The phrase "at least one of" is commonly used in patent claims, but its interpretation is subjective and has led to some controversy. The issue that arises is this: when the phrase in its entirety is "at least one of A, B and C", should it be understood as at least one of A AND at least one of B AND at least one of C, or should it be understood as at least one of A OR B OR C. In other words, the central question is whether the phrase should be understood in the conjunctive or the disjunctive form.
Although Indian Courts have not dealt with this issue, the Indian Patent Office has tended to object to claims that use the phrase "at least one of" on the ground that it enlarges the scope of the claims and makes them indefinite. For example, certain claims in a patent application1 that described a taste modifying sweetener composition and method of making the same were objected to under Section 10(5) of the Indian Patents Act, 1970 on the ground that phrases like "at least one" makes the claims too broad, vague and unclear.
SuperGuide v. DirecTV: "at least one of" in the conjunctive
Unlike India, Courts in the United States of America have discussed this issue directly in multiple cases. One of the most prominent of these was the decision of the US Court of Appeals for the Federal Circuit in SuperGuide Corp. v. DirecTV Enters., Inc.2 Here, the Court interpreted the phrase "at least one of" in the conjunctive.
The plaintiff, SuperGuide, asserted three different patents against multiple multimedia providers, one of which was DirecTV. One of these patents described an online television program schedule system. SuperGuide had filed for infringement against DirecTV and a key dispute was about claim construction involving the phrase "at least one of." Claim 1 of the patent read, "First means for storing at least one of a desired program start time, a desired program end time, a desired program service, and a desired program time."
SuperGuide asserted that this phrase should be interpreted in the disjunctive, since according to them, it meant one or more of the four listed criteria in the claim. However, DirecTV argued that the correct interpretation of the phrase would be in the conjunctive, which meant that it should refer to at least one start time, at least one end time, at least one service channel AND at least one type.
The Courts agreed with DirecTV. The District Court held that the term "a desired" was repeated for every category that had been listed, and therefore it must be read in the conjunctive. Further, they held that if the phrase were to refer to only one category, it would contradict the fundamental purpose of the invention as described. The Court of Appeals also affirmed the opinion of the District Court and interpreted the phrase as one value for each category.
Post SuperGuide: "at least one of" may sometimes also be in the disjunctive
Although various US courts have since upheld the decision in SuperGuide, some have also distinguished the same, pointing out that the conjunctive meaning of "at least one of A, B and C" would not apply when a patent claim, specification, or the prosecution history necessitates a meaning that is wider in scope.
In such cases, US courts and tribunals have applied a disjunctive interpretation. An example of this can be found in Fujifilm Corp. v. Motorola Mobility3 where Fujifilm had accused Motorola of infringing certain claims of their existing patent. One disputed issue was the interpretation of the claim "wherein said display includes a menu comprising selections for at least one of a transmit image mode for transmitting an image from the wireless telephone to an apparatus, a receive mail mode for receiving characters, and a transmit mail mode for transmitting characters."
Motorola relied on the holding in SuperGuide, i.e., the phrase "at least one of" must be construed conjunctively. Fujifilm argued that "the plain and ordinary meaning of this phrase was" one or more of the following. The District Court agreed with Fujifilm's argument, holding that the modes of operation listed in the menu comprising limitation are not categories that are comprised of various possible values that the users must choose at least one from every category, for the purpose of the invention to be served. Therefore, the phrase "at least one of" was read disjunctively.
Another case that distinguished SuperGuide was that of Ex parte Concha,4 where, too, the phrase "at least one of" was read disjunctively. Here, it was held that the claims and specification suggested that only a single item should be selected, rather than a plurality of the items.
Courts have not swung entirely away from SuperGuide, though, and there are still cases where a conjunctive interpretation has been upheld. An example of this is the case of Ex parte Gardner.5 Here, the panel concluded that providing at least one of a "data sources portion" and a "processes portion" required providing access to both, a "processes portion" as well as a "data sources portion." In other words, not merely one of the two, but both were required.
In Ex parte Jung,6 the US Patent Trial and Appeal Board (PTAB), while following SuperGuide, held that it is important to consider the specification as well as the prosecution history to find the plain meaning and intention of the claim. The PTAB interpreted the phrase "at least one of" conjunctively and overturned the prior art rejection. However, the PTAB went on to refuse the application for a lack of written description. Although this decision was originally designated as informative by the US Patent and Trademark Office (USPTO), it was subsequently de-designated on the ground that it had been misunderstood.
There is still clearly a lot of fog around the interpretation of the phrase "at least one of", which means that patent drafters need to exercise caution in using this phrase in patent specifications. While the use of "at least one of" along with "and" for reciting a plurality of claim elements is generally read conjunctively, it is important to ensure that this interpretation is consistent with the written description, and is in fact the claim protection that is sought. If a disjunctive meaning is intended, then the phrase must be used along with the connector "or" to define alternatives. The specification as well as prosecution history, in its entirety, also assume relevance when interpreting this phrase. If the draft is unclear in any of these respects, there is a possibility that a list intended to be read in the conjunctive might end up being interpreted in the disjunctive and vice versa.
1 Application No. 7884/CHENP/2010.
2 SuperGuide Corp. v. DirecTV Enters., Inc., 358 F.3d 870 (Fed. Cir. 2004).
3 Fujifilm Corp. v. Motorola Mobility LLC, No. 12-CV-03587-WHO, 2015 WL 1265009 AT *8 (N.D. Cal. Mar. 19, 2015).
4 Ex parte Concha, No. 2012-008364, 2015 WL 397716 (PTAB Jan. 28, 2015).
5 Ex parte Gardner, No. 2009-010298, 2011 WL 180106 (BPAI Jan. 12, 2011).
5 Ex parte Jung, No. 2016-008290 (PTAB Mar. 22, 2017).
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