In a patent infringement action, the Korean Supreme Court held that the defendant’s statement at the first-instance stage that its accused product contained all of the elements of the plaintiff’s patent claims constituted an “open-court admission” and, unless lawfully withdrawable, is legally binding (Supreme Court Case No. 2026Da202753, rendered July 16, 2026).

▶ Background of the Case

The subject patent relates to an electrode plate-stacking apparatus for use in manufacturing secondary batteries. The patentee brought a patent infringement action, alleging that the secondary battery equipment manufactured and sold by the defendant infringed the patent.

The court of first instance (Seoul Central District Court) held that the patented invention lacked inventive step over the prior art and was therefore subject to grounds for invalidation. It further held that the plaintiff’s claims for an injunction against infringement, based on a patent subject to grounds for invalidation, constituted an abuse of rights, and accordingly rendered judgment in favor of the defendant, even though the defendant admitted that its accused product was identical to the patented invention.

▶ IP High Court Decision

Unlike the court of first instance, the IP High Court held that the patented invention did not lack inventive step and it accordingly rejected the defendant’s abuse-of-rights defense based on the alleged lack of inventive step.

Meanwhile, the defendant argued that its admission made at the first instance based on a “personal claim analysis/evaluation” and was made by mistake, and, therefore, should be allowed to be withdrawn.

The IP High Court disagreed. It considered that a statement based on the accused’s own claim analysis or evaluation as to whether each corresponding element of the accused product was identical or equivalent to the corresponding element of the patented invention must have been determined by comprehensively considering various relevant factors and the statement or admission was voluntarily made during the course of the court proceedings. Accordingly, the Court determined that the defendant’s statement that the accused product contained all of the elements of the patented invention was an admission that was judicially binding.

The Court further opined that a party seeking to withdraw a judicial admission must prove both that the admission was contrary to the principle of good faith and that it was made by excusable mistake. The Court found that the evidence and circumstances submitted by the defendant were insufficient to establish that the admission met the withdrawal requirements.

Accordingly, the IP High Court determined that the accused product contained all of the elements of the patented invention and thus fell within the scope of the patent.

▶ Supreme Court Decision

The Supreme Court upheld the IP High Court’s decision concerning the defendant’s legally binding or judicial admission.

The Court reaffirmed the established legal principle that, in a patent infringement action, whether a product manufactured by the accused party contains certain elements is a primary fact underlying the determination of infringement and may therefore be the subject of a judicial admission; and that, once established, such an admission becomes legally binding unless lawfully withdrawn.

 Accordingly, the Supreme Court held that the defendant’s statement made at the first instance constituted a judicial admission in the absence of any evidence justifying the withdrawal thereof; and upheld the IP High Court’s decision.