An invention must be non-obvious to qualify for patent protection. However, the analysis to determine obviousness of an invention is anything but simple and straightforward, as hindsight invariably creeps in.

The courts have struggled with finding the right balance in the analysis.  The Supreme Court weighed in with its KSR decision in 2007 and said that a flexible approach was necessary.  In analyzing whether multiple elements from different references can be combined together to show that an invention is obvious, the Court explained that common sense teaches "that familiar items may have obvious uses beyond their primary purposes, and in many cases a person of ordinary skill will be able to fit the teachings of multiple patents together like pieces of a puzzle." This opened the door to simply using "common sense" as a reason to combine features from various references to invalidate patents and reject applications. Unfortunately, many Examiners and defendants used this new "common sense" tool as a shortcut to disguise the use of hindsight.  

The Federal Circuit has just provided some much needed guidance in its Arendi decision, overturning an obviousness decision by the Patent Office in a post grant proceeding filed by Apple and Google. The Federal Circuit explained that "common sense" has certain limits in terms of supplying missing features as opposed to providing a reason to combine elements from various references. The decision specifically set forth three caveats:

1. Common sense is typically invoked to provide a known motivation to combine, not to supply a missing claim limitation.
2. Using common sense to supply a missing element applies only to rare cases where the missing limitation is unusually simple and the technology particularly straightforward.
3. References to common sense cannot be used as a wholesale substitute for reasoned analysis and evidentiary support.

The Federal Circuit goes on to then analyze the particular invention at issue where the missing limitation relates to enabling a search from within an e-document using an external source outside the document in a particular way not shown in the primary reference. Unfortunately, the analysis seems to also turn on whether certain missing features are the "heart" of the invention:

In cases in which “common sense” is used to supply a missing limitation, as distinct from a motivation to combine, moreover, our search for a reasoned basis for resort to common sense must be searching. And, this is particularly true where the missing limitation goes to the heart of an invention.

What constitutes the "heart" of the invention begs the question of how one determines the "heart" of the invention, or how one determines whether a limitation is "important" or "key." While the decision repeatedly refers to these concepts, it does so without explanation.

In any event, this decision should provide some ammunition to patent applicants in knocking down obviousness rejections based on common sense.