Article 163 of the Korean Patent Act (‘Non bis in idem’) relates to double jeopardy, and provides that no person may demand a re-trial based on the same facts and evidence once a trial ruling on the same becomes final and conclusive. In the case of an invalidation trial, for instance, “the same facts and evidence” may refer to the grounds for invalidation (e.g. inventive step) and evidence (e.g. prior art). Accordingly, once a decision on the merits of such a trial (hereafter the ‘earlier trial’) has become final and conclusive, a subsequent trial filed based on the same facts and evidence (the ‘later trial’) is not permissible.

Invalidation trials in Korea are inter partes actions, but as a ruling on validity/invalidity has a general effect, the manner in which double jeopardy is applied is important. In particular, the point in time at which it is determined whether there is an earlier final and conclusive judgement on the merits in an earlier trial and the point in time at which it is determined whether “the same facts and evidence” exist with respect to a later trial can be problematic.

Before, the existence of an earlier final and conclusive trial ruling was determined at the time of ruling in a later trial. However, this was changed according to a January 19, 2012 en banc Supreme Court decision (case 2009Hu2234), following which the timing of such determination was brought forward to when the later trial is filed. Based on this, if the ruling in an earlier trial only became final and conclusive after the later trial had been filed, the provisions relating to double jeopardy would not apply.

On April 9, 2020 another Supreme Court decision relating to the timing for determining the existence of “the same facts and evidence” was handed down (case 2018Hu11360). This decision clarifies that for patent invalidation trials, the point in time at which it is determined whether the “same facts and evidence” exist in an earlier trial is when the trial decision is issued by the Intellectual Property Trial and Appeal Board (IPTAB) in the later trial.

The history of this recent case is as follows: an invalidation action filed by Party C concerning Party B’s registered patent was dismissed (i.e. the patent was deemed to be valid) and such decision became final and conclusive; Party A subsequently filed an invalidation action based on the same facts and evidence, and the IPTAB dismissed the action based on double jeopardy; Party A then appealed this decision to the Korean Patent Court and raised a new ground for invalidation which was not dealt with in the earlier instance; the appeal was dismissed by the Patent Court, and Party A further appealed up to the Supreme Court.

In dismissing Party A’s appeal, the Supreme Court ruled that “when determining if the provisions of double jeopardy apply, the IPTAB must consider all of the amended facts and evidence from the time the trial was filed until the time of ruling and, on the basis of the time of ruling, determine whether the filed trial is based on the same facts and evidence as an earlier final and conclusive ruling”, going on to conclude that “the trial-requesting party is not permitted to present new grounds for invalidation [in a Patent Court action] which were not dealt with during the trial”.

In short, when making a determination on double jeopardy, the existence of an earlier final and conclusive trial ruling is determined at the time of filing of a later trial, and whether the case relates to the same facts and evidence is determined at the time of ruling in the later trial.

Practically speaking this means that before a ruling in an earlier invalidation trial becomes final and conclusive, a third party may file a separate invalidation trial based on the same facts and evidence, and during the course of this separate trial may present new invalidation grounds or evidence (e.g. new prior art) in the knowledge that when the determination is made as to whether the facts and evidence in the two trials are the same — i.e. at the time of ruling of the later trial — if the facts and evidence have since become different, the matter will not be deemed to fall within the definition of double jeopardy.