In the United States and many other countries, it’s common to mark patented products with the patent number. Although marking is not required, it’s beneficial because marking serves as constructive notice to the world that the product is patented. Thus, damages for patent infringement can begin to accrue on the data that the patent holder began marking its product in a continuous and conspicuous manner — even if the infringer had no actual notice of the patent at the time.
Falsely marking a patent product, however, can create liability. Anyone who falsely marks an unpatented product with a patent number for the purpose of deceiving the public violates Section 292 of the Patent Act and risks liability.
It’s common for companies to list a “lanudry list” of patents on a product, and patent numbers often remain on the product after the patent expires. However, this practice creates a risk of liability. According to the Federal Circuit, an “unpatented article” is one not covered by at least one claim of each patent with which the article is marked. Thus, whenever a product design changes, companies should review the patent markings to ensure that the patent still covers the product. Also, the Eastern District of Virginia recently answered “yes” to to the question of whether an expired patent can give rise to a false marking claim. In Pequignot v Solo Cup, the court held that going forward from the date of a patent’s declaration, an article becomes “unpatented.”
Liability under Section 292 still requires evidence of bad faith. Since bad faith can be a subjective determination, patent holders should regularly review their product lines and remove expired patent numbers, as well as patent numbers that no longer cover the current product, from their marking protocol.