In Taiwan’s patent infringement litigation, an accused infringer asserting prior user rights as a defense must provide convincing evidence to prove that, before the patent’s filing date, they had already implemented the relevant technology or had completed the necessary preparations in Taiwan, so as to be exempt from the patent’s exclusive rights. (Article 59.1.3 of the Taiwan Patent Act.)
For inventions related to devices, asserting prior user rights typically requires proving that the technical features implemented in the accused product are identical or substantially identical to the claimed features of the patent in dispute. Additionally, it must be demonstrated that the product was already manufactured or sold or that the necessary preparations had been completed before the filing date of the patent.
Notably, Taiwan’s Intellectual Property and Commercial Court has further advanced this rule in favor of prior users. In a May 2024 decision, the Court indicated that, even if an accused product was manufactured or sold after the patent’s filing date, the defendant may still successfully assert prior user rights—provided that they can prove that the accused product shares the same technical features as another product that they manufactured or sold before the filing date. This decision serves as a notable precedent, illustrating how continuity of technical features can be leveraged to establish prior user rights.
In this case, the defendant was unable to directly prove that the accused product had been manufactured and sold before the filing date of the patent in dispute. However, the defendant presented a series of evidence demonstrating that, years before the filing date, they had manufactured and sold other products incorporating the claimed features of the patent in dispute.
Furthermore, the defendant proved that the accused product also shares these same features, thereby indirectly establishing that it is exempted from infringing the patent. Even though the accused product is not identical to the previously manufactured products, the court ruled that as long as the technical features are the same, the defendant could still successfully assert prior user rights as a defense.
This ruling confirms that even if a product undergoes modifications, as long as the core technical features remain the same, prior user rights can still be asserted based on previous implementation of those technical features to avoid patent infringement liability.
Moreover, the court’s acceptance of prior user rights as a defense depends heavily on the strength of the supporting evidence. Taiwan imposes a relatively strict burden of proof on the defendant in such cases. Therefore, companies should preserve thorough records of their technological developments and provide evidence that links the technical features to the dates of implementation, such as export declarations, product catalogs or webpages, product installation manuals, etc., to ensure effective assertion of prior user rights in a patent infringement dispute.