“Common sense” vs. “Common knowledge”

The issue of “common sense” came up again in the oral arguments before the Federal Circuit.  In Siemens AG v. Seagate Technology, 2009-1382 (Fed. Cir. March 9, 2010), the panel questioned appellant’s counsel about “common sense” in regard to a highly technical field of art.  The question was whether “common sense” in a KSR analysis of a highly technical area refers to the “common sense” of an ordinary individual or the “common sense” of one of ordinary skill in the highly technical field of art at issue. [Listen]

In the opinion written by Judge Archer, the panel avoided the “common sense” issue and referred  instead to “common knowledge”:   

The jury implicitly found that all asserted claims of the ‘838 patent were rendered obvious by known giant magnetoresistive (“GMR”) sensors combined with a coupling layer and magnetic layer from known artificial antiferromagnets (“AAF”). Siemens asserts that there was no motivation to make this combination. However, Seagate’s expert, Dr. Wang, testified that AAF structures with a coupling layer and a magnetic layer were known to those of ordinary skill in the art in 1992 and were also found in prior art patents and publications. Dr. Wang further explained in detail that based on this common knowledge of AAFs and known problems with prior art GMR sensors (such as stray magnetic flux) and the design incentives for solving such problems, a person of ordinary skill in the art would have been motivated to solve these problems using an AAF. In light of Dr. Wang’s testimony, a reasonable jury could have found that it would have been obvious to one of ordinary skill in the art to combine known GMR sensors with the coupling and magnetic layers from known AAFs to make the claimed invention.


 Black’s Law Dictionary defines both “common knowledge” and “common sense”:

Common Knowledge.  Refers to what court may declare applicable to action without necessity of proof.  It is knowledge that every intelligent person has, and includes matter of learning, experience, history and facts of which judicial notice may be taken.  Shelley v. Chilton’s Adm’r, 236 Ky. 221, 32 S.W.2d 974, 977.  See also Judicial notice.


Common Sense.  Sound practical judgment; that degree of intelligence and reason, as exercised upon the relations of persons and things and the ordinary affairs of life, which is possessed by the generality of mankind, and which would suffice to direct the conduct and actions of the individual in a manner to agree with the behavior of ordinary persons.


You can listen to the entire oral argument here: [Listen].

You can read the court’s opinion here: [Read].

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