Why do civil-law systems treat parties and experts as separate sources of evidence?

In civil-law systems, parties and experts are treated as distinct sources of evidence primarily to ensure the impartiality and technical integrity of the judicial process.

Unlike common-law systems, where experts are typically designated by the parties and function similarly to ordinary witnesses, civil-law jurisdictions generally empower the court to select experts from an approved list. This practice is designed to guarantee that the expert serves as an impartial auxiliary of the court rather than as an advocate for a specific side. Because their role is to provide objective technical or scientific analysis, experts are often separated from the parties, who are viewed as having a vested interest in the outcome.12

Furthermore, many civil-law systems do not categorize parties as witnesses. This distinction is based on the belief that a party’s testimony in their own favor is inherently biased and likely to be discounted, while compelling a party to testify against themselves is considered unduly harsh. Consequently, while parties may be questioned informally by the court, the expert remains a separate, court-appointed source of evidence intended to provide neutral expertise on complex matters.2