Key Insights from Korea's Supreme Court Ruling 2022Hu10210

A recent South Korean Supreme Court decision, 2022Hu10210, delivered on February 2, 2023 (hereinafter "the Decision"), has reaffirmed and clarified crucial legal principles regarding the application of the "doctrine of equivalents"—a pivotal concept in patent infringement assessments. The Decision is particularly noteworthy for providing specific guidance on the timing for assessing the "ease of alteration" of a component and the criteria for judging whether a specific component was "consciously excluded" during patent prosecution.

This ruling offers valuable insights for patent holders and potential infringers alike, shaping how the boundaries of patent protection are understood and enforced in Korea.

1. The Doctrine of Equivalents: Purpose and Core Requirements

As a fundamental principle, the scope of a patented invention is determined by the claims as written (Korean Patent Act, Article 97). However, in practice, infringers rarely copy a patented invention literally; they often make minor modifications to avoid direct infringement. To address this, courts have long recognized the doctrine of equivalents, which allows a finding of infringement even if the accused product or process does not literally fall within the claims, provided it is "substantially the same" as the claimed invention.

According to established Supreme Court precedents (e.g., Supreme Court Decision 2012Hu1132, rendered July 24, 2014; Supreme Court Decision 2017Hu424, rendered January 31, 2019), the following conditions must be met for the doctrine of equivalents to apply:

1. Same Problem-Solving Principle: The patented invention and the accused product/process must share substantially the same principle for solving the technical problem.
2. Same Function and Effect: Despite any alterations, the accused product/process must produce substantially the same function and effect as the patented invention.
3. Ease of Alteration: The alteration must be such that a Person Having Ordinary Skill In The Art (PHOSITA) in the relevant technical field could have easily conceived of it at the relevant time.
4. Non-Obviousness over Prior Art: The accused equivalent must not itself have been known or obvious from the prior art at the time of the patent application. The doctrine cannot be used to improperly extend patent protection to cover what was already in the public domain.
5. No Prosecution History Estoppel (Conscious Exclusion): The patentee must not have intentionally excluded the specific altered configuration from the scope of the claims during the patent prosecution process.

2. Timing for Assessing "Ease of Alteration": The "Time of Trial Decision" Standard

A key clarification in the 2022Hu10210 Decision concerns the point in time for judging the "ease of alteration" (condition 3 above) in a scope confirmation trial (a proceeding before the Korean Intellectual Property Office (KIPO) to determine if an accused product falls within the patent scope).

The Supreme Court explicitly reaffirmed that this assessment should be made based on the state of the art at the "time of the trial decision" by the Intellectual Property Trial and Appeal Board (IPTAB).

Crucially, the Court ruled that while the inventive step (non-obviousness) of a patent is assessed based on the prior art existing at the patent's filing date, for the "ease of alteration" under the doctrine of equivalents, "publicly known materials available up to the time of the trial decision (or infringement), even if they emerged after the patent application date," can be considered.

The rationale is that scope confirmation trials are designed for early dispute prevention and resolution, not as the final determination of infringement liability or damages (which occurs in separate civil litigation). Therefore, if a technology becomes publicly known after the patent application but before the trial decision, and it would make the alteration easy for a PHOSITA, this can support a finding of equivalence. This implies that an infringer cannot necessarily escape liability by leveraging newly emerged public knowledge to make a trivial modification.

3. Criteria for Determining "Conscious Exclusion" during Prosecution

The Decision also provided important clarity on how to determine if a specific component or feature was "consciously excluded" from the patent claims during prosecution (prosecution history estoppel, condition 5).

The Supreme Court emphasized that a comprehensive review of the entire prosecution history is required. This includes:

• The specification as filed.
• The examiner's office actions detailing reasons for rejection.
• The applicant's amendments to the claims and arguments made in written opinions.
• The stated reasons for such amendments.
• The applicant's intended technological scope as evidenced by these interactions.

Significantly, the Court stated that merely narrowing the claims during prosecution does not automatically mean that all subject matter surrendered between the broader original claims and the narrower amended claims was "consciously excluded."

Instead, conscious exclusion will only be found if the prosecution history, when viewed holistically, clearly demonstrates "the applicant's unambiguous intent to disclaim or surrender that specific subject matter from the scope of rights," often to distinguish the invention from prior art.

4. Implications and Practical Considerations

This Supreme Court ruling has several practical takeaways for patent practitioners and businesses:

1. Look Beyond Literal Wording: Accused infringers cannot assume safety merely because their product doesn't literally match every element of a patent claim. If the problem-solving principle and effects are substantially similar, and the alteration is easily conceivable based on known technology (even post-filing known technology), equivalence may be found.
2. Consider Current State of Art in Scope Confirmation Trials: When assessing potential equivalence for a scope confirmation trial, parties must consider the technological landscape as it exists at the time of the trial decision, not just at the patent's filing date, for the "ease of alteration" factor.
3. Scrutinize Prosecution History Carefully: The way amendments are made and arguments are presented during patent prosecution can have profound long-term effects on the enforceability of the patent under the doctrine of equivalents. Careless or overly broad disclaimers can inadvertently limit the scope of equivalents.
4. Proactive Strategy for Patent Holders: Patent holders should be aware that potential infringers might attempt to design around patents using minor modifications based on newly emerged public knowledge. They should proactively consider the potential application of the doctrine of equivalents to such modifications.

5. Conclusion

The Supreme Court's 2022Hu10210 Decision provides valuable clarification on the application of the doctrine of equivalents, particularly regarding the timing for assessing the "ease of alteration" and the nuanced approach required for "conscious exclusion." It underscores that a simple claim-narrowing amendment is not, by itself, sufficient to invoke prosecution history estoppel; the applicant's clear intent to disclaim specific subject matter must be evident from the entire prosecution record.

This ruling reinforces the critical importance of strategic prosecution and careful management of the patent application process. Both patent applicants and potential defendants must remain vigilant, closely monitoring the evolving jurisprudence from the Korean Supreme Court on patent scope and infringement to inform their strategies.