Matthias Cazier-Darmois


20 Rue Cambon
75001, Paris, France


Peers and clients say:

"He has established a robust reputation as an expert witness in international arbitration"
"Matthias is a tremendously smart and hard-working expert"
"A leading figure in the field here in France"


Matthias Cazier-Darmois is a partner at HKA with 20 years of experience in providing expert evidence and valuation advice in complex commercial disputes and international arbitrations.

What do you enjoy most about working as an expert witness in arbitration proceedings?

Never getting bored. Each case presents unique combination of issues, industries and cultures. There is always a huge amount of knowledge to be gained in each and every case.

Where, in your opinion, does the future of the practice area lie?

The sophistication of damages quantification has increased enormously in the past decade. Today the familiarity of counsels and arbitrators with damages-related issues is stunning.

At the same time, the answers brought by different tribunals to damages issues in analogous contexts can be very different. Going forward, I could see greater convergence, especially as damages are increasingly a topic of research and debate among arbitration practitioners.

What qualities make for an effective arbitration expert witness?

Aside from being skillful at conveying complex messages to a non-expert audience, a key attribute of a good expert witnesses is his or her ability to quickly make sense of the (sometimes enormous amount of) economic data typically found in international arbitration cases. Understanding the evidence is key to building a robust analysis from the outset.

This is easier said than done: getting a good grasp of the facts is time-consuming and requires articulating technical knowledge (such as interpreting accounting and financial documents), knowledge of the subject industry, and an understanding of the parties’ legal cases.

Third-party funding is a growing trend. What difficulties are posed by performing quantum due diligence analyses on behalf of third-party funders?

I have seen very different approaches taken by different third-party funders. Some doing extensive due diligence, including on quantum. Others being less risk averse.

At present, my sense is that there is more money to fund arbitration cases than meritorious cases require. This is good for claimants, but challenging for funders’ returns.

I am looking forward to seeing some funds diversify to bring meritorious cases before French courts – although, unfortunately, funding is probably not the only challenge faced by claimants in the French legal system.

What are the greatest challenges currently facing financial and economic experts?

To an extent, some of the greatest challenges are behind us. Kudos to the pioneers, who first educated tribunals about the “compounding” of interest, the “discounting” of future losses, or the “cash flows” typically used by investors to assess the value of an investment.

Many key concepts are now well understood and, perhaps partly as a result, expert evidence is seen as more commoditised, resulting in more competition in the market.

At the same time, damages are less often overlooked, and the increased sophistication of parties, counsels and tribunals means that parties really need to get it right, allowing reliable experts to thrive.

What advice would you give to someone starting out a career in your field?

Get a job at HKA, and one or more mentors. I have been very fortunate to work with many exceptional expert witnesses. With them, I have attended dozens of hearings before getting my first appointments. This helped me building my expertise and developing long-lasting relationships with practitioners in the field. I am grateful to them and looking forward to giving back by pushing the next generation of experts.