CAFC Says ‘Words of Approximation’ in Patent Claims Must Be Sufficiently Explained to Avoid Indefiniteness

The U.S. Court of Appeals for the Federal Circuit (CAFC) on Monday in a precedential decision authored by Judge Lourie affirmed a district court’s ruling determining certain claims of Enviro Tech Chemical Services, Inc.’s patent for a method of poultry treatment indefinite.

Enviro Tech’s U.S. Patent No.10,912,321is titled “Methods of Using Peracetic Acid to Treat Poultry in a Chill Tank During Processing.” Enviro Tech sued Safe Foods Corp. for infringement of a number of claims of the patent in the U.S. District Court for the Eastern District of Arkansas. Safe Foods in turn argued during claim construction that two terms of claim 1—“an antimicrobial amount” and “about”—were indefinite. The district court agreed and thus found all of the asserted claims invalid for indefiniteness.

The relevant portions of Claim 1 refer to “an antimicrobial amount of a solution of peracetic acid” and “a pH of about 7.6 to about 10.” On appeal, Enviro Tech challenged both of the district court’s indefiniteness holdings, but the CAFC reached only the court’s holding that “about” is indefinite.

The district court found that none of the intrinsic evidence informed a skilled artisan what the scope of the term “about” is with “reasonable certainty.” The CAFC explained that “[w]e have long held that words like ‘about’ and ‘approximately’ may be appropriately used to ‘avoid[] a strict numerical boundary to the specified parameter’…. however, the parameter’s range must be reasonably certain based on the ‘technological facts of the particular case.’” In making that determination, the court considers the claims, patent specification, prosecution history and extrinsic evidence. In this case, “the claims do not provide any guidance on how much below a pH of 7.6 or above a pH of 10 the peracetic acid-containing water can be to meet the limitation.”

Turning to the specification, while there were examples provided of various experiments in which a majority of the experiments only proceeded when “the difference of the actual pH was less than or equal to 0.3 of the target pH,” there were deviations from that practice that were significant enough to result in the CAFC’s finding that “[t]he ’321 patent specification’s conflicting guidance thus does not allow a skilled artisan to determine the scope of ‘about’ with reasonable certainty.”

With respect to the prosecution history, Enviro Tech alternately referred to the claimed range as “pH 7.6” and “about 8 to about 9.” The CAFC explained: “At no point in the entire prosecution history does Enviro Tech explain what ‘about’ means. Rather, Enviro Tech treated the term inconsistently, suggesting that it was material to some claims and immaterial to others.”

While Enviro Tech argued that it surrendered claim scope during prosecution by amending the lower boundary of the claimed range from “about 7.3” to “about 7.6” and that “therefore…‘about’ means less than or equal to 0.3,” the CAFC said it was “not convinced.” The opinion said:

“Enviro Tech points to no remarks it made to the examiner that are the sort of ‘repeated and consistent remarks during prosecution [that] can define a claim term,’ nor is Enviro Tech’s ‘amendment accompanied by explanatory remarks’ suggesting that ‘about’ should be construed to mean less than or equal to 0.3 pH.”

In fact, the CAFC said, the amendment was an important factor in the decision, since the claim was amended to avoid the prior art pH of 7.0, yet the specification recites pHs of 6–10. In such a case, “the definiteness requirement of § 112 necessitates much more clarity than using the vague term ‘about.’”

The CAFC thus affirmed the district court’s ruling with respect to its finding that the term “about” is indefinite. Since that finding rendered all of the asserted claims invalid, the appellate court did not need to address the alternative ground that “antimicrobial amount” is indefinite.

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