CAFC defines “common sense” and warns against impermissible hindsight

Ryan Chirnomas | June 6, 2012

Mintz and Jif-Pak Manufacturing v. Dietz & Watson and Package Concepts and Materials

May 30, 2012

Rader, Newman, Dyk.  Opinion by Rader.


This case highlights the important point that obviousness cannot be established by vague and unsubstantiated reliance on “common sense.”  Rather, Judge Rader defines the term “common sense” as “knowledge so basic that it certainly lies within the skill set of an ordinary artisan.”  The CAFC also warns against hindsight due to defining the problem to be solved based on the solution found by the inventors.   Furthermore, the CAFC reminds us that when references from a secondary technical field are used in a rejection, the person of ordinary skill in the art is not a person familiar merely with this secondary technical field, but rather a person familiar with at least the primary technical field.


Mintz is the inventor of U.S. Patent 5,413,148, which covers casings for meat products such as deli meats.  Commercial embodiments of the invention can be seen in products manufactured by Mintz’s company, Jif-Pak.  Package Concepts and Materials (“PCM”) was a former distributor of Jif-Pak’s product who introduced a similar product after their relationship with Jif-Pak ended.  Mintz sued for infringement.  The district court granted PCM’s motion for summary judgment, ruling that the patent was invalid and that PCM’s product did not infringe the ‘148 patent.  Mintz appealed to the CAFC.

A representative claim from the ‘148 patent is as follows (the disputed claim term is underlined):

1. An elongated tubular casing structure for encasing meat products, said elongated structure having a longitudinal direction and a transverse lateral direction, said casing structure comprising:

a stockinette member comprising a closely knit tubular member formed of closely knit threads and having a first stretch capacity;

a knitted netting arrangement having a second stretch capacity and comprising a first plurality of spaced strands extending in said longitudinal direction extending in said lateral direction;

the longitudinal and lateral strands of said netting arrangement each intersecting in locking engagement with one another to form a grid-like pattern comprising a plurality of four-sided shapes;

said strands of said netting arrangement being knit into the threads of said stockinette member, whereby said netting arrangement and said stockinette member are integrally formed so that said casing structure comprises an integrally formed structure;

said first stretch capacity being greater than said second stretch capacity;

whereby, when a meat product is stuffed into said casing structure under pressure, said meat product forms a bulge within each of said four-sided shapes to thereby define a checker-board pattern on the surface thereof, said stockinette member forming a shield to prevent the adherence of adjacent meat product bulges over said strands of said netting arrangement.

As to the disputed claim term, “locking engagement,” in a Markman hearing, the district court found this term to mean “fixed at each intersection.”  The term “locking engagement” was added during prosecution to overcome an obviousness rejection.

Prior art casing structures used netting structures which achieved the desirable “checkerboard” pattern on the exterior of the meat, but had a problem in that the meat would bulge and cook around the strands of the netting, thus adhering to itself and making the strands difficult to remove.  Other prior art casing structures included another layer (a “stockinette”) underneath the netting to avoid this problem, but these casing structures required a labor-intensive two-step stuffing process.  The ‘148 patent solved both problems by integrating the stockinette and the knitting with different stretching abilities.


Person skilled in the art

PCM challenged the validity of the patent based on three references, all three of which were previously applied by the Examiner during prosecution.  Of the three references, only one related to meat encasements—the other two related to knitting of fabrics such as socks.  However, the district court stated that one having ordinary skill in the art would have familiarity with the knitting art but not with the meat encasing art.

This marks the first of three clear errors made by the district court in their analysis of the Graham factors.  Citing numerous references to meat encasement throughout the ‘148 patent, the CAFC stated that understanding of the meat encasement art was required for a person of ordinary skill in the art to grasp various aspects of the invention.  As such, the district court erred in their identification of the person having ordinary skill in the art.

However, the CAFC also pointed out that the inclusion of the meat encasing arts would not prevent knitting references from being considered as analogous.  In other words, references from a secondary technical field can be analogous in some situations, but it is not permissible to exclude the primary technical field in the identification of the ‘person having ordinary skill in the art.’

Difference between the prior art and the claimed invention

The district court correctly identified the lack of a “locking engagement” as being the difference between the combination of prior art and the claimed invention.  The district court relied on “a common sense view” or “common sense approach” in arriving at the position that it would have been obvious to try the “locking engagement.”  The CAFC ruled that this was an overreach, and was indicative of hindsight.  In particular, the CAFC stated:

The mere recitation of the words “common sense” without any support adds nothing to the obviousness equation.  Within the statutory test to determine if a claimed invention has advanced its technical field enough to warrant an exclusive right, “common sense” is a shorthand label for knowledge so basic that it certainly lies within the skill set of an ordinary artisan.

The CAFC then referred back to its previous point framing the person skilled in the art as a person having at least some experience in the meat encasement arts, stating that a person skilled in the knitting arts likely has different knowledge from a person skilled in the meat encasement arts.

Next, the CAFC criticized as clear error the district court’s framing of the obviousness question as whether it would have been obvious to fix the points of intersection in order to solve the problem of forming a checkerboard pattern.  In the CAFC’s eyes, this analysis was merely one of hindsight which framed the problem only in context of the eventual solution.

Instead, according to the CAFC, the obviousness question should have been whether a person skilled in the meat encasement arts would have recognized the problem of adherence of two sections of meat on either side of the strands, and solved the problem in the manner that the inventors did.  No evidence on this point was provided.

Objective indicia of nonobviousness

Mintz and Jif-Pak provided considerable evidence of unexpected results, expert skepticism, copying, commercial success, failure by others, long-felt need, and praise by others (including praise by PCM during their period as a Jif-Pak distributor).  However, the district court stated that “Plaintiffs do not appear to offer any objective evidence of nonobviousness.”  The CAFC viewed the district court’s statement as inexplicable, and ruled that the district court erred by ignoring the objective indicia of non-obviousness.

Validity summary

In view of the district court’s clear error with respect to the level of ordinary skill in the art, the differences between the prior art and the invention, and objective evidence of nonobviousness, the CAFC remands the case to the district court for proper fact finding of the Graham factors, if the ‘148 patent is still in contention in view of the non-infringement holding below.


In spite of the above, the CAFC also found non-infringement of the ‘148 patent, since the district court was correct with respect to its non-infringement ruling.  In particular, the CAFC found that the accused products have the same feature as that found in the prior art with respect to the manner of engagement of two strands of the netting material.  Mintz had argued “locking engagement” as a point of distinction during prosecution.  However, since the accused product had the identical engagement scheme as in the cited art, the accused products did not meet the limitation of the “locking engagement.”  As such, the CAFC affirmed the non-infringement holding of the district court.

Practice tips

This case may provide some helpful support when arguing against a rejection in which an Examiner relies on unsubstantiated “common sense” reasoning.  In such a case, it might be helpful to argue that the Examiner’s reasoning for modifying cited art is not “knowledge so basic that it certainly lies within the skill set of an ordinary artisan.”

Furthermore, this case may also prove helpful when responding to a rejection where different technology fields are used together as analogous art.  This case supports the point that the focus of the person having ordinary skill in the art should be kept on the primary technical field, even if references from other technologies are properly included in a rejection.

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