Expert Witness Journal Issue 64 December 2025 - Flipbook - Page 27
What Makes a Good Expert?
by Guy Jackson and Jason Sharp at Overford
In construction and legal disputes, the role of the
quantum expert can be signi昀椀cant. An expert does
not just know their subject; they also understand
how to apply their knowledge in a fair, independent,
and methodical way. The credibility of their evidence
might be the di昀昀erence between success and failure
in a dispute.
Evidence and Reasoning
At the heart of a quantum analyst’s role is the
ability to work carefully with evidence and present
it through clear reasoning. This begins with
understanding how costs are recorded, testing
whether the 昀椀gures are accurate, and questioning
anomalies. Skilled analysts look beyond the surface
of ledgers, examining provisions, miscoding’s,
discounts, and hidden rebates. By contrast, weaker
analysts risk undermining their conclusions if they
rely on incomplete or selective data.
Independence, Objectivity, and
Instructions
An expert’s 昀椀rst duty is always to the tribunal or court,
not the party paying their fees, even if that party is one
of the parties to a dispute. This independence is what
gives their opinion weight. A strong expert presents
evidence without bias, resists client pressure, and
avoids drawing conclusions that cannot be properly
supported. Problems arise when experts are not
seen as impartial. In Walsh Construction v. Toronto
Transit Commission (2024), the Transit Commission
questioned the independence of Walsh’s expert due
to their repeated involvement with the contractor.
The tribunal concluded that this history created the
appearance of bias, which undermined the expert’s
credibility. The case is one of many highlighting
the importance of impartiality in expert roles. As
any good expert will know, the de昀椀nitive case on
responsibilities of an expert is that of the Ikarian
Reefer which set out the seven guiding principles of
impartial expert evidence.
Strong analysis does not stop at gathering evidence.
The best analysts build their reports step by
step, linking facts to the legal basis of the claim,
examining causation, and ensuring that any losses
claimed are not too remote. They explain their
reasoning in plain language so that lawyers, clients,
and tribunals can follow it with ease. Problems arise
when experts take shortcuts or rely on “rules of
thumb” – broad assumptions or simpli昀椀ed formulas,
such as adding 昀氀at percentages for overheads or
delay costs without testing their accuracy. Tribunals
expect tailored reasoning supported by proper
evidence, and they will discount analysis that lacks a
clear chain of logic.
In Van Oord UK Ltd v Allseas UK Ltd (2015), the
claimant’s expert was heavily criticised for failing to
check claims against the underlying documentation.
By copying sections of the claimant’s evidence
directly into his report, and attaching documents
he had not reviewed himself, he seriously weakened
his credibility. The case shows why careful handling
of evidence and logical, transparent reasoning are
essential to persuasive expert testimony.
As the Ikarian Reefer made clear, impartiality
requires not only independence in analysis but also
clarity in the instructions provided. An expert’s
duty therefore begins with obtaining clear and
comprehensive instructions. These should set out
the expertise required, the purpose and scope of the
report, the questions to be answered, the relevant
background, and the parties involved. Where
instructions are unclear, incomplete, or inconsistent
with the expert’s overriding duty to the court or
tribunal, the expert should raise these concerns with
the instructing party at the earliest opportunity. If
clari昀椀cation cannot be achieved, it may be necessary
to seek directions from the court and, in some cases,
to consider whether they can continue to act at all.
EXPERT WITNESS JOURNAL
Identifying the Basis – Cause, E昀昀ect and
Foreseeability
Every good analysis begins by identifying the
correct basis of a claim, and whether the losses
claimed are in principle recoverable. Without this
foundation, even the most detailed calculations
risk being irrelevant. A clear link between the legal
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DECEMBER/JANUARY 2025-2026
