Standard of Proof in Patent Invalidity cases

Recent litigation going on between Microsoft and i4i corp in Supreme Court can bring a drastic change in way the patent is invalidated in US courts. In US, standard of proof in all civil cases is prepoderance of probabilities. But, in cases challenging the validity of patents, a little more stringent standard "clear and convincing evidence" is used. It is nowhere written in 35 USC that courts must employ a higher standard in patent cases. But over the period of time Federal Courts in US have employed this standard by interpreting 35 USC 282 which says that a presumption of validity will exist in all patents issued by USPTO.

In the present cases, Microsoft is trying to invalidate a i4i patent by arguing that the invention was already on sale before the patent application was filed.

Microsoft's argument is that when a prior art is not considered by PTO then there is no point in employing the clear and convincing evidence standard.

Arguments are over before the Supreme Court and decision is pending. U can listen to the arguments by clicking on the link pasted above.