Working with expert witnesses... is a new monthly article series. The series takes a look at the role of expert witnesses in a range of sectors from the perspective of the legal and other professionals who work with them. If you are interested in being featured in the series, you can contact us at policy@ewi.org.uk.
In the third article in the series, Sean Gates from Gates Aviation, discusses his experience of working with expert witnesses in the aviation sector.
Introduction
Over a lifetime of litigation, I have, as a lawyer, had multiple experiences with experts, some positive and at least one in particular negative. On the positive side, brilliant, focused and charismatic experts were core to success in cases involving the criminal prosecution of a pilot following a major accident. The prosecution tendered no expert evidence after the expert I had appointed convincingly demonstrated to the judge, through skill and charm, the weaknesses in the prosecution's case. The case was heard in the local Portuguese criminal court, and the highly experienced French pilot persuasively supported the case for the defence. The presence of the same expert persuaded the lawyers defending my clients' civil claim to settle when it became apparent that his evidence would likely destroy their contention that the accident was caused by pilot error. In another case, my expert in a claim involving the destruction by fire of an aircraft parked at a private airfield was convincing in his evidence, but the arbitrator dismissed it for what I remain convinced were manifestly inadequate reasons, indicating in his decision that he disliked the somewhat pedagogic manner in which our expert gave his evidence, and substituted his own opinion of the cause of the fire which destroyed the insured aircraft. I stress that I have endeavoured to eliminate sour grapes from my narrative and mention this as a case in which, nowadays, I might have sought resolution by the agreed appointment of an expert acting on his own rather than in the form of an agreed arbitration. These were both cases in which I learned to take the expert’s personality as well as their expertise into account when choosing an expert witness. Recent decisions in aviation, as well as in other areas of law, have highlighted changes in the use of experts across multiple jurisdictions, which merit attention and consideration. In the interests of full disclosure, I must mention that I have stepped back from personally leading litigation and have established an organisation focussing on the identification and provision of experts in various aspects of aviation litigation.
Expert evidence in modern dispute resolution
Expert evidence occupies a central role in modern dispute resolution. Courts, arbitral tribunals, and parties themselves are increasingly relying on experts to clarify technical issues that exceed the knowledge of judges or advocates. Whether the dispute concerns aviation safety, financial risk, or the interpretation of contractual mechanisms, the expert can provide both factual illumination and analytical frameworks. However, the weight and admissibility of expert evidence vary depending on its quality, impartiality, and relevance. Courts have consistently warned against the dangers of partisan or outdated expertise, while simultaneously affirming the indispensable role of experts when properly selected.
Recent jurisprudence highlights two key themes: first, that expert evidence must meet stringent admissibility requirements; and second, that expert determination, as a dispute resolution mechanism, offers distinct advantages but also limitations when compared to litigation and arbitration. The following discussion examines both points, drawing on recent decisions from Canada and the United Kingdom.
Admissibility of expert evidence
In R v Mohan, the Supreme Court of Canada articulated four threshold requirements for the admission of expert evidence: logical relevance, necessity in assisting the trier of fact, absence of an exclusionary rule, and the presence of a properly qualified expert willing and able to provide impartial, independent, and unbiased evidence.¹ These requirements were affirmed and refined in White Burgess Langille Inman v Abbott and Haliburton Co, where the Court emphasised that the judge must act as gatekeeper, balancing the benefits of admitting expert testimony against the risks of confusion, delay, or undue prejudice.² The Ontario Court of Appeal later confirmed this two-stage analysis in R v Abbey.³
Judges have repeatedly stressed the risks associated with expert evidence. In O’Brien v Maxar Technologies Inc, Justice Akbarali cited White Burgess in underscoring that experts may lead the trier of fact to defer uncritically to their views, rely on unproven material not subject to cross-examination, or cause an inordinate expenditure of time and money.⁴ These concerns place a heavy burden on parties to ensure that only appropriately qualified and current experts are retained.
The Ontario Court of Appeal’s decision in S and others v Ukraine International Airlines concerned the tragic downing of Flight PS752 over Tehran on 8 January 2020. The Court upheld the trial judge’s finding that Ukraine International Airlines (UIA) was negligent in permitting the flight to depart, thereby incurring unlimited liability under the 1999 Montreal Convention for the deaths of 176 people on board.⁵
Central to the outcome was the role of expert evidence. Mr E was qualified at trial by the Judge on aviation security threats and risk assessments, and Captain G was qualified in aviation safety management systems and the conduct of safety risk assessments. Both provided testimony of such clarity and independence that the Court cited their analyses substantively in its judgment, finding that UIA had breached its duty of care.
By contrast, the defendant airline’s lawyers relied on an expert, whom the trial judge found, upon applying the Mohan test, had outdated expertise, particularly as he lacked experience with the International Civil Aviation Organisation’s document 10084 which is a key standard developed after the downing of Malaysia Airlines Flight MH17 in 2014.⁶ The Court also noted that his mischaracterisation of opposing experts’ testimony, failure to acknowledge errors, and selective omission of evidence indicated advocacy rather than impartial assistance.⁷ Consequently, his evidence failed both the qualification and gatekeeping stages of admissibility.
This decision highlights two critical lessons. First, the credibility and currency of an expert are decisive. Second, an expert's ability to provide impartial, unbiased assistance rather than partisan advocacy will affect judicial reliance. In complex technical disputes, such as aviation negligence cases, the integrity of expert evidence can determine the outcome of the case.
Expert determination and arbitration
A different aspect of the utility of experts arises in Dandara South East Ltd v Medway Preservation Ltd & another, where the High Court considered the effect of an expert determination clause within a land development agreement.⁸ The key question was whether such a clause could be separable from the underlying contract in the same way as an arbitration clause, thereby surviving termination of the main agreement.
The contract contained an expansive dispute resolution provision (clause 28), stipulating that any dispute under or in connection with the contract was to be referred to expert determination. The defendants argued that this required all disputes, including whether the contract had been validly terminated, to be resolved by an expert, and sought a stay of court proceedings. The Court held that clause 28 was indeed an all-embracing provision, mirroring the breadth of disputes typically subject to arbitration clauses. Drawing an analogy with section 7 of the Arbitration Act 1996, which establishes the separability of arbitration clauses, ⁹ the Court concluded that there was no reason in principle why an expert determination clause could not also be separable. While unusual in scope, the provision created what the House of Lords in Fiona Trust v Privalov described as a “one-stop” mechanism for dispute resolution.¹⁰Importantly, the Court rejected the claimant’s argument that expert determination was unsuitable for disputes concerning termination and breach, holding that the parties’ objective intention was for such disputes to fall within clause 28. Accordingly, proceedings were stayed in favour of expert determination. This case illustrates the courts’ willingness to construe expert determination clauses broadly, recognising their potential to provide finality and efficiency in commercial contracts. It also establishes, for the first time, that such clauses may be separable, which is a development of significant importance for commercial drafting. I am bound to say that in my experience, much cost could have been avoided in aviation cases by the use of experts in a determinative role, given that in this area, as with many others, the need arises at considerable expense to educate the lawyers and the judge, where expert support is limited to giving evidence. Of course, I have to accept that that might have run counter to the interests of my own firm had the practice existed at that time!
In WH Holdings Ltd v E20 Stadium LLP, the High Court considered whether an expert determination under a concession agreement relating to the Queen Elizabeth Park Stadium could be set aside for manifest error.¹¹ The agreement provided that disputes concerning gain-sharing provisions would be referred to expert determination, with the expert’s decision binding absent manifest error. The dispute arose when certain West Ham United Football Club shareholders entered into a put-and-call option arrangement. E20 argued that this triggered the gain-sharing clause, and the appointed expert agreed, ordering WH Holdings to pay £3.6 million. WH Holdings challenged the decision, alleging manifest error.
The Court reaffirmed that parties who agree to be bound by expert determination will generally be held to their bargain, absent fraud, bad faith, or the expert exceeding their mandate. The doctrine of manifest error provides a narrow escape, typically limited to obvious and indisputable mistakes. The Court drew on Veba Oil Supply & Trading GmbH v Petrotrade Inc, which defined manifest error as an oversight “so obvious and obviously capable of affecting the determination as to admit no difference of opinion.”¹² In this case, the Court found that the expert had misapplied defined contractual terms, conflating “or” with “and” and erroneously blending multiple transactions. This produced a calculation that lacked a basis in the contract. The Court concluded that the mistake was indeed manifest and therefore set aside the determination. The decision is significant because challenges to expert determinations rarely succeed. It underscores that while expert determination offers finality, it is not immune to correction where the error is plain and fundamental. At the same time, it confirms the limited scope of judicial review: the court does not rehear the merits. It intervenes only in cases of manifest error, fraud, or excess of jurisdiction.
These cases illustrate the diverse roles experts play in dispute resolution. A key distinction lies between the use of expert evidence in litigation or arbitration and the use of expert determination as a contractual dispute resolution mechanism. In litigation and arbitration, experts provide evidence to assist the tribunal in reaching its own decision. Their role is advisory, and their influence depends on the court’s assessment of admissibility, impartiality, and reliability. The ultimate decision-making power rests with the judge or arbitrator. This ensures judicial oversight but may prolong proceedings, as competing experts must be cross-examined and their methodologies comprehended and scrutinised.¹³
By contrast, in expert determination, the expert acts not as a witness but as the decision-maker. The parties effectively contract out of adjudication by courts or tribunals, appointing a technical specialist whose determination is binding (subject to fraud, excess of jurisdiction, or manifest error).¹⁴ This offers speed, cost-effectiveness, and subject-matter expertise but carries risks: the absence of appeal or extensive review means that an erroneous decision may stand unless it amounts to manifest error. As WH Holdings v E20 demonstrates, judicial intervention is rare and limited.¹⁵
Arbitration occupies an intermediate position. Like litigation, arbitrators adjudicate disputes and weigh expert testimony. Unlike litigation, arbitration affords greater flexibility in procedure and confidentiality. Importantly, arbitration clauses benefit from statutory separability under section 7 of the Arbitration Act 1996.¹⁶ Following Dandara, it appears that expert determination clauses may also enjoy separability where broadly drafted, thereby enhancing their resilience against termination challenges.¹⁷
Conclusion
The comparative utility of each mechanism may be summarised as follows:
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Litigation ensures oversight and precedent but may be costly, adversarial, and slow.
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Arbitration combines adjudication with procedural flexibility and international enforceability but still entails significant costs.
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Expert determination offers speed, expertise, and finality, but it sacrifices appellate review and may be unsuitable for disputes that require in-depth legal analysis.
Parties drafting dispute resolution clauses must therefore weigh these trade-offs. Where commercial certainty, cost saving, speed and technical accuracy are paramount, expert determination may be a viable option. Where broader issues of law, fairness, or multi-jurisdictional enforcement arise, arbitration or litigation may be preferable, whilst bearing in mind the vicissitudes of judges and arbitrators and the opportunities for appeal and delay, which can incentivise the party in the right to settle contrary to the justice of the case and potentially to the benefit of the party with the deepest pockets.
The utility of experts in dispute resolution is multifaceted. In litigation and arbitration, experts are essential for illuminating complex issues but must satisfy strict admissibility standards, as the S v UIA decision demonstrates. Within contractual frameworks, expert determination clauses can provide finality and efficiency, as confirmed in Dandara and WH Holdings. The recent jurisprudence signals three broader lessons. First, courts will rigorously police experts' qualifications, impartiality, and methodology. Second, parties drafting contracts must carefully consider the scope and separability of expert determination clauses. Third, while expert determination can provide swift resolution, it comes at the cost of limited review, with manifest error representing one of the few avenues for challenge.
Ultimately, the choice between litigation, arbitration, and expert determination reflects a balance between certainty, flexibility, cost, and oversight. Experts remain indispensable across all three, but their role shifts from assisting adjudicators to acting as adjudicators themselves. This flexibility ensures that expertise remains central to the fair and efficient resolution of modern disputes, and the lessons these cases highlight, which I have learned in my own practice, illuminate the importance of carefully selecting well-qualified, yet charismatic, experts.
Bibliography
¹ R v Mohan [1994] 2 SCR 9 (SCC).
² White Burgess Langille Inman v Abbott and Haliburton Co 2015 SCC 23, [2015] 2 SCR 182.
³ R v Abbey 2017 ONCA 640, 140 OR (3d) 40.
⁴ O’Brien v Maxar Technologies Inc 2022 ONSC 1572.
⁵ S v Ukraine International Airlines (decision of J T Akbarali J, Ontario Superior Court of Justice, 2023).
⁶ ibid [123].
⁷ ibid [128]–[129].
⁸ Dandara South East Ltd v Medway Preservation Ltd & another [2024] EWHC 2318 (Ch).
⁹ Arbitration Act 1996, s 7.
¹⁰ Fiona Trust & Holding Corporation v Privalov [2007] UKHL 40, [2007] Bus LR 1719.
¹¹ WH Holdings Ltd v E20 Stadium LLP [2023] EWHC (Comm).
¹² Veba Oil Supply & Trading GmbH v Petrotrade Inc [2002] 1 All ER 703 (CA).
¹³ White Burgess (n 2) [16]–[19].
¹⁴ Dandara (n 8).
¹⁵ WH Holdings (n 11).
¹⁶ Arbitration Act 1996, s 7.
¹⁷ Dandara (n 8).