Swiss Federal Supreme Court Clarifies
the Scope and Probative Value of Private
Expert Opinions Obtained by the Parties
Under the Revised Article 177 CPC
(4A_42/2026, 22 April 2026)

In a recent decision to be included in the official collection, the Swiss Federal Supreme Court clarified that all medical reports produced by the parties - including unsupported certificates of incapacity for work issued by treating physicians – qualify as documentary evidence within the meaning of the revised Article 177 of the Swiss Code of Civil Procedure ("CPC"). The Court held that the recognition of such documents as evidence does not, however, prejudge their probative value, which remains subject to free judicial assessment in each individual case.

Under the former Article 177 CPC, written documents such as writings, drawings, plans, photographs, films, sound recordings, electronic files and the like, capable of proving relevant facts, constituted documentary evidence. However, notwithstanding the above, private expert reports as well as medical certificates were deemed mere party's allegations and thereby did not constitute documentary evidence as such. As a result, such documents were devoid of any independent probative value. With the revision of Article 177 CPC, private expert opinions obtained by the parties are now encompassed within the scope of documentary evidence and therefore no longer deemed as mere party allegations. The Federal Supreme Court confirmed in this ruling that medical certificates obtained by the parties also fall within the scope of this provision.

The Court's key findings can be summarised as follows:

All Party-Produced Medical Reports Qualify as Documentary Evidence (Art. 177 CPC)
According to the Court's findings, the revised Article 177 CPC encompasses not only written formal private expert opinions, but all medical opinions produced by the parties, including physicians'' certificates of incapacity for work. The drivers for this finding were:

• The alignment of Article 177 CPC is consistent with case law on social insurance law where such certificates are treated as evidence. With this, the Court underlines the legislative intent to align the evidentiary regimes of civil procedure and social insurance law.
• A contrary interpretation would be impractical: it would be artificial to recognise the status of documentary evidence for formal private expert opinions while denying it to simple certificates from treating physicians, which constitute the bulk of the evidence in disputes concerning daily allowance benefits and other health-related employment claims.

Probative Value Remains Subject to Free Judicial Assessment
The Swiss Federal Supreme Court explicitly specified that the characterisation as documentary evidence under Art. 177 CPC does not affect the court’s assessment or weighing of that evidence. Accordingly, documentary evidence does not, by itself, establish the alleged fact as proven. In this regard, the Court held that:

• The court freely assesses the probative value of each medical opinion on a case-by-case basis, consistent with the principle of free evaluation of evidence.
• An unsupported certificate of incapacity for work issued by a family physician will rarely, on its own, establish a contested incapacity for work.
• Drawing on social insurance case law, the Court recalled that treating physicians are primarily focused on providing therapy and that, as experience shows, they tend in case of doubt to rule in favour of their patients – a factor that objectively reduces the probative value of their attestations in litigation.

This ruling confirms the significant shift in the evidentiary landscape of Swiss civil procedure with the revision of Art. 177 CPC. It serves as an important reminder that the submission of private expert reports pursuant to Art. 177 CPC does not cause the discussion on evidentiary value to close. Rather, the probative value of such documents must be evaluated by the judge during the overall assessment of evidence. Parties must therefore ensure, as far as possible, that the facts for which they bear the burden of proof are substantiated through multiple forms of evidence; reliance on a single document may not be sufficient.