Federal Circuit Invalidates Poultry Patent for Indefiniteness of Term “About”

Patent applicants and holders who use approximation terms in their claims, like “about,” should take note of a recent Federal Circuit decision that underscores the risks of imprecise and inconsistent usage of such terms. In Enviro Tech Chemical Services Inc. v. Safe Foods Corp., the Federal Circuit Court of Appeals affirmed the district court’s claim construction invalidating certain claims of U.S. Patent No. 10,912,321 (the ’321 patent) as indefinite under 35 U.S.C. § 112(b).

The patent claimed methods of treating poultry carcasses with peracetic acid and required adjusting the antimicrobial solution to a “pH of about 7.6 to about 10 by adding an alkaline source.”

The court held that while approximation terms such as “about” and “approximately” could be used appropriately to “avoid a strict numerical boundary to the specified parameter,” the range must be “reasonably certain” based on the “technological facts of the particular case” to avoid indefiniteness. Here, the court upheld the district court’s indefiniteness determination, finding that the lack of clarity in the specification and file history contradicted Enviro Tech’s argument that the term “about” was properly limited to mean less than or equal to a variation of 0.3 pH units of the target pH.

The court first noted that the experiments disclosed in the specification contradicted Enviro Tech’s proposed variation of 0.3 pH units of the target pH. Enviro Tech had disclosed numerous experiments in which it set a target pH, measured the pH, and then proceeded depending on the difference between the two. In most instances, Enviro Tech proceeded only when the difference was less than or equal to 0.3 pH units of the target pH. However, in several instances, Enviro Tech proceeded even with deviations between 0.35 and 0.5 pH units of the target pH. The court held that this “conflicting guidance … [did] not allow a skilled artisan to determine the scope of ‘about’ with reasonable certainty.”

The prosecution history also failed to provide sufficient guidance where Enviro Tech’s treatment of the term “about” was inconsistent during patent prosecution. In one office action response, Enviro Tech argued that “a peracetic acid solution at the lower end of the claimed range, pH 7.6,” would not have been obvious over the prior art, but did not address the term “about” with regard to the prior art. However, in another section of the same office action, Enviro Tech addressed the term “about” when discussing pH in the range of about 8 to about 9. The inconsistent treatment of the term “about” suggested that it was material to some claims, while not material to others, which failed to provide notice to a skilled artisan as to the scope of the claim.

The court also rejected Enviro Tech’s argument that it surrendered claim scope during prosecution when it amended the lower boundary of its claimed range from a pH of “about 7.3” to “about 7.6,” thereby disclaiming any pH deviation greater than 0.3 pH units of the target pH. The court disagreed, holding that there was no record of “repeated and consistent remarks during prosecution that can define a claim term,” and the amendment was not “accompanied by explanatory remarks” establishing that “about” meant less than or equal to 0.3 variability in pH. This last element was important because the prior art disclosed a pH of 7.0, which the court noted could be “about” a pH of 7.6.

Takeaways

While this decision does not change the law on indefiniteness, or the appropriateness of using claim terms such as “about” and “approximately,” the court’s holding shows that context is important. The decision highlights important considerations when using approximation claim terms:

• Consistency in disclosures regarding permissible ranges. The specification and prosecution history had numerous inconsistencies as to the scope of “about” and its importance in defining the scope of the claim. Such inconsistencies may suggest a lack of notice to the skilled artisan as to the scope of the claim term, and support a finding of indefiniteness.
• Inclusion of clear explanatory remarks defining the scope of the claim term. Although Enviro Tech pointed to various elements in the file history that potentially supported its proposed construction, such disjointed statements were inadequate to provide the level of clarity required by the court. This suggests that while the court would permit approximation claims, vagueness as to scope could invalidate such patents.
• Potential overlap with prior art. Here, a key element appeared to be the proximity between the pH range claimed in the patent and that disclosed by the prior art. Where the ranges were close enough to allow the claimed lower pH limit to be “about” the same as the prior art pH, the court required greater clarity in defining the scope of the term.

In sum, Enviro Tech serves as a reminder of the importance of maintaining precision and consistency in disclosures about the scope of approximation claim terms, and clarity in establishing the scope of the term during prosecution.