On July 31, 2012, in 01 Communique Lab., Inc. v. LogMeIn, Inc., the U.S. Court of Appeals for the Federal Circuit (Rader, Wallach, Fogel*) vacated and remanded the district court's summary judgment that LogMeIn did not infringe U.S. Patent No. 6,928,479, which related to technology that enables one computer to access another computer remotely via the Internet. The Federal Circuit stated:

The locator server computer "includes" software, referred to in the patent as a "location facility," that inter alia locates the personal computer. [The crux of the appeal is] whether the location facility must be contained entirely on a single locator server computer as held by the district court and asserted by LogMeIn, or whether it may be distributed among multiple locator server computers as asserted by 01 Communique. LogMeIn argues that the district court's construction is supported by the fact that the claims refer to the locator server computer in the singular. It points to language such as the following: "a locator server computer linked to the Internet, its location on the Internet being defined by a static IP address." LogMeIn asserts that "because 'its' and 'the' are singular terms, the claimed 'location facility' must be a software component that is included within a single locator server computer."

LogMeIn's argument is at odds with our well-established precedent. "As a general rule, the words 'a' or 'an' in a patent claim carry the meaning of 'one or more.'" "The exceptions to this rule are extremely limited: a patentee must evince a clear intent to limit 'a' or 'an' to 'one.'" "The subsequent use of definite articles 'the' or 'said' in a claim to refer back to the same claim term does not change the general plural rule, but simply reinvokes that non-singular meaning." An exception to the general rule arises only "where the language of the claims themselves, the specification, or the prosecution history necessitate a departure from the rule."

Here, nothing in the claim language or the specification compels a departure from the general rule. The patent's use of words such as "a," "its," and "the" in the claims is insufficient to limit the meaning of "locator server computer" to a single physical computer. LogMeIn claims that such a limitation is supported by the specification, noting that some figures show the location facility 6 as part of a single locator server computer 12. However, the fact that a locator server computer is represented by a single box in some of the figures does not "necessitate" a departure from the general rule that "a" locator server computer may mean "one or more" locator server computers. More to the point, the specification also discloses expressly that "Server Computer 12 may comprise one or more computers, as is well known."

LogMeIn contends that this language is not sufficiently particular to show how the location facility would operate on more than one computer. The specification discloses that "a number of computer program facilities are described in this invention as separate facilities for the sake of describing the invention. However, it should be understood that . . . such facilities can be sub-divided into separate facilities." Read together, the disclosures that facilities may be subdivided and that the locator server computer may comprise multiple computers support a construction that the location facility may be distributed among multiple physical computers. Even if we were to conclude that the specification is ambiguous on this point, such ambiguity hardly is evidence of the clear intent necessary to overcome the effect of the general rule of claim construction applicable here.

"When the patentee makes clear and unmistakable prosecution arguments limiting the meaning of a claim term in order to overcome a rejection, the courts limit the relevant claim term to exclude the disclaimed matter." "A patentee's statements during reexamination can be considered during claim construction, in keeping with the doctrine of prosecution disclaimer." "An ambiguous disclaimer, however, does not advance the patent's notice function or justify public reliance, and the court will not use it to limit a claim term's ordinary meaning." "There is no 'clear and unmistakable' disclaimer if a prosecution argument is subject to more than one reasonable interpretation, one of which is consistent with a proffered meaning of the disputed term."

In 2007, third party Citrix Systems ("Citrix") requested inter partes reexamination of the '479 Patent. On reexamination, the U.S. Patent and Trademark Office initially rejected all of the patent's claims as unpatentable over prior art, but on July 6, 2010, it issued a Right of Appeal Notice withdrawing the rejections as to the particular claims at issue here. The district court concluded that "[d]uring the reexamination of the '479 Patent, 01 clearly and ambiguously [sic] disclaimed having more than one device perform the functions of the location facility." It appears that the district court understood this to mean that 01 Communique disclaimed a system, method, or product in which the location facility is distributed among multiple locator server computers. This conclusion is not supported by the record.

The district court found that LogMeIn's accused products use multiple server computers, and that no single one of those computers performs all of the functions of the location facility. It therefore concluded that LogMeIn's products could not infringe the '479 patent under its claim construction, which required that the location facility be contained on a single computer. Because the district court's ruling was based upon an erroneous claim construction, we vacate the summary judgment of noninfringement.