Court-appointed expert evidence (expertise judiciaire)

Court-appointed expert evidence is the investigative measure by which the court entrusts a technical expert with the task of informing it on a question of fact that requires knowledge the court does not possess. It is governed by Articles 232 et seq. of the Code of Civil Procedure, which organise investigative measures carried out by a technical expert, and by Articles 263 et seq. for expert evidence proper. In intellectual property, it is most often used to assess whether a product or process implements a patent, to compare software or to assess loss.

Conditions for ordering an expert report

The court orders expert evidence only where findings or a consultation are insufficient, and it may not appoint an expert to make up for a party’s failure to adduce evidence. The expert must never express a legal assessment, so that it is not for the expert to say whether a product infringes a patent, but to describe the technical features of the product and compare them with those set out in the claims, under the supervision of the court, which alone retains the interpretation of the title. Expert evidence may be ordered before any proceedings, under Article 145 of the Code of Civil Procedure, where there is a legitimate reason to preserve or establish evidence of facts on which the resolution of a dispute might depend, a measure known as an in futurum evidentiary measure.

Conduct of the expert’s work

The expert carries out the task in compliance with the adversarial principle: the expert summons the parties, communicates to them the documents collected, responds to their written observations, known as “dires”, and records everything in a report. The expert may seek the opinion of another technical expert in a different field, which is frequent where the task combines technical analysis and an accounting assessment. The parties are assisted by their counsel and, in practice, by technical advisers. The protection of confidential information exchanged during the work justifies setting up a confidentiality club or restricted access arrangements, in particular where trade secrets are at stake.

Weight of the report

The court is not bound by the expert’s conclusions, but it rarely departs from them without detailed reasons. The report once filed may be challenged by a request for a supplementary or new expert report. In patent matters, the expert’s role is circumscribed by the figure of the person skilled in the art, an abstract reference whose knowledge the expert sheds light on without taking its place. In assessing damages, an accounting expert report is frequently ordered after the judgment on infringement, where the documents produced do not make it possible to determine the volume of infringing goods and the margins.

Key points

Court-appointed expert evidence informs the court on technical or accounting facts, without ever deciding questions of law. It is adversarial, often lengthy and costly, and the court freely assesses its conclusions. Instruct a technical adviser early, organise the protection of confidential information and draft the requested heads of the expert’s task precisely, since a poorly drafted task leads to an unusable report.

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This glossary entry is general in scope and does not constitute legal advice.

Dhenne Avocats litigates patent disputes before the Paris Judicial Court, the Paris Court of Appeal and the Unified Patent Court. When the question arises in a real case, the right moment is almost always before proceedings are issued.

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