Yesterday, the US Supreme Court wrapped up oral arguments for Microsoft Corporation v. i4i Limited Partnership, in which i4i sued Microsoft for patent infringement. This case has attracted worldwide attention, not only because the infringing product (MS Word) is widely used, but also because the Supreme Court’s ruling will determine the evidentiary standard to which the validity of all US patents will be determined in the future.

Under 35 U.S.C. § 282, an issued patent is presumed to be valid (in other words, it’s assumed to be novel and non-obvious).  Since the 1980s, the Court of Appeal has held that this presumption of validity may only be rebutted with evidence meeting a “clear and convincing” standard.

Microsoft, having lost at the trial level and at the Court of Appeal, argues that the “clear and convincing” standard is too high and that the correct standard should be the lower “preponderance of evidence” standard.  Microsoft argues that the requirement for “clear and convincing” evidence was a requirement made solely by the Court of Appeal and was not the intent of Congress.

i4i, as the patent holder in this case, argues that maintaining the “clear and convincing” standard is necessary for protecting American innovation and inventors, and that Congress had implicitly endorsed the “clear and convincing” standard forwarded by the Court of Appeal by not enacting a law saying otherwise.

As an added twist, the specific evidence that Microsoft now seeks to introduce in order to argue that i4i’s patent is invalid was not previously considered by the US Patent Office during the prosecution of the patent application.  Thus, the Supreme Court may end up treating evidence previously considered by the US Patent Office differently than evidence not previously seen by the US Patent Office.

Despite the rhetoric about protecting American innovation, I think a certain amount of deference is due if the evidence introduced was already considered by the Patent Office during prosecution.  In my view, the higher “clear and convincing” standard should apply to evidence previously considered during prosecution, while the lower “preponderance of evidence” standard should apply for evidence not previously considered by the Patent Office.

A decision is expected from the US Supreme Court before the end of June 2011. Chief Justice Roberts recused himself, so the case will be decided by the remaining eight justices.  If the Supreme Court splits 4-4 then the “clear and convincing” evidentiary standard stands.