Defenses of Defendant

Invalidity Defense

It is well settled that in case the patented invention lacks novelty over the prior art, the patent is unenforceable. Even before the patent has been invalidated through the separate invalidity proceeding, the patent shall be regarded as being void.

As for non-obviousness challenge within an infringement lawsuit under bifurcated system, the Supreme Court has maintained their firm position for a long time that the patent is enforceable before the invalidity based on the ground of being obvious over the prior art. However, the Supreme Court changed their position through en banc decision in 2012. Therefore, a defendant raise an affirmative defense based on obviousness of the patented invention.

The Korean Supreme Court en banc decision in 2012 is that in principle, (1) an issued patent is presumed to be valid; (2) an infringement court may not decide the validity of a patent; (3) arguing invalidity of a patent in suit shall not be a defense in an infringement action; but, as detour as a practical solution, (4) in case the patent in suit is clearly to be invalid due to lack of inventive step as well as lack of novelty, it is an abuse of patent right to seek the injunction and damages based on the patent. Therefore, in order to determine such abuse of a patent right, the infringement court may examine the validity of a patent due to lack of inventive step as well as lack of novelty.

As for standard of proof, presumption of validity is not strong. The challenger can meet his burden by preponderance of evidence, not by clear and convincing. For example, obviousness arguments will be in favor of invalidity where there is inevitable combination, no synergistic effect from combination, no unexpected result.

Other Affirmative Defense

An accused infringer may assert that his practice falls in the scope of publicly known technology in which he is entitled to freely use it. Under the Korean patent law, it might be a mirror image of obviousness arguments.

Further, prosecution history estoppel, experimental use, pharmaceutical clinical test, prior user right, intervening right can be used as defense. For instance, the patent right does not extend to acts done for experimental purposes relating to the subject matter of the patented invention. Further, clinical tests for the purpose of KFDA approval of generics does not infringe a patent right. Unlike the U.S. patent law, a declaratory judgment or inequitable conduct before the PTO defense is not available.

Defendant’s Motion Practice: Deposit Cost in Advance

When a plaintiff is a foreigner having neither a residence nor a business office in Korea, a defendant can file a motion that the plaintiff has to deposit the cost of suit in advance. In this situation, a defendant is not required to respond to a plaintiff’s complaint until a plaintiff deposits the estimated cost of the lawsuit. If the foreign party does not deposit by the date the court specifies, the court may dismiss the suit. In the case where the plaintiff is a foreigner and the defendant is a Korean, the Korean defendant usually file this motion to obtain enough time for considering defense and counterclaim. The foreign party may deposit a bond.