Expert report not annulled due to expert’s failure to be registered: clarifications from the Cour de cassation

One autumn morning, in the premises of a commercial rent judge at the tribunal de grande instance of Paris, two companies argued over a crucial point: what should be the rent for a renewed commercial lease? To resolve the matter, the judge ordered a court-appointed expert report. The appointed expert delivered his report. But a technical detail arose: the expert, who was not on the national list of experts nor on that of any cour d'appel, had taken an oath... in writing, and not in court. One of the parties seized the opportunity to request that the report be declared void. The cour d'appel dismissed the application. The Cour de cassation affirmed. Why? Because not every irregularity is a fatal defect. This is the lesson of the decision of 26 September 2019.

In property proceedings, the expert report is often the pivot of the dispute. Its reliability determines the sale price, the eviction indemnity, or the amount of the revised rent. Thus, challenging the report on a mere procedural defect may seem a tempting strategy. But the supreme court draws a clear line: only irregularities affecting substantial formalities or public policy can result in nullity. Others, such as an irregular oath-taking, cannot succeed. This is what landlords, tenants and professionals must now keep in mind.

This decision from the Quai de l’Horloge resounds strongly in the countless rental disputes that dot the capital. Landlords and tenants will find valuable confirmation: procedural formalism is not an automatic trap. But one still needs to understand its subtle mechanics.