EWJ 60 April 2025 web - Journal - Page 70
Expert Witness Case Study: Is it
Possible to be an Expert in Everything?
The role of an expert witness is critical in modern litigation, particularly in cases involving
financial regulatory disputes, fraud, or complex transactions. However, as the scope and complexity of such cases expand, a fundamental question arises: can one individual realistically
serve as an expert in multiple aspects of a case? This challenge is particularly evident in both
recent and ongoing high-profile, complex trials involving allegations such as market-rigging of
interest rate benchmarks and “Cum-Ex” dividend arbitrage trading. Our experience in such
cases, across multiple jurisdictions, offers a more nuanced perspective on effectively utilising
expertise in the courtroom.
expert has ventured beyond their area of expertise or
drawn conclusions that lack a solid foundation. Such
tactics can weaken the credibility of the expert’s testimony and influence the court’s perception of the
reliability of their opinions.
The Complexity of Modern Financial Trials
In these financial “super-trials”, the complexity of the
underlying issues can be staggering. Such trials require the court to understand many issues, which may
include tax law, cross-border financial transactions,
complex trading strategies, financial market infrastructure, trading software and information providers,
compliance and regulatory frameworks, forensic accounting and accepted market practice. It is exceedingly rare for an individual expert to possess the
depth and breadth of knowledge necessary to comprehensively address such an array of subjects. Even
the most qualified professionals typically specialise in
only one or two areas.
l Practical Constraints: Preparing for cross-exami-
nation on a broad range of topics is an enormous burden for a single individual. The risk of being
discredited on a tangential issue increases significantly.
l Data Management Challenges: The sheer scale of
analysis, such as sifting through data rooms containing
millions of documents further strain the capabilities
of a single expert to be able to respond to precise,
detailed cross-examination.
Traditionally, expert opinions were often provided by
academics or generalist consultants, but there is now
a growing emphasis on engaging ex-practitioners to
offer insights into market practices, which are invaluable to both lawyers and their clients. The emergence
of this ‘market practice expert’ is a relatively recent
phenomenon and in this series of blog posts we delve
deeper into the role, challenges and potential improvements of how such experts might be utilised.
These challenges underscore the potential for errors
or omissions, even with the most diligent experts.
Teamwork in Expert Testimony
Therefore, the question arises: should courts permit
or even encourage the use of expert teams to ensure
all facets of a case are addressed? Instead of relying on
a single individual, a team of specialists can divide
responsibilities according to their expertise. For
example, in this case:
The Limitations of the Single Expert Model
We understand that the standard model of relying on
a single expert witness has its strengths, particularly
in terms of clarity and accountability. A lone expert is
easier to cross-examine and can provide a unified narrative for the court. However, we believe this model
also has significant limitations. Taking the “Cum-Ex”
trials as an example and concentrating solely on what
may be considered as the ‘market practice’ element of
the case (which may appear on the face of it to be a
narrow definition), expertise would be required on
the following topics: dividend arbitrage, derivatives
pricing, double tax treaties, equity market infrastructure, stock borrowing and lending, custody chains,
middle and back-office procedures, KYC and AML
checks, as well as thorough knowledge of specific EU
Regulations and the FCA Handbook.
l a derivatives trader could simplify and add clarity to
complex trading strategies;
l an experienced custodian could provide the neces-
sary insight into chains of custody; and
l a compliance specialist could evaluate adherence to
local and cross-border regulations
By pooling knowledge, such teams can offer a more
robust and reliable testimony. However, we recognise
the use of expert teams presents its own challenges,
in particular for the courts who must consider questions of admissibility and coordination, thereby requiring effective collaboration and clear delineation of
responsibilities.
Court Recognition of the Role of Research and
Collaboration
Even when a single expert is engaged, extensive
research and collaboration are often required to fill
knowledge gaps. Many experts rely on their networks
As a result, several issues can arise over the course of
an expert’s engagement.
l Overextension of Expertise: Experienced crossexaminers may seek to highlight instances where the
EXPERT WITNESS JOURNAL
68
APRIL 2025
