Trends in Expert Witnessing: Cross-Border Experts

As cross‑border disputes proliferate in areas like intellectual property, antitrust, and environmental regulation, expert testimony is increasingly becoming an international pursuit. While once an exceptional practice, bringing in U.S.-based experts is steadily becoming routine. International arbitral institutions are codifying procedures for admitting foreign experts, while national courts are showing greater willingness to recognize overseas credentials when methodology is transparent.

From Exception to Expectation

For much of the modern era, cross-border engagements were fairly rare. When they did occur, they were treated as exceptions—logistically complex, procedurally uncertain, and sometimes viewed with skepticism by judges and parties alike. Over the past two decades, however, several forces have reshaped the landscape, turning international work from a rarity into a growing norm:

• Globalization of disputes: Intellectual property, antitrust, and environmental cases increasingly span multiple jurisdictions.
• Institutional codification: Arbitral bodies like the ICC and UNCITRAL have formalized procedures for admitting foreign experts.
• Judicial openness: Courts in common law jurisdictions show greater willingness to recognize overseas credentials when methodology is transparent.
• Emergence of transnational expert pools: Certain technical fields now rely on a small cadre of experts who testify regularly across borders.
• Shift in expectations: What was once an exception is now anticipated in complex, high-value disputes.

This evolution marks a departure from the past: cross-border testimony as a professional practice increasingly woven into the fabric of high-stakes global litigation and arbitration.

Disputes Without Borders

Experts are being called into proceedings that span continents, where their analyses must resonate with audiences who bring different legal traditions and cultural expectations. The expectation is that experts can adapt their practice to fit international fora. Therefore, cross‑border testimony requires preparation that accounts for credential recognition and the differences in how expertise is perceived outside the United States.

Intellectual property is a prime example. Patent disputes involving multinational corporations often require experts to testify in both U.S. courts and foreign tribunals. A pharmaceutical patent case might involve proceedings in the U.S., Germany, and Japan simultaneously, with experts expected to explain technical details in ways that resonate across different legal traditions.

Antitrust litigation also illustrates the trend. Global mergers (such as airline alliances) are reviewed by regulators in multiple jurisdictions. Experts in economics or market analysis may be called to testify before U.S. agencies and European competition authorities. The methodologies may be familiar, but the expectations differ: U.S. courts emphasize Daubert‑style gatekeeping, while EU proceedings often rely on judicial discretion.

Environmental disputes highlight another dimension. Climate change litigation and transnational pollution cases often involve experts testifying about impacts that cross borders, such as emissions affecting multiple countries or water contamination flowing downstream into another jurisdiction. Here, experts must situate their analysis within international treaties, not just domestic standards.

Institutional Codification

Signs that cross‑border expert work is becoming routine include institutions codifying rules for how experts are appointed, how their reports are structured, and how their testimony is received. This codification reduces uncertainty for tribunals and parties, while setting expectations for experts themselves. The International Chamber of Commerce (ICC) has taken a leading role. Its Expert Rules (revised in 2021) provide a framework for the appointment of experts, the administration of expert proceedings, and the conduct of joint meetings and reports. For U.S. experts, this means that when they step into ICC arbitration, they can expect standardized procedures governing disclosure, timetables, and the scope of their mandate, rather than improvisation by counsel or tribunal.

Similarly, revisions to the UNCITRAL Arbitration Rules have become a touchstone for cross‑border disputes. They establish the tribunal’s authority to appoint experts and require parties to cooperate in providing information. This codification signals to experts that their role is recognized within a global procedural framework, even if the details vary by tribunal.

Recent trade and investment treaties also reflect this movement. The EU–Canada Comprehensive Economic and Trade Agreement (CETA), for example, establishes a permanent tribunal system for investor–state disputes, with procedural rules that anticipate the use of expert evidence in areas such as environmental protection, labor standards, and technical regulation. Similarly, the United States–Mexico–Canada Agreement (USMCA) includes dispute resolution chapters where panels are empowered to call upon experts to clarify complex issues ranging from sanitary and phytosanitary measures to digital trade. These frameworks matter because they embed expert testimony into the treaty architecture itself rather than leaving evidentiary practice to ad hoc tribunal discretion.

Methodological Convergence

While all international fora are different, engagements increasingly demand similar forms of expert evidence. Written reports are typically expected to follow a structured format, laying out methodology, assumptions, and sources in a way that is transparent and reproducible. This mirrors the adversarial traditions of common law jurisdictions but has been absorbed into civil law proceedings and arbitral practice as well.

Transparency has become a near-universal feature. Economic experts in EU competition cases, for example, must disclose their models and datasets in detail, allowing judges to scrutinize the reasoning behind conclusions. Techniques such as concurrent testimony—sometimes called hot‑tubbing—are structurally transparent and have spread from Australian practice into international arbitration creating a hybrid style of presentation that blends adversarial and inquisitorial traditions. Alongside this, independence declarations are now standard, reinforced by professional guidelines like the IBA Rules on Expert Evidence, which encourage experts to state explicitly that they are not advocates for the party who retained them.

Digital integration has accelerated this convergence. Remote testimony, electronic submissions, and secure data rooms have forced experts to adapt to standardized formats that can be used across jurisdictions. U.S. experts abroad increasingly encounter familiar expectations—structured reports, transparent data, and readiness for cross‑examination—regardless of whether they are testifying in London, Paris, or before an arbitral tribunal in Singapore. This convergence smooths participation across borders and signals that expert methodology itself is becoming transnational. Nevertheless, it is crucial that experts always check with their engaging attorney to clarify any differences when encountering a new forum.

From Gatekeepers to Gateways

Civil law jurisdictions historically resisted party‑retained experts, especially from abroad. In French commercial litigation of the 1990s, judges relied exclusively on experts judiciaires (court‑appointed experts). American engineers could not usually be admitted, because the system viewed party‑retained experts as biased—from within France or otherwise. Similarly, in German product liability cases, U.S. technical experts were dismissed outright if they lacked local licensure, even when their analysis was central to the dispute. Scholarly commentary from comparative law reviews of that era noted that foreign experts were “rarely heard” in continental courts, reflecting a closed posture.

In contrast, recent practice shows openness. In UK patent litigation (Unwired Planet v. Huawei, 2017), U.S. telecommunications experts were admitted to testify on global licensing practices, with the High Court explicitly recognizing the relevance of expertise drawn from outside the UK. In EU competition proceedings (Intel v. Commission C‑413/14 P), economic experts from the U.S. were accepted to provide market analysis, with the Court of Justice emphasizing the importance of transparent methodology over national origin.

A Global Rolodex

In addition to legislation and codification, the rise of transnational expert pools—structured rosters and networks that courts and tribunals can draw on—represent a more systematic way of integrating expertise into international proceedings.

• Expert witness referral agencies: Agencies like Round Table Group are a low-friction source for high-quality experts experienced in cross-border engagements.
• ICC expert rosters: The International Chamber of Commerce maintains curated lists of experts in fields like engineering, finance, and environmental science. U.S. specialists are included and can be appointed directly into disputes seated anywhere in the world.
• ICSID appointments: The International Centre for Settlement of Investment Disputes revised its rules in 2022 to formalize how tribunals appoint experts. This ensures that American scientists, economists, and engineers can be tapped for investor–state disputes across Latin America, Africa, and Asia.
• European patent litigation: Courts in the UK and continental Europe increasingly rely on blended pools of technical experts, drawing on U.S. biomedical and telecommunications specialists alongside
• European counterparts:This creates a de facto transnational pool in industries where innovation is global.
• Professional guidelines: The International Bar Association’s rules on expert evidence encourage tribunals to consider experts from multiple jurisdictions, reinforcing the legitimacy of transnational rosters and reducing procedural friction for U.S. experts.

Conclusion

The trajectory of U.S. experts abroad reflects a transformation in judicial and arbitral practice; what began as sporadic acceptance has matured into structured participation through codified rules, transnational pools, and converging methodologies. The trend is not uniform—fora differ in how they integrate outside specialists—but the overall trend is clear: cross-border experts are becoming an increasingly important part of international litigation.

For over 30 years, Round Table Group has been connecting litigators with skilled and qualified expert witnesses. If you are interested in being considered for expert witness opportunities, contact us at 202-908-4500 for more information or sign up now!