EPO clarifies public availability of a black-box disclosure

In the recent decision G 1/23, the EPO’s Enlarged Board of Appeal (EBA) clarified the prior art status of a product put on the market before the filing date of a European patent application, where the composition or internal structure of the product could not be determined or reproduced prior to the filing date.

The wording of an earlier EBA opinion (G 1/92) has led to diverging case law interpretations, one of which held that a marketed product that is not reproducible is not state of the art, while another concluded that only the composition/internal structure of the product is not state of the art. The interpretations stem from G 1/92’s focus on a requirement for reproducibility of prior art teachings.

Ultimately, the EBA held that neither interpretation is correct, in a decision issued on July 2 2025.

The board found that the reproducibility requirement establishes a legal fiction as it “contradicts everyday experience”. The EBA also found that both interpretations ignore that the skilled person ultimately relies on the availability of natural products that can be readily acquired but not necessarily reproduced; for instance, the chemical elements.

The board concluded that a product put on the market is not excluded from the state of the art merely because its internal structure or composition cannot be analysed. Moreover, the EBA found that technical information derivable from such a product is also state of the art even if it could not be analysed and reproduced. Put more simply: the product’s composition or internal structure is also state of the art.

The EBA acknowledged that it may be difficult to establish the exact technical teachings derivable from a previously marketed product but regarded this as a “practical legal problem of proof for the lawyer”.