Of all the questions a party new to arbitration asks when engaging an expert, "can we structure the fee around the outcome?" comes up more often than most practitioners might expect — usually from contractors or private clients accustomed to conditional or success-based arrangements in other professional contexts, and looking to manage cash flow on an expensive claim. The answer, for expert witness engagements, is a firm no — and understanding why is important for anyone instructing or relying on expert evidence.
The basic principle
An expert witness should not undertake an appointment on any form of conditional or success-based fee arrangement — an arrangement where the remuneration, however fixed or calculated, depends on the outcome of the proceedings or on the nature of the evidence given. This principle applies regardless of whether the party instructing the expert is itself engaged on a similar basis, such as a contingency arrangement with its own legal counsel. Whatever fee structure sits elsewhere in the case, the expert's own remuneration should not be tied to the result.
Why this matters more for experts than for other professionals
A conditional fee arrangement is a familiar and, in many jurisdictions, entirely legitimate way of aligning an advocate's or lawyer's incentives with a client's success — it is, after all, the advocate's job to pursue the client's interests as far as the rules permit. That alignment is precisely what makes the same arrangement inappropriate for an expert witness. The expert's evidential value depends entirely on being seen to have no stake in which way the tribunal's decision falls. An expert being paid more, or paid at all, only if the case succeeds has a direct and obvious financial interest in reaching — and defending — conclusions that favour the instructing party. Even where the expert's professional integrity would, in fact, hold firm against that pressure, the mere existence of the arrangement invites doubt that is very difficult to dispel once raised.
Tribunals and cross-examining counsel are alert to this. A fee arrangement that could be characterised as tying remuneration to outcome is a natural and legitimate line of cross-examination, and one that can do lasting damage to an expert's credibility regardless of how sound the underlying technical analysis actually is.
Appropriate fee bases
The accepted alternatives — an hourly rate or a fixed fee, agreed and documented before work begins — should form the basis of any expert witness engagement. These structures carry no inherent connection between the expert's remuneration and the outcome of the case, which is precisely the point. This should be confirmed in writing at the outset of the engagement, as discussed in Part 3 of this series, and reflected in the expert's formal declaration accompanying the eventual report, which typically includes a specific confirmation that no conditional or other success-based fee arrangement is in place.
The narrow exception: dual-role engagements
As discussed in Part 14, the one context in which a conditional fee may be tolerated is where a professional is genuinely and properly acting in a permitted dual role — as both advocate and expert witness in a lower-tier tribunal where that dual role is allowed. In that limited circumstance, a conditional fee arrangement may be acceptable, but only insofar as it is understood to attach to the advocacy component of the role rather than the expert evidence itself, and it must be declared to the tribunal. Even then, if the matter is transferred to a higher tribunal where the dual role is no longer available or appropriate, any previously agreed conditional fee arrangement typically needs to be replaced with an hourly rate or fixed fee before the expert continues in that separate capacity. This exception has no application to the significant construction and infrastructure disputes handled through DIAC, the DIFC Courts, or arbitrateAD, where dual-role arrangements are rarely, if ever, appropriate.
What lawyers and clients should confirm before instructing
When selecting and instructing a construction or engineering expert, confirming the fee basis in plain terms is a small but important part of due diligence:
- Is the fee structured as an hourly rate or a fixed fee, clearly unconnected to the outcome?
- Is this confirmed in the written terms of engagement, not left as an informal understanding?
- Will the formal declaration accompanying the eventual report include express confirmation of the fee basis?
An expert who hesitates or equivocates when asked directly about fee structure is worth pausing over before instructions are confirmed.
A note for contractors managing cost pressure
The instinct to seek a contingency-linked fee arrangement for an expert is usually a genuine attempt to manage financial risk on an expensive claim — an entirely understandable commercial concern, particularly for contractors and engineering businesses weighing the cost of a dispute against constrained project cash flow. But the risk this creates to the credibility of the expert evidence itself is generally far greater than the cash-flow benefit it offers. Cost management on expert fees is better pursued through clear scoping, efficient instructions, and proportionate engagement (as discussed earlier in this series) than through a fee structure that puts the evidential value of the report itself at risk.
Part 16 turns to a related but distinct topic: expert witness immunity — what protection experts actually have for the opinions they give, and what falls outside that protection.