Clearing up Conjunctive Claim Construction: PTAB Guidance on the Use of “At Least One Of”

The phrase “at least one of” is used in claims to indicate selection from a group of elements that follows the phrase. When used, practitioners may grapple with whether “at least one of A and B” or “at least one of A or B” is appropriate. Recent guidance from the Patent Trial and Appeal Board provides clarity on the issue and may help practitioners claim a particular group of consumer products as intended.

The Board recently designated the 2017 ex parte appeal decision in Ex parte Jung as informative because it discusses issues of claim construction that arise when “at least one of” is used in a claim. Appellants in Jung filed an appeal with the Board after their claims were rejected during prosecution.[1] The claims are directed at methods for playing back a scene using Universal Plug and Play, and the relevant portions of the claims recite “at least one of [first item category] and [second item category].”[2] Appellants argued that their claims should be construed to read “at least one of [first item category] and at least one of [second item category],” which effectively requires a selection of at least one item from each category for a total of at least two items.[3]

The Board agreed with Appellants and held that ordinarily the phrase “at least one of” should be construed to apply to each of the categories of items that follow.[4] The Board based its holding on a Federal Circuit case, Super Guide, that examined a similar issue.[5] In that case, the Federal Circuit held that the ordinary meaning and usage of the phrase “at least one of” is such that it applies to each of the categories that follows.[6] The Board went on to explain, however, that “[a]n Examiner may adopt a different meaning if called for based upon the usual claim construction considerations, including analyzing the specification for any definition or disavowal.” This conclusion, the Board reasoned, followed from dicta in Super Guide and a line of decisions that did not follow Super Guide because of distinguishing factual information present in those cases.[7] The Board noted that in these situations, “like [in] any claim construction straying from ordinary meaning, the Examiner should set forth the reasoning for such an interpretation, including citations and explanations of relevant portions of the claims, specification, or prosecution history.”[8]

Practitioners and applicants should take caution when using the phrase “at least one of”. Ideally, the meaning of the phrase, including where it is intended to mean “at least one from each of the following categories,” should be made explicit in the specification. For example, in Jung, the specification included examples of both usages of “at least one of” (i.e. selecting one or more from each category or selecting one item total), but the Board found that this was not sufficient to overcome the ordinary meaning of the phrase, stating “[a] mere example of ‘or’ in the Specification without more that would compel the disjunctive is insufficient to overcome the ordinary meaning of a claim using the conjunctive ‘and’.”[9] Practitioners and applicants should also consider other claim language that does not use the phrase, such as, for example, a broader genus that includes both A and B.