WHAT DOES THAT PATENT MEAN, LITERALLY?
Initially the CAFC overturned a long line of its own precedents, to favor a "line" of two cases of debatable significance, according to the dissent of Judge Michel. Thus a per se rule was born that effectively restricted the century-old doctrine of equivalents. That doctrine deals with the injustice that can result from construing the scope of a patent by using only the literal meaning of the written patent claims. In one notable case, the U.S. Supreme Court recognized the viability (although not the inevitability) of using the doctrine when a patent claimed a process performed at a pH of 6.0 to 9.0, while an accused infringer operated at a pH of 5.0.
There the Court explained that equivalents could be identified using any of a variety of tests. Significantly, the Court held that equivalents are not found by considering a claim as a whole, because no "element" of the claim can be eliminated. Thus, claims are not deemed broadened under the doctrine simply by an element by element substitution of equivalents. Each element of the claim is to be construed as "an X or its equivalent." This rule preserved, at least in theory, the important function of notifying the public of the scope of the patent.
The CAFC restricted the doctrine of equivalents by expanding file history estoppel. That estoppel prevents a patent owner from recovering subject matter actually relinquished in proceedings before the Patent Office. The new estoppel bar would no longer be "flexible," but would rigidly and automatically preclude the doctrine on any element of a claim that was narrowed to obtain a patent.
Amendment of claims is the most important and routine transaction in the Patent Office before a patent is issued. Claims are often amended for substan tive reasons (e.g., avoiding prior art);or form (e.g., improving syntax, correctly translating a foreign word, etc.). The CAFCs per se estoppel made all claim amendments rather hazardous. In his dissent to the CAFC decision, Judge Michel saw a fail-safe method for a copyist to avoid liability for patent infringement: Copy everything but "substitute any known interchangeable structure, matter, or step for any limitation that has been amended ... , no matter how unimportant and insubstantial" the substitution.
The Justices unanimously vacated the judgment of the CAFC and found it had "ignored the guidance of [earlier Supreme Court precedents], which instructed that courts must be cautious before adopting changes that disrupt the settled expectations of the inventing community." The Justices then held that courts must examine and fairly interpret the subject matter surrendered by a narrowing amendment. The doctrine of equivalents would not be precluded for aspects of the invention having "only a peripheral relation to the reason the amendment was submitted." The examination of such "reasons" would undoubtedly ignore intent and implement the "objective inquiry on an element by element basis." In Festo the high Court further refined this objective inquiry. Now, the patentee must show that "one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent."
Two grounds for avoiding file history estoppel were identified, but for limited circumstances: Estoppel is avoided when the equivalents were unforeseeable or inexpressible in words, unless a pre-amendment claim covered the allegedly unforeseen or inexpressible subject matter. Also, the estoppel was declared available for narrowing amendments required for the sometimes formal requirements of 35 U.S.C. §112, not just for amendments required to avoid prior art.
In the end there is still much uncertainty over the reach of the doctrine of equivalents, but perhaps that is how it should be.