On August 10, 2016, in Arendi v. Apple et al., the Federal Circuit reversed a final written decision in which the PTAB held that claims were unpatentable as obviousness, finding that the PTAB had improperly relied on common sense to fill a gap in the primary prior art reference.

The court acknowledged that, post-KSR, common sense has a role in the obviousness inquiry, but also spelled out “three caveats … in applying ‘common sense’”: (1) common sense typically provides a motivation to combine and does not fill in missing claim limitations; (2) when common sense is used to fill in a missing limitation, it has always involved “unusually simple” limitations in which the technology is “particularly straightforward”; and (3) in any context, common sense “cannot be used as a wholesale substitute for reasoned analysis and evidentiary support.”

In reversing the PTAB’s finding of obviousness, the Federal Circuit emphasized that common sense should not be used as a substitute for missing claim limitations that “play[] a major role in the subject matter claimed.” The court found that substantial evidence did not support the PTAB’s reliance on common sense to fill an “important limitation” in the claims. The court also noted that “[t]he use of common sense does not require a specific hint or suggestion in a particular reference, only a reasoned explanation that avoids conclusory generalizations.”

Notably, the primary prior art reference here did disclose the missing limitation (as discussed at oral argument), but the PTAB refused to consider that part of the reference because it was not cited in the petition. At oral argument, the panel made a clear distinction between evidence relied on by the Board (can be used as a basis to affirm) and evidence merely in the record (not necessarily helpful to an appellee seeking to establish substantial evidence supporting the PTAB’s final written decision).

The takeaway? Whenever possible, petitioners should (1) include prior art that discloses all challenged claim limitations (unless they are “unusually simple”), (2) carefully cite to all relevant portions of the prior art, and (3) only argue common sense when necessary, and usually only as a reason to combine references.