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Standard Of Proof For Patent Invalidation In The U.S. And Japan, Yoshinari Oyama

Yoshinari Oyama

In June 2011, the U.S. Supreme Court confirmed the standard of proof for patent invalidation in Microsoft Corp. v. i4i Limited Partnership, et al. The Court held that an invalidity defense to be proven by clear and convincing evidence rather than by a preponderance of the evidence and that burden is constant and never changes. Compared to the U.S. patent system, there is no heightened standard of proof required for patent invalidation in infringement suits in Japanese courts and the invalidation rate is high especially after Kilby cas in 2000, where the Japanese Supreme Court decided that a patentee could …