“to act fairly and impartially as between the parties, giving them a reasonable opportunity to present their cases and to deal with the cases of their opponents”
“When conducting arbitral proceedings, an arbitral tribunal is not bound by the rules of evidence and may receive any evidence that it considers relevant to the arbitral proceedings, but it must give the weight that it considers appropriate to the evidence adduced in the arbitral proceedings.”
“an arbitral tribunal may, when conducting arbitral proceedings, decide whether and to what extent it should itself take the initiative in ascertaining the facts and the law relevant to those arbitral proceedings.”
Rules of the High Court (Cap. 4A), Appendix D, Code of conduct for expert witnesses
RHC (Cap. 4A) App D · subsidiary legislation ·Source
“An expert witness is not an advocate for a party.”
“An expert witness shall exercise his independent, professional judgment in relation to such a conference and joint report, and shall not act on any instruction or request to withhold or avoid agreement.”
“A reference to an expert witness in this Part or Appendix D is a reference to an expert who has been instructed to give or prepare evidence for the purpose of proceedings in the Court.”
“The duty under paragraph (1) overrides any obligation to the person from whom the expert witness has received instructions or by whom he is paid.”
CIArb International Arbitration Practice Guideline: Party-appointed and Tribunal-appointed Expert Witnesses
Chartered Institute of Arbitrators, International Arbitration Practice Guideline: Party-appointed and Tribunal-appointed Expert Witnesses (2015) ·Source
CIArb Guidelines for Witness Conferencing in International Arbitration (with Explanatory Notes)
Chartered Institute of Arbitrators, Guidelines for Witness Conferencing in International Arbitration (April 2019) ·Source
Civil Justice Council, Guidance for the Instruction of Experts in Civil Claims (August 2014, amended December 2014)
CJC, Guidance for the Instruction of Experts in Civil Claims (2014) ·Source
9-15 General duties: overriding duty; independence test (same opinion whoever instructs); confine to expertise; consider all material facts; tell instructing party of change of opinion.
16-17 Before appointment check expertise, familiarity with duties, time and cost, availability, and no potential conflict of interest; agree terms of appointment.
27 Expert whose instructions are incompatible with duties may consider withdrawing, after discussion and considering a request for directions.
64-66 Amending reports: no amendment that distorts true opinion; change of opinion after meeting needs signed note; significant change needs amended report with reasons.
77-82 Must not instruct experts to avoid or defer agreement; joint statement should say so expressly; agreements not binding unless parties agree, but refusal may count on costs.
88-91 Contingency fees strongly discouraged; sanctions include costs, inadmissibility, professional discipline.
Civil Procedure Rules, Part 35 (Experts and Assessors)
35.1 Expert evidence restricted to what is reasonably required (Philip slide 10 'NB').
35.3 Overriding duty to help the court; overrides any obligation to the instructing or paying party.
35.4(1) Court's permission needed (Philip slide 6 'Must have the court's permission').
35.10(3)-(4) Report must state the substance of all material instructions; instructions not privileged, but disclosure/questioning only if reasonable grounds to think the statement inaccurate or incomplete.
35.12(3)-(5) Court may direct discussion and a joint statement; content of discussion not referred to at trial unless parties agree; agreement does not bind parties unless they expressly agree.
“Where experts reach agreement on an issue during their discussions, the agreement shall not bind the parties unless the parties expressly agree to be bound by the agreement.”
Federal Court of Australia, Use of Generative Artificial Intelligence Practice Note (GPN-AI)
Federal Court of Australia, Use of Generative Artificial Intelligence Practice Note (GPN-AI) (16 April 2026) ·Source
Guidelines on the Use of Generative Artificial Intelligence for Judges and Judicial Officers and Support Staff of the Hong Kong Judiciary
Hong Kong Judiciary, Guidelines on the Use of Generative Artificial Intelligence for Judges and Judicial Officers and Support Staff of the Hong Kong Judiciary (July 2024) ·Source
HKIAC, Guide to Arbitration under the Domestic Arbitration Rules 2014
HKIAC Guide to Arbitration under the Domestic Arbitration Rules (2014) · institutional guidance ·Source
“The arbitral tribunal may determine the manner in which a witness or expert is examined.”
“After consulting with the parties, the arbitral tribunal shall establish terms of reference for the expert, and shall communicate a copy of the expert's terms of reference to the parties and HKIAC.”
High Court Practice Direction HC 142: responsible use of generative AI in court documents
High Court of Ireland, Practice Direction HC 142 (29 July 2026; in operation 1 September 2026) ·Source
“Generative Artificial Intelligence has not been used for the purposes of generating the substantive content of this report which reflects my own opinions, knowledge and evidence.”
“the expert must disclose the nature and extent of that use to the extent necessary to enable the Court and the parties properly to assess the reliability, independence and evidential weight of the opinion expressed”
RICS professional standard: Surveyors acting as expert witnesses (Global, 5th edition)
RICS, Surveyors acting as expert witnesses (professional standard, Global 5th edition, July 2026; effective 30 November 2026) ·Source
“be entirely their own work except where some work is carried out at their direction and under supervision (including material generated through artificial intelligence), in which case the member's evidence must make it clear which items of work have been carried out this way”
14.2 Permission always required; scope limited to what is necessary; costs estimates and issue-limited permission (CPR 35.4).
14.5 Meetings of experts: purposes listed; lawyers must not attend save exceptionally with permission and must not dictate what experts say; meet before and after reports.
14.6 Joint statement is 'a critical document'; experts may share drafts with lawyers for information only; lawyers must not negotiate, draft or revise it; serious concerns go first to the other side's lawyers, then to the court.
14.7 Reports independent and unbiased; parties identify issues, expert decides content; spreadsheets disclosed in native format; primary-fact evidence from an expert goes in a factual witness statement.
14.8 Presentation: summary at start of evidence, sequencing options, concurrent evidence ('hot-tubbing'), pre-trial tutorial.
1.6 Use of AI by legal representatives: personal responsibility; doubt about disclosure resolved in favour of disclosure; verify AI-assisted research and citations.
“The legal advisers must not engage in negotiating, drafting, or revising the experts' joint statement either directly or through seeking to influence their expert as to the contents of the statement.”
[2022] EWHC 479 (QB) · QB (Senior Master) · Senior Master Fontaine · 7 March 2022 ·Find Case Law
[9]-[12] Claimants' dust expert sent successive drafts of the joint statement to his instructing solicitors, who commented on substance (at least 16 substantive comments) without the other side's knowledge; claimants conceded serious transgression.
[31] Expert's approach showed he saw himself as an advocate.
[34]-[35] Permission revoked though over £255,000 spent and 159 households affected; new expert allowed as no trial date was fixed.
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
BDW Trading Ltd v Integral Geotechnique (Wales) Ltd
[2018] EWHC 1915 (TCC) · TCC · HHJ Stephen Davies (sitting as a High Court judge) · 25 July 2018 ·Find Case Law
[15] Expert should have declared that he and his firm regularly worked for the party calling him (no actual conflict found).
[16]-[18] Expert sent draft joint statement to his solicitors and changed it after feedback: a serious transgression; expert may show the draft to solicitors, but should not ask for comments and solicitors should not give them, save openly to both experts where a material misunderstanding of law or fact may mislead the court.
[19]-[20] No sanction: expert genuinely unaware and substance not materially changed.
“That however will be done in the open so that everyone, including the trial judge if the case proceeds to trial, can see what has happened”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2025] EWHC 1451 (Ch) · ChD (Patents Court) · Bacon J · 16 June 2025 ·Find Case Law
[44]-[47] 33 economic and valuation expert reports and letters by the close of evidence, many during trial; impossible to digest.
[48] Experts should adjust to emerging evidence (citing Royal Mail Group v DAF Trucks [2024] EWCA Civ 181 [177], not read by me), but abandoning a position that was untenable from the outset suggests it was influenced by the desire to advance the client's case (PD 35 para 2.1).
[49]-[50] Expert evidence is not a negotiation from polarised positions; start objective and defensible; resolve differences at the joint meeting and reflect them in the joint statement.
“expert evidence at a trial is not and cannot be seen as a negotiation process, where the experts start from extremely polarised and partisan positions, only to edge incrementally towards the centre ground as the trial progresses.”
“The proper course is for each opposing expert to start from a position that is objective and defensible.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Chevalier (Construction) Co Ltd v Tak Cheong Engineering Development Ltd
[2011] HKCFI 139 · Court of First Instance, Hong Kong · Lam J (M H Lam J) · 23 February 2011 ·Source
“It is not good enough for an expert to state in a joint report that he disagrees with the other expert. He should explain intelligibly why he disagrees.”
[2024] HKCFI 3366 · Court of First Instance, Hong Kong (Construction and Arbitration Proceedings) · Mimmie Chan J · 22 November 2024 ·Source
“an arbitrator is entitled to accept the valuation of one expert over another's, and doing so is neither "plainly wrong" nor "open to serious doubt".”
“This naturally extends to where the arbitrator decides to accept one part of an expert's valuation, and another part of another expert's valuation, on the basis of the arbitrator's own expertise.”
[2021] EWHC 1413 (TCC) · TCC · Joanna Smith J · 26 May 2021 ·Find Case Law
[61]-[64] Defendant breached PTR order conditions (disclose all material supplied to experts, site-visit documents, sources of data); permission to rely on its three technical experts refused mid-trial.
[72]-[84] Breaches of CPR 35, PD 35 and the 2014 Guidance: unrecorded direct contact between client's in-house specialists and experts; client contact during joint statement period (TCC Guide then 13.6.3 applies equally to parties); unilateral site visits; opinions directly influenced by the client.
[87] Those breaches alone would justify refusing permission.
[93]-[94] Lawyers must oversee foreign experts unfamiliar with English rules; permission presupposes compliance; level playing field.
“the use of experts only works when everyone plays by the same rules.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Glover v Fluid Structural Engineers & Technical Designers Ltd
[2024] EWHC 1257 (TCC) · TCC · Simon Lofthouse KC (sitting as a Deputy High Court Judge) · 23 May 2024 ·Find Case Law
[14]-[29] Opposing expert noticed changes in the claimants' expert's draft joint statement that read like lawyers' work; claimants' solicitors had tracked changes to drafts and stripped the metadata; they later admitted non-compliance.
[43] Court could not be satisfied of the expert's independence in the joint statement process.
[70]-[74] Permission for the original expert revoked (by agreement); replacement expert allowed on conditions because the trial date could be kept and the claimants' case depended on engineering evidence.
“substantial and impermissible interference in the expert statement process by those acting for the claimants.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Pacific China Holdings Ltd (in liquidation) v Grand Pacific Holdings Ltd
[2013] HKCFA 13 · Court of Final Appeal, Hong Kong (Appeal Committee) · Ma CJ, Chan PJ and Ribeiro PJ · 21 February 2013 ·Source
Griffiths v TUI UK Ltd
[2023] UKSC 48 · UKSC · Lord Hodge (Lord Lloyd-Jones, Lord Briggs, Lord Burrows and Lord Stephens agreeing) · 29 November 2023 ·Find Case Law
[36] Role of the expert: assist on specialised matters outside the judge's expertise; must not usurp the judge's functions as ultimate decision-maker.
[37]-[39] Quality of reasoning is of prime importance; an expert report should set out its reasoning (PD 35 para 3.2(9) and CJC Guidance para 62).
[61]-[68] Rule may not apply where: collateral matter; manifestly incredible fact evidence; bare ipse dixit; obvious mistake on the face of the report; facts contrary to the report's basis; expert already had sufficient opportunity to respond (e.g. CPR 35.6 questions); possibly PD 35 non-compliance (seek directions).
[70] Rule in Browne v Dunn applies to expert witnesses: a party must challenge by cross-examination evidence it wants rejected on a material point; purpose is fairness of the trial, including to the expert; not rigid.
[75]-[78] Uncontroverted report could not fairly be attacked in closing; Mr Griffiths did not have a fair trial; on the uncontroverted evidence he proved causation.
“the role of an expert is to assist the court in relation to matters of scientific, technical or other specialised knowledge which are outside the judge's expertise by giving evidence of fact or opinion; but the expert must not usurp the functions of the judge as the ultimate decision-maker on matters that are central to the outcome of the case.”
“If the reasons stand up the opinion does, if not, not.”
“both courts and arbitrators in this country operate on an adversarial system of achieving justice”
“That rule extends to both witnesses as to fact and expert witnesses.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2012] EWCA Civ 392 · EWCA · Lewison LJ (Elias LJ and Ward LJ agreeing) · 14 March 2012 ·Find Case Law
[17] Approves Stallwood [17]; overriding duty applies to the joint statement; if the expert can no longer support the case he must say so; courts discourage expert shopping; a change of view is not enough to justify a new expert; points from a new expert can still be put in cross-examination.
[21]-[27] District judge entitled to refuse a change of expert after an adverse joint statement; appeal allowed.
“If at any time the expert can no longer support the case of the person who instructed him, it is his duty to say so.”
“if an expert changes his mind about the merits of a claim, the sooner he says so the better.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Hebei Import & Export Corporation v Polytek Engineering Co Ltd
[1999] HKCFA 40 · Court of Final Appeal, Hong Kong · Li CJ, Litton PJ, Ching PJ, Bokhary PJ, Sir Anthony Mason NPJ (unanimous; leading judgment Sir Anthony Mason NPJ) · 9 February 1999 ·Source
“a party to an arbitration who wishes to rely on a non-compliance with the rules governing an arbitration shall do so promptly and shall not proceed with the arbitration as if there had been no non-compliance, keeping the point up his sleeve for later use after an award is made”
“The respondent was given a copy of the experts' report and an opportunity to deal with it.”
Imperial Chemical Industries Ltd v Merit Merrell Technology Ltd
[2018] EWHC 1577 (TCC) · TCC · Fraser J · 21 June 2018 ·Find Case Law
[184]-[187] Quantum expert decided for himself a contract interpretation (actual cost not schedule of rates) and argued it: not acceptable for an independent expert.
[197]-[199] Expert took and created positions on disputed facts in his client's favour; evidence prepared without sufficient attention to the duty to the court.
[233]-[236] All of one party's experts found lacking in independence; 'remarkable' if coincidence.
[237] Six practical rules applying the Ikarian Reefer: same material for like experts; no choosing between versions of fact; no partisan stance on interlocutory applications; joint process constructive and proportionate; notice of late analysis, no surprise reports during trial; no loosening of the principles. Lawyers must explain the principles.
“Experts of like discipline should have access to the same material.”
“it is not the place of an independent expert to identify which version of the facts they prefer. That is a matter for the court.”
“There are some jurisdictions where partisan expert evidence is the norm. For the avoidance of any doubt, this jurisdiction is not one of them.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2011] UKSC 13 · UKSC · Lord Phillips (Lord Brown, Lord Collins, Lord Kerr and Lord Dyson agreeing; Lord Hope and Lady Hale dissenting) · 30 March 2011 ·Find Case Law
[1]-[8] Expert psychologist signed a joint statement drafted by the other side's expert that did not reflect her views; client sued in negligence.
[49]-[50] No conflict between duty to client and duty to court: the expert contracts to perform the CPR duties; the expert must give evidence honestly even if it involves concessions against the client.
[62] Immunity from suit for breach of duty in relation to participation in legal proceedings abolished (absolute privilege in defamation kept).
[123] Lord Dyson: immunity did not stop the pre-Woolf 'hired gun'.
“Thus there is no conflict between the duty that the expert owes to his client and the duty that he owes to the court.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2016] UKSC 6 · UKSC · Lord Reed and Lord Hodge (Lady Hale, Lord Wilson and Lord Toulson agreeing) · 10 February 2016 ·Find Case Law
[38] Four matters: admissibility; legal team's responsibility to keep expert to role; court's policing of duties; economy.
[44] Four considerations governing admissibility of skilled evidence: assistance; knowledge and experience; impartiality; reliable body of knowledge.
[48] Expert must explain the basis of evidence; bare ipse dixit is worthless; what carries weight is the reasoning.
[49] Expert must not supplant the court as decision-maker; may sometimes address the ultimate issue.
[51] Independence and impartiality go to admissibility, not merely weight (citing Toth v Jarman [100]-[102]).
[52]-[53] Quotes Cresswell J's Ikarian Reefer list (pp 81-82) omitting case citations; adopted for Scotland.
[57] Counsel and solicitors must check expertise and admissibility, make sure expert knows the duties, and disclose relevant material including material pointing the other way.
“(i) whether the proposed skilled evidence will assist the court in its task; (ii) whether the witness has the necessary knowledge and experience; (iii) whether the witness is impartial in his or her presentation and assessment of the evidence; and (iv) whether there is a reliable body of knowledge or experience to underpin the expert's evidence.”
“what carries weight is the reasoning, not the conclusion.”
“The fact-finding judge cannot delegate the decision-making role to the expert.”
“An expert witness in the High Court should never assume the role of an advocate.”
“That should include not only material which supports their client's case but also material, of which they are aware, that points in the other direction”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Kohls v Ellison, No 24-cv-3754 (LMP/DLM) (D Minn, 10 January 2025), ECF No 46 (Provinzino J) · 10 January 2025 ·Source
“But when attorneys and experts abdicate their independent judgment and critical thinking skills in favor of ready-made, AI-generated answers, the quality of our legal profession and the Court's decisional process suffer.”
“now require attorneys to ask their witnesses whether they have used AI in drafting their declarations and what they have done to verify any AI-generated content.”
[2023] EWHC 2620 (TCC) · TCC · Eyre J · 1 November 2023 ·Find Case Law
[69] Experts who revised their opinions after a judgment in related proceedings were not thereby partisan; an expert may revise an opinion in light of a judicial finding or points in cross-examination and would be failing in duty not to reflect.
[70] An earlier different opinion may still be relevant to weight.
“Indeed an expert witness would not be fulfilling his or her duty to the court if he or she failed to reflect on such points and on the earlier judgment.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
LR v Secretary of State for the Home Department (LR (Male VOTs) Albania CG)
[2026] UKUT 315 (IAC) · Upper Tribunal (Immigration and Asylum Chamber) · Deputy Chamber President Plimmer, UTJ Blundell and UTJ Landes · 13 August 2026 ·Find Case Law
“We do not consider there to have been any proper foundation for such a serious allegation.”
“None of those points begins to found a suggestion that the Professor used AI to write his report.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2019] EWCA Civ 392 · EWCA · Sir Terence Etherton MR, Hamblen LJ and Holroyde LJ (judgment of the court) · 19 March 2019 ·Find Case Law
[59]-[61] A false statement verified by a statement of truth (including by a reckless expert) will usually merit committal to prison; reckless expert almost as culpable as a deliberate liar.
[75] Six months suspended held unduly lenient, but not increased because the guidance was new.
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Marples v Secretary of State for Education
[2025] EWHC 2794 (Ch) · ChD (BPC) · Rajah J · 28 October 2025 ·Find Case Law
[26]-[28] Principles: permission presupposes compliance; joint statement prepared for the court; parties and solicitors not to be involved in negotiating or drafting it (citing Dana [77], BDW [18]); revocation of permission is an available sanction.
[30]-[43] Claimant (a trained accountant) secretly rewrote his forensic accountant's contributions to the joint statement (about 150 amendments) and asked for his contribution to be deleted from the track changes; expert also had undisclosed prior business links with the claimant.
[44]-[46] Deliberate, cynical, planned breach; report and joint statement not independent; permission refused.
[47] Third judicial criticism of the same expert.
“Where a joint statement is prepared pursuant to CPR 35.12 it is prepared for the benefit of the Court, not as a means of advancing the case of one or other party”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2005] HKCFA 54 · Court of Final Appeal, Hong Kong · Chan PJ (Ribeiro PJ, Litton NPJ, Sir Noel Power NPJ, Lord Scott of Foscote NPJ) · 16 September 2005 ·Source
“The acceptability of an expert's opinion depends very much on how sound and convincing the reasons for his opinion are.”
[1993] HKCU 613 (MP No 2219 of 1992) · High Court of Hong Kong (in Chambers) · Kaplan J · 15 January 1993 ·Source
Presbar Diecastings Ltd v G W Atkins & Sons Ltd
[2026] EWHC 399 (Ch) · ChD (BPC, Manchester) · HHJ Stephen Davies (sitting as a High Court judge) · 25 February 2026 ·Find Case Law
[62]-[64] Industry experts with no prior court experience were helpful, but one trespassed into decision-making and strayed beyond the permission granted.
[66]-[71] Accountancy expert given narrow instructions was not obliged to refuse them or to go beyond them, being transparent about them; only in extreme cases must an expert refuse instructions requiring assumptions plainly untrue or inappropriate; his joint-statement criticisms of matters he had not reported on carried less weight.
“There may be some extreme cases where an expert is bound to refuse instructions where, for example, they require the expert to assume certain facts or certain propositions which are plainly untrue or inappropriate.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2021] HKCA 1229 · Court of Appeal, Hong Kong · G Lam JA and Chow JA · 19 August 2021 ·Source
“The connections that an expert has with a party and the apparent interest he has in the outcome, even if insufficient to preclude him from giving evidence, are relevant factors that may affect the weight to be placed on his evidence.”
“Single joint expert evidence is preferred and has been used as the starting point for expert directions by the Construction Court.”
[2021] EWCA Civ 6 · EWCA · Coulson LJ, Males LJ and Carr LJ (each gave reasons) · 11 January 2021 ·Find Case Law
[2], [6]-[16] Facts: delay expert retained (Singapore entity) for the employer in one ICC arbitration on a petrochemical project; another group entity then engaged against the employer's project manager in a second arbitration on the same project; conflict check had been run group-wide; injunction granted by O'Farrell J, appeal dismissed.
[59]-[67] Coulson LJ: the overriding duty to the tribunal does not prevent a duty of loyalty, but no need to find a freestanding fiduciary duty; depending on the retainer, the relationship may have one fiduciary characteristic, a duty to avoid conflicts.
[69]-[81] Express no-conflict term in the retainer was a contractual duty; on its construction it bound the whole group, given the group-wide conflict check and one-firm marketing.
[82]-[98] Clear conflict: overlap of parties, role, project and subject matter; delay experts typically give wide-ranging support, not just testimony; the same expert can act for and against the same client on different matters; conflict is a matter of degree.
[101], [123] Groups can limit conflict representations to the instructed entity if they wish.
[104]-[113] (Males LJ) Save in remote cases an expert is not a fiduciary; relationship is contractual; the CPR do not apply in arbitration but international practice (IBA Rules, CIArb Protocol) also requires independence; independence is owed to the client too; the professional expert is part of the litigation team.
[125] (Carr LJ) No conflict between loyalty and the duty of independence.
“But a conflict of interest is a matter of degree.”
“Save perhaps in circumstances far removed from the present case, an expert witness is not a fiduciary and does not owe fiduciary duties to his client.”
“the relationship between the expert and his client is essentially contractual.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2006] EWHC 2600 (QB) · QB · Teare J · 25 October 2006 ·Find Case Law
[17] Experts' discussion contemplates changes of opinion; a change alone is no reason to allow a disappointed party a new expert.
[18]-[19] Agreement between experts does not bind the parties (CPR 35.12(5)); a change of opinion cannot bind the instructing party; a further expert is not ruled out but will rarely be appropriate.
[21] Test: good reason to suppose the expert agreed or modified his opinion for reasons that cannot properly or fairly support it (e.g. stepped outside expertise or brief, or incompetence); then whether further evidence is reasonably required.
“It is likely that it will be a rare case in which such good reason can be shown.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Tata Consultancy Services Ltd v Disclosure and Barring Service
[2024] EWHC 1185 (TCC) · TCC · Constable J · 17 May 2024 ·Find Case Law
[478]-[479] Quantum expert's assessment covered a different period and a fundamentally different claim from the pleaded one: the expert advancing a new case, which is not his role.
“This is not the role of an expert.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer)
[1993] 2 Lloyd's Rep 68 (Comm Ct), 81-82; CA [1995] 1 Lloyd's Rep 455 · QBD (Commercial Court); CA · Cresswell J; CA (judgment of the court) · 1993-02-25; CA 1994-12-08 ·Source
pp 81-82 Seven duties: independent product uninfluenced by litigation; objective unbiased assistance, never an advocate; state facts and assumptions, consider facts that detract; say when outside expertise; flag insufficient data and provisional opinions; communicate change of view after exchange; provide underlying documents with the report.
Toth v Jarman
[2006] EWCA Civ 1028 · EWCA · Sir Mark Potter P, Arden LJ and Wall LJ (judgment of the court) · 19 July 2006 ·Find Case Law
[100]-[102] A conflict does not automatically disqualify; the key question is independence; a material or significant conflict will likely lead the court to decline to act on, or admit, the evidence; disclose early.
[108], [111]-[113] Conflicts not obviously immaterial must be disclosed, at latest with the report (earlier if permission for a named expert is sought); it is for the court, not the parties, to decide materiality; parties cannot agree to keep it from the court.
[114], [119]-[120] Expert's CV should disclose possible conflicts; recommended declaration of no undisclosed conflict and duty to update.
“it is for the court and not the parties to decide whether a conflict of interest is material or not.”
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
[2026] HKCFI 1530 · Court of First Instance, Hong Kong · Mimmie Chan J · 16 March 2026 ·Source
“it was open to M to apply for such appointment if it considered that it was necessary to do so, instead of waiting for the Tribunal to order the appointment on its own accord.”
[2024] EWHC 667 (TCC) · TCC · Jefford J · 25 March 2024 ·Find Case Law
[57] QS expert without RICS membership still qualified by experience to give the costs evidence.
[58] But he strayed outside his expertise into causation of defects (no weight); accepted he was instructed not to sign the second joint statement, contrary to his duty to the court; relied in the witness box on a pricing exercise not in his reports.
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Protocols and guidance
CIArb Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration
Chartered Institute of Arbitrators, Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration (September 2007), as reproduced in Annex I to the CIArb International Arbitration Practice Guideline: Party-appointed and Tribunal-appointed Expert Witnesses (2015) ·Source
“4.1 An expert's opinion shall be impartial and objective.”
“the Arbitral Tribunal shall disregard the expert's written opinion and testimony either in whole or in part, as it considers appropriate in all the circumstances.”
“I confirm that I have referred to all matters which I regard as relevant to the opinions I have expressed and have drawn to the attention of the arbitral tribunal all matters, of which I am aware, which might adversely affect my opinion.”
Report on Party-Appointed Expert Witnesses in International Arbitration: Effectiveness and Best Practice
Chartered Institute of Arbitrators, Report on Party-Appointed Expert Witnesses in International Arbitration: Effectiveness and Best Practice (V1, July 2026; published 9 July 2026) ·Source
“the findings presented in the Report reflect perceptions, experiences and professional judgments of respondents, rather than independently verified empirical measurements of practice.”
“engaging expert witnesses only at the evidentiary hearing stage is inadequate.”
“71% of all respondents favouring appointment during the pre-arbitration stage.”
“a divergence that represents one of the starkest role-based splits in the entire data set.”
“5.1.1 Over-instruction occurs when the instructions given to an expert witness improperly shape, constrain, or direct the expert witness's opinions in a way that compromises, or appears to compromise, the expert witness's independence and objectivity.”
“In-house counsel reported the highest perceived incidence of overinstruction”
“A decisive majority of 73% said that they are "never" or "not often" over-instructed.”
“an underestimation of the subtle procedural and strategic pressures”
“requiring expert witnesses to identify and explain any assumptions provided by counsel along with their reasoning; to declare expressly whether any instruction was declined or reformulated; and to present alternative analyses where an instruction appears unrealistic”
“Counsel shall have no involvement in the drafting, negotiation or substantive content of any joint expert witness report.”
“Expert witnesses are therefore seen primarily as report writers, rather than as early strategic advisors who can shape issues, test claims, and identify technical weaknesses”
“However, such short term cost savings can prove counterproductive because late instructions compress the time available to produce more robust reports and increase the intensity of the expert witnesses' analysis, ultimately raising overall costs.”
“77% of arbitrators, 44% of expert witnesses, 66% of external counsel, and 80% of in-house counsel consider that the parties and/or tribunals give expert witnesses enough time to carry out their work”
“81% of arbitrators, 81% of expert witnesses, 90% of external counsel, and 83% of in-house counsel agree that the tribunal should require the expert witnesses to meet at an early stage”
Civil Justice Council, Use of AI for Preparing Court Documents: Interim Report and Consultation
Civil Justice Council, Use of AI for Preparing Court Documents: Interim Report and Consultation (February 2026) ·Source
“We propose a requirement that the expert explains what use of AI has been made other than for transcription (or other administrative uses) and that the expert identifies the AI tools used.”
Katherine Bell, 'Expert evidence in construction disputes: arbitrator perspective', GAR Guide to Construction Arbitration (6th edn)
K Bell, 'Expert evidence in construction disputes: arbitrator perspective' in The Guide to Construction Arbitration (6th edn, Global Arbitration Review, 12 August 2025) ·Source
“the appointment of an expert by the tribunal does not necessarily result in considerably fewer expenses for the parties”
Commentary on the revised text of the 2020 IBA Rules on the Taking of Evidence in International Arbitration
IBA Task Force, Commentary on the revised text of the 2020 IBA Rules on the Taking of Evidence in International Arbitration (January 2021) ·Source
“Where the experts succeed in reaching agreement on their findings, the parties and the arbitral tribunal will likely accept those findings, so that the hearing may focus on the truly disputed aspects of the case.”