Assuming novelty, the USPTO, PTAB, or a court must establish that the claimed invention would have been obvious over the prior art. In other words, even though the prior art does not identically disclose or describe the invention, one may not obtain a patent on the invention if the differences between the invention and the prior art are such that the invention as a whole would have been obvious to the person of ordinary skill in the pertinent art at the pertinent time. 35 U.S.C. §103. 35 U.S.C. §102 (both pre- AIA §102 and AIA §102) defines the prior art that can be used to invalidate a patent for obviousness under §103. AIA §102, and its definitions of prior art, went into effect March 16, 2013.
Pre-AIA, the relevant time period for evaluating what the person skilled in the pertinent art would have considered to have been obvious is just prior to when the invention was made. Under AIA 35 U.S.C. §103, effective March 16, 2013, the relevant time period is “before the effective filing date of the claimed invention.”
In crafting arguments of nonobviousness during prosecution, it is useful to cite both the MPEP, the examination handbook of the examining corps, as well as the case law. The case law will provide valuable support if the claims issue and are then challenged before the Patent Trial and Appeal Board (PTAB) or the district courts. By having footnoted the case law during prosecution, the case law will not appear to be an afterthought.