Corpus linguistics is a relatively new and untested tool in the realm of statutory interpretation. While the overall use of corpora is not new, its first appearance in a Supreme Court case was in 2011.1 In a nutshell, corpus linguistics is “the study of language function and use by means of large, principled collections of naturally occurring language called corpora.”2 Corpora are “large collection[s] of naturally occurring texts that are sampled to be representative of a particular type of language . . .”3
Essentially, there are two types of corpora: general and specialized; “[s]pecialized corpora are typically smaller [than general corpora] and focus on a more specific or less accessible variety of language.”4 Both general and specific corpora can be compiled in many different ways. For instance, corpora can be diachronic or synchronic. Synchronic corpora, in particular, “include texts from a single time period, allowing for closer comparisons of language varieties within a time frame.”5 Therefore, it is possible to create (and they may already exist) corpora from different technical industries within specific time periods.
The Federal Circuit’s and the federal district courts’ patent claim construction standard was stated in Phillips v. AWH.6 In determining the meaning of words in a patent claim, the Federal Circuit will first look at the following intrinsic evidence, in order of importance: the claim language itself, the specification of the patent, and the prosecution history for the patent.7 The words within a claim are evaluated by a “person of ordinary skill in the art in question” on the effective filing date of the patent application.8 This means that terms are generally given their customary meaning within a field, as supported by their use in other claims and by the context provided by the patent’s specification and prosecution history.9 The patent’s specification, in particular, is “[u]sually . . . dispositive; it is the single best guide to the meaning of a disputed term.”10 If terms are still ambiguous after looking at intrinsic evidence, the court will turn to the following extrinsic evidence, in order of importance: technical dictionaries and treatises, general dictionaries, and expert testimony.11 However, extrinsic evidence cannot be used to contradict intrinsic evidence.12 Finally, if a court, after using all of the above tools, still finds that a claim is ambiguous, then the court should generally construe the claim to preserve its validity.13
There is an argument that corpus linguistics would be helpful for judges in determining the meaning of claim terms through the lens of a person having ordinary skill in the art on the effective filing date of the patent application. For instance, a corpus can operate as a stand-in for a person having ordinary skill in the art. As stated above, a sufficiently specific synchronic corpus represents the collection of language used within that specific genre and timeframe. Thus, the corpus provides the customary meaning of terms within that genre and timeframe, which is exactly what the courts are looking for under the Phillips claim construction standard.
Yet, despite the clear advantage in using corpus linguistics for claim construction, there are notable limitations. For example, we should consider whether and when judges may use this tool in the realm of claim construction. Judges could use corpora as extrinsic evidence, which may not be considered unless the terms are still ambiguous after considering all of the intrinsic evidence. At that point, corpus linguistics is no more than one tool among many at the disposal of the court as extrinsic evidence. Even if corpus linguistics is considered as intrinsic evidence, courts may be slow to adopt it. As noted earlier, corpus linguistics is still considered a new for statutory interpretation, despite the Supreme Court finding it persuasive in 2011.
Finally, we should also be aware of the practical limitation of corpora themselves. Even if the general idea of using corpus linguistics is persuasive to judges, they may find that there is not a sufficiently specific corpora in the subject matter at issue to be useful as a stand-in for the person having ordinary skill in the art. In these situations, corpus linguistics would not assist judges in construing patent claims.
Corpus linguistics has recently been acknowledged by the Supreme Court as a helpful tool that judges may use in cases involving statutory interpretation. While untested, there seem to be clear advantages to using corpus linguistics for patent claim construction under the Phillips standard. Nonetheless, as with any new practice, there are several considerations that should be further explored before applying this tool to an established methodology.