Evidentiary Standard to Invalidate a Patent

In Microsoft Corp. v. i4i Limited Partnership, the United States Supreme Court considered the standard that should be applied in weighing evidence relied upon to challenge the validity of a United States patent in court proceedings. It concluded that the challenger bore the burden of showing that the facts it relied upon had been established by clear and convincing evidence.

The United States legal system recognizes three different standards of proof that may be required in different situations. In criminal proceedings it is normally required that the prosecution establishes the guilt of the accused beyond a reasonable doubt. In most civil proceedings, however, the requirement is simply for the party asserting a particular fact to establish that it is true by a preponderance of the evidence (that is that is is more likely than not that the fact asserted is true). There are, however, situations in civil proceedings where the courts recognize that something more than the mere likelihood that an asserted fact is true is necessary before the court can rely on it. In such circumstances the part asserting the truth of a fact must convince the judge or jury as the case may be that it is highly probable that the fact in question is true.

35 USC 282 states:

A patent shall be presumed valid. Each claim of a patent (whether in independent, dependent, or multiple dependent form) shall be presumed valid independently of the validity of other claims; dependent or multiple dependent claims shall be presumed valid even though dependent upon an invalid claim. … The burden of establishing invalidity of a patent or any claim thereof shall rest on the party asserting such invalidity.

Since its inception in 1982, the Court of Appeals for the Federal Circuit has read this provision as requiring that for a party challenging the validity of a granted patent in proceedings before a court to succeed it bore the burden of producing clear and convincing evidence to support of its factual assertions. Microsoft contended that this interpretation was incorrect.

i4i sued Microsoft for infringement of a patent claiming a method for editing computer documents. It was agreed that i4i had sold a software product more than one year prior to the filing date of the application giving rise to the patent. It therefore needed to be determined whether that software product embodied the invention claimed in the patent. The code was no longer available and so the court had to consider evidence from witnesses relying on their recollection of the nature of the product that had been sold. The jury was instructed that to find that the software did fall within the scope of the claims clear and convincing evidence of this was required. The jury was not convinced. Microsoft appealed. The Federal Circuit Court of Appeals found no error in the jury instructions.

Against a background of criticism of the use of the clear and convincing evidence standard in patent validity disputes in government reports and elsewhere, the Unites States Supreme Court granted certiorari to consider the question of whether “the court of appeals erred in holding that Microsoft’s invalidity defense must be proved by clear and convincing evidence.”

The Supreme Court held that the Court of Appeals had not erred. Justice Sotomayor giving a judgement in which six of her colleagues agreed held that the language of 35 USC 282 quoted above had been a codification of the common law and as such should be construed in a way consistent with pre codification case law on the subject. This case law had for one hundred years required clear evidence going beyond the balance of probabilities for a court to find a patent invalid. The statute should therefore be read in the same way. Microsoft had argued that even if such a rule applied where the facts in dispute had been considered by the Patent Office, it should not apply in cases such as the present where the facts in issue had never been considered by the Patent Office. Sotomayor J disagreed, pointing out that the Supreme Court had prior to the codification “often applied the heightened standard of proof without any mention of whether any relevant prior art evidence had been before the PTO examiner:”. She went on:

Nothing in §282’s text suggests that Congress meant to depart from that understanding to enact a standard of proof that would rise and fall with the facts of each case. Indeed, had Congress intended to drop the heightened standard of proof where the evidence before the jury varied from that before the PTO – and this take the unusual and impractical step of enacting a variable standard of proof that must be adjudicated in each case- we assume it would have said so expressly.

She did, however, recognize that appropriate jury instructions might differ depending on whether the facts in issue had been considered by the PTO in the following words:

Simply put, if the PTO did not have all material facts before it, its considered judgment may lose significant force. And, concomitantly, the challenger’s burden to persuade the jury of its invalidity defense by clear and convincing evidence may be easier to sustain. In this respect, although we have no occasion to endorse any particular formulation, we note that a jury instruction on the effect of new evidence can, and when requested, most often should be given. When it is disputed whether the evidence presented to the jury differs from that evaluated by the PTO, the jury may be instructed to consider that question. In either case, the jury may be instructed to evaluate whether evidence before it is materially new, and if so, to consider that fact when determining whether an invalidity defense has been proved by clear and convincing evidence.

Unfortunately for Microsoft, it had not requested such a jury instruction in the present case.

Justice Breyer, with whom Justices Scalia and Alito agreed, while concurring in the decision in full, added the observation that

Many claims of invalidity rest … not upon factual disputes, but on how the law applies to facts as given. Do the given facts show that the product was previously in public use? Do they show that the product was novel and that it was non-obvious? Do they show that the patent applicant described his claims properly? Where the ultimate question of patent validity turns on the answer to legal questions … today’s strict standard of proof has no application. (Internal citations omitted)

Justice Thomas concurred in the judgment of the majority, but for a different reason. He did not see 35 USC 282 as a codifying the common law standard, but agreed that Congress had intended to adopt the “clear and convincing” standard.

Chief Justice Roberts did not participate in the case.