In Dow Chemical Co. v. Nova Chemicals Corp., the Federal Circuit held claims reciting a limitation that could be calculated in several ways indefinite where the patent claims, specification, and prosecution history failed to indicate which method should be used. For those wondering whether the “reasonable certainty” standard set forth in the Supreme Court’s Nautilus decision will have any real-world impact, this case shows that it can, since the Federal Circuit previously upheld the same claims under the “insolubly ambiguous” standard. 

The Dow Patent Claims At Issue

Claim 6 of U.S. Patent No. 5,847,053 is representative of the claims challenged on indefiniteness grounds:

6.  An ethylene polymer composition comprising

(A) from about 10 percent (by weight of the total composition) to about 95 percent (by weight of the total composition) of at least one homogeneously branched linear ethylene/α-olefin interpolymer having:

(i) a density from about 0.89 grams/cubic centimeter (g/cm³) to about 0.935 g/cm³,

(ii) a molecular weight distribution (M_w/M_n) from about 1.8 to about 2.8,

(iii) a melt index (I₂) from about 0.001 grams/10 minutes (g/10 min) to about 10 g/10 min,

(iv) no high density fraction,

(v) a single melting peak as measured using differential scanning calorimetry, and

(vi) a slope of strain hardening coefficient greater than or equal to 1.3; and

(B) from about 5 percent (by weight of the total composition) to about 90 percent (by weight of the total composition) of at least one heterogeneously branched linear ethylene polymer having a density from about 0.93 g/cm³ to about 0.965 g/cm³.

The Previous Not-Indefinite Decisions

As noted in the Federal Circuit decision, Dow Chemical Company asserted selected claims of U.S. Patent No. 5,847,053 and U.S. Patent No. 6,111,023 against NOVA Chemicals Corporation (Canada) and NOVA Chemicals Inc. (Delaware). A jury found the asserted claims to be infringed and not invalid, and the Federal Circuit affirmed, holding, among other things, “that the asserted claims were not indefinite.” The district court then conducted a bench trial for a supplemental damages period through the expiration date of both patents, granted $30M in supplemental damages in the form of lost profits and reasonable royalties, and denied Dow’s request for enhanced damages. NOVA appealed, and Dow cross-appealed.

In the meantime, the Supreme Court issued its Nautilus decision setting forth the “reasonable certainty” test for definiteness. The Federal Circuit determined that “the intervening change in the law of indefiniteness resulting from Nautilus provides an exception to the doctrine of law of the case or issue preclusion,” and decided that it needed to evaluate the claims under the Nautilus standard in order to review the supplemental damages award.

“slope of strain hardening coefficient”

As explained in the Federal Circuit decision, the “slope of strain hardening coefficient” is a parameter devised by the inventor, and not previously used in the art.  The ’053 patent explained how to calculate this parameter based on the “slope of strain hardening” and the “melt index” of a polymer, and both  “strain hardening” and “melt index” were well known properties of polymer compositions. However, the indefiniteness problem arose because there are at least four different procedures for measuring the slope of the strain hardening, each of which could produce a different value.

The court reviewed the intrinsic record, and determined that none of the claims, specification or prosecution history discussed how to measure slope, provided any guidance as to which method should be used, or even indicated that the four methods in evidence represented all possible methods of determining the slope of the strain hardening.

Applying the Nautilus standard, the Federal Circuit held that existence of multiple methods that could lead to different results and the absence of guidance in the patent or prosecution history as to which method should be used rendered the claims indefinite because they “fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.” The court therefore reversed the $30M supplemental damages award.

Impact Of the Reasonable Certainty Standard

As noted above, the Federal Circuit had previously upheld the same claims because they were not “insolubly ambiguous.” In this decision, the court explained the different standards as follows:

The question is whether the existence of multiple methods leading to different results without guidance in the patent or the prosecution history as to which method should be used renders the claims indefinite. Before Nautilus, a claim was not indefinite if someone skilled in the art could arrive at a method and practice that method. …. In our previous opinion, relying on this standard, we held that the claims were not indefinite, holding that “the mere fact that the slope may be measured in more than one way does not make the claims of the patent invalid.” …. This was so because Dow’s expert Dr. Hsiao, a person skilled in the art, had developed a method for measuring maximum slope. …. Under Nautilus this is no longer sufficient.

The Federal Circuit noted that the facts of this case are “quite similar” to those of Teva Pharm. USA, Inc. v. Sandoz, Inc., where the court held indefinite a claim limitation reciting the “molecular weight” of a polymer, because there were three different ways to determine molecular weight (each of which could yield a different value), the specification did not define molecular weight, and the prosecution history of related patents was inconsistent as to which of the three methods should be used. However, although the court stated in Dow that “the claims here are even more clearly indefinite than those in Teva,” the Teva claims were held indefinite under both the insolubly ambiguous standard and the reasonable certainty standard.

Focusing On Clarity

The Federal Circuit decision in Dow shows that the Nautilus standard can have an impact on claim validity. While the Supreme Court recognized in Nautilus that “the definiteness requirement must take into account the inherent limitations of language,” the willingness of courts to scrutinize the clarity of claims shows that Applicants should take care with their claim language, and be particularly cautious when coining new terms or devising new parameters to define their inventions.