
Prepare for cross-examination: be able to explain and defend every opinion in the report; do not change opinions under pressure unless genuinely persuaded by new information or argument; maintain the duty to the tribunal at all times.
Step 7
After the proceedings, review the tribunal's decision on the quantum issues — what was accepted and what was rejected, and why; use the feedback to improve future expert work.
Section 4
Common Mistakes to Avoid
- Allowing the instructing party to dictate the expert's conclusions — this destroys the independence that gives expert evidence its evidential weight; the instructing party can brief the expert, but cannot direct the expert's opinion.
- Accepting a contingency fee arrangement — under RICS Expert Witness PS, expert fees should not be contingent on the outcome of the case; contingency arrangements compromise independence and are prohibited.
- Failing to disclose all documents reviewed, including those adverse to the instructing party's case — the expert must disclose all material documents reviewed, not just those supporting the instructed party's position.
- Overstepping the expert's area of expertise — the QS expert on quantum should not opine on legal entitlement or on technical engineering matters outside their competence; identify the limits of expertise and state them clearly.
- Failing to produce a compliant statement of truth — the statement of truth is mandatory under CPR Part 35 and RICS Expert Witness PS; absence or non-compliance is a procedural defect that weakens the report's admissibility.
Section 5
APC Competency & Quick Reference
- Conflict Avoidance, Management and Dispute Resolution Procedures Level 3 — expert witness obligations, CPR Part 35, RICS Expert Witness PS
- Legal and Regulatory Compliance Level 2 — expert duty to tribunal, CPR, arbitration rules
What is the overriding duty of an expert witness and to whom is it owed?
The overriding duty of the expert witness is to the tribunal — the adjudicator, arbitrator, or court. This duty overrides any obligation to the instructing party. Under RICS Expert Witness PS (2nd ed., effective 2 January 2018) and CPR Part 35, the expert must provide independent, objective evidence; they must not allow the instructing party's commercial interests to influence their opinion; and they must disclose all material information, including information adverse to the instructing party.
What should an expert report prepared by a QS expert typically contain?
Introduction and instructions received; description of documents reviewed; issues to be addressed (as defined by the instructing party or the tribunal); expert's analysis of each issue with evidence base; conclusions on each issue; any qualifications or assumptions; a statement that the report contains the expert's true and complete opinion; and the RICS Expert Witness PS compliance statement. The report should not contain legal submissions or advocacy — those are for the lawyers.
Can a QS act as both a party representative (quantum advocate) and an expert witness on the same matter?
No. These roles are mutually exclusive under RICS Expert Witness PS (2nd ed.). The party representative/quantum advocate acts in the client's interests; the expert witness has an overriding duty to the tribunal. A QS who acts as quantum advocate in preparing a claim cannot subsequently act as an independent expert witness on the same quantum issues. Attempting to combine the roles would be a breach of the RICS PS and would compromise the expert's credibility.
Section 6
Dispute & Claims Checklist
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Task
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Independence confirmed — no conflict of interest with either party
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Fee basis confirmed — no contingency arrangement
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Expert report structure follows RICS Expert Witness PS requirements
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All documents reviewed disclosed — including adverse documents
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Conclusions cross-referenced to supporting evidence
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Assumptions clearly identified with sensitivity analysis
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Statement of truth included — compliant with CPR Part 35 or applicable rules
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Expert discussions attended and joint statement produced
Section 7
CPD Learning Outcomes
- Prepare an expert witness report on quantum issues in compliance with RICS Expert Witness PS (2nd ed., effective 2 January 2018) and CPR Part 35 — maintaining independence, objectivity, and the overriding duty to the tribunal.
- Distinguish between the role of expert witness (duty to tribunal) and party representative/quantum advocate (duty to client), and ensure these roles are not conflated on the same matter.
- Participate in expert discussions, produce a joint statement of agreed and unagreed issues, and prepare for cross-examination while maintaining the expert's obligation of independence.
Section 8
Further Reading
- RICS Expert Witness PS, 2nd edition, effective 2 January 2018
- Civil Procedure Rules (CPR) — Part 35 (expert witnesses) and Practice Direction 35
- RICS, Conflict Avoidance and Dispute Resolution in Construction, 1st edition, April 2012 (reissued August 2024)
- RICS, Ascertaining Loss and Expense, 2nd edition, July 2024 — expert quantum methodology
- Technology and Construction Court Guide (TCC Guide) — expert evidence requirements
- Society of Construction Law — guidance on expert evidence in construction disputes
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