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Korean Supreme Court Details Standard for Establishing Doctrine of Equivalents Infringement
Summary of the Key Issues and Holdings of Korean Supreme Court Ruling (2019Da237302). Patentee A brought an infringement suit against B, alleging that one of B’s products was infringing A’s patent for a “detachable handle for cooking vessels.”
The Korean Patent Court ruled that, even though some parts of B’s product had been changed from A’s patented product, their solution principles and effects were substantially identical, and a person of ordinary skill in the art (“POSITA”) would readily be able to come up with such changes. After the Patent Court ruled in favor of the patentee by finding DoE infringement, the case was subsequently appealed to the Korean Supreme Court. The main issue in dispute on appeal was the meaning and standards for the “substantially identical solution principle” and the “substantially identical effect principle” for establishing DoE infringement.”
With regard to the first DoE factor, namely the “substantially identical solution principle,” the Korean Supreme Court ruled that:
“when determining whether the solution principle of an infringing product is substantially identical to that of a patented invention, courts must practically
[1] In Korea, an accused product that includes a modified element as compared with a patented invention may still be infringing under the DoE when the accused product has: (1) a substantially identical solution principle with the patented invention; (2) accomplished substantially identical effect to the patented invention despite some elements being different; and (3) modifications that would have been obvious to a POSITA (“person of ordinary skill in the art”). However, DoE infringement may not be established if (4) an accused product comprises technology already publicly disclosed before the filing of the patented invention, or a POSITA can easily conceive from the publicly known technology, or (5) the prosecution history of the patented invention indicates that the modified element of the invention for review was consciously excluded from the claims of the patented invention. As for the second DoE factor, namely the substantially identical effect principle, the Korean Supreme Court held that: “Determination of whether the effects [of the infringing product and patented invention] are substantially identical shall be based primarily on whether the infringing product solves the same technical issue solved by the patented invention which had not been solved by prior art. Therefore, in principle, if the core technical idea forming the basis for the unique solution of the patented invention (in light of the description of the invention found in the specification and publicly known technology at the time of the invention’s filing) is also found in the infringing product, then their effects shall be deemed to be substantially identical as well. If such core technical idea had been actually or effectively publicly disclosed before the filing of the patented invention, however, then the core technical idea was neither unique to the patented invention, nor did it solve the technical issue which had not been solved by prior art. In such case, the determination for the DoE factor (ii) should not be based on whether the core technical idea was found in the infringing product; instead, the determination should be made by comparing the individual functions or roles of the elements which the DoE issues hinge upon.”