In August, the Federal Circuit decided Arendi S.A.R.L. v. Apple Inc., in which the Court ruled that the Patent Trial and Appeal Board misapplied the law on permissible use of common sense in an obviousness analysis. In reversing the PTAB’s final decision, the Federal Circuit held that the PTAB’s application of common sense to supply a limitation missing from a prior art reference was conclusory and unsupported by substantial evidence. In its decision, the Federal Circuit clarified the proper use of common sense in an obviousness finding—helpful guidance for practitioners in what is otherwise a murky, intuitive area.


In response to being sued in district court by Arendi for infringement of U.S. Patent 7,917,843, appellees Apple, Google, and Motorola Mobility filed a petition for inter partes review of the asserted claims. The district court proceedings were then stayed pending completion of the inter partes review proceeding.

The claims of the ’843 patent are generally directed to techniques for locating information in a displayed document using a first computer program and, using a second computer program, retrieving from an external source information related to the located information. Petitioners maintained that a single prior art reference—Pandit —rendered the claims obvious.

Pandit discloses methods for recognizing predetermined types of text in a body of text and performing operations relevant to the recognized text. In the specific embodiment of Pandit cited by Petitioners, the recognized text is a telephone number and the operation performed is adding the recognized telephone number to an address book. Petitioners maintained that Pandit taught each and every limitation of claim 1 of the ’843 patent but one—that of searching for related information using the located information (i.e., a telephone number) as a search key. The PTAB, however, agreed with Petitioners that, as a matter of common sense, the technique disclosed in Pandit can be presumed to perform a search of the address book using the identified telephone number in order to avoid duplicate telephone number entries.

The Proper Application of “Common Sense”

The Respondents appealed. As a threshold matter, the Federal Circuit reaffirmed that common sense and common knowledge can play a role in the obviousness inquiry. However, the Federal Circuit cautioned that the application of common sense to an obviousness analysis is subject to constraints.

First, the Federal Circuit observed that common sense is typically invoked to provide a motivation to combine prior art references, rather than to supply a missing claim limitation. Second, on those occasions where common sense is invoked to supply a missing limitation—as the PTAB did in this case—the Federal Circuit explained the limitation at issue should be simple and peripheral, where the underlying technology is straightforward. By contrast, the Federal Circuit expressed great skepticism over the application of common sense to those limitations that play a central role with respect to the claimed subject matter. Finally, whether common sense is invoked to supply a motivation to combine or to supply a missing claim limitation, the Federal Circuit instructed that references to common sense should not be used as a substitute for evidentiary support and reasoned analysis. This is especially true in cases where common sense is invoked to supply a missing limitation that goes directly to the heart of the invention.

Because the patent at issue relates primarily to the retrieval of data from an information source based on content of a document, the disputed search step was found to be central to the claimed subject matter, rather than merely a peripheral limitation. Thus, Appellees were required to meet a relatively high standard for invoking common sense to supply the missing limitation.

Although Appellees argued that the process of searching for data in a database was well known at the time of the invention, Appellees failed to provide any reason why it would be proper to extrapolate from this general knowledge to specifically add a telephone number search to the Pandit reference. Similarly, the Federal Circuit also found testimony from Appellees’ expert witness unavailing because it failed to specifically demonstrate how using a telephone number to search the address book of Pandit would have been effective for preventing duplicate entries. In sum, the Appellees’ conclusory statements and unspecific expert testimony were insufficient to invoke common sense to supply this key limitation.

Practical Guidance

The Federal Circuit’s opinion here provides guidance regarding the application of common sense in an obviousness analysis, both for patent prosecution lawyers and patent litigators.

On the patent prosecution front, an applicant confronting an obviousness rejected based in part on common sense can use this case as leverage and press the patent examiner to explain, specifically, and with evidentiary support, why a given limitation absent from the prior art would have been obvious based on the common sense of one of ordinary skill. A mere broad and passing reference to common sense should not suffice, and could even set up grounds for an appeal of that rejection. Further, in cases in which there may be a wealth of background knowledge that generally relates to a missing limitation, it is still incumbent on the examiner to “bridge the gap” between this general knowledge and the specific requirements of the claims.

For patent litigators, the decision is a helpful guide for parties on both sides of an invalidity case. A party seeking to invalidate a patent based on part on common sense will need to support its case with more than just conclusory testimony from a technical expert; rather, specific and supported expert testimony will be required. In the event that testimony is not offered by a patent challenger, the patentee may be able to undermine the invalidity challenge on that basis.