The Federal Circuit’s August 27, 2013 decision in Applied Medical Resources Corp. v. Tyco Healthcare Group LP (Case No. 2012-1412) (nonprecedential) relied on the seldom-used “difference in kind” test in analyzing infringement under the doctrine of equivalents, considering whether an accused product was different in kind – rather than just degree – from the claimed invention. The concept of “difference in kind” is not new, but is cited infrequently, and usually only in passing. It was introduced as a refinement to the better known claim vitiation test, which allows courts to find non-infringement as a matter of law if a theory of equivalence would “vitiate” a claim element. Applied Medical shows that the difference-in-kind test can be an important supplement to claim vitiation analysis, particularly in cases where clear-cut distinctions can be drawn between the claimed invention and the accused device.

In Applied Medical, Applied had appealed from the district court’s grant of summary judgment that Tyco’s surgical trocar tools did not infringe Applied’s patent literally or under the doctrine of equivalents. A trocar is a device which provides an access port through which thin instruments may be inserted into a patient’s body during laparoscopic surgery. Applied’s patent claimed a trocar with an “instrument seal assembly” capable of sliding side to side within the trocar like a hockey puck, allowing the surgeon to move instruments laterally in the trocar. The patent claims specifically required “free lateral movement” of the entire instrument seal assembly, as opposed to just the opening through which instruments are passed. Tyco’s accused devices, by contrast, used a gimbaled instrument seal assembly which, instead of sliding side to side, pivoted about a fixed point, allowing the surgeon to angle the instruments as desired. Thus, although Tyco’s instrument opening moved from side to side, the assembly itself did not.

The Federal Circuit agreed that the doctrine of claim vitiation precluded a finding of infringement under the doctrine of equivalents. The Court did not stop there, however. Noting that the district court’s analysis had been only “brief,” Judges Prost, Schall and Reyna applied the difference-in-kind test, explaining that “[o]ur case law indicates that a finding of infringement under the doctrine of equivalents vitiates a claim limitation when the aspect of the accused device that allegedly meets that limitation represents a difference in kind from what is claimed in the limitation.” The Court found that there could be no infringement under the doctrine of equivalents because “the ‘kind’ of instrument seal assembly claimed is one that moves [] from side to side” while Tyco’s device “is [] not that ‘kind’ [because] it does not move side to side at all.”

The sort of black and white distinction drawn in Applied Medical appears to be typical of cases invoking the difference in kind test. For example, in Freedman Seating Co. v. Am. Seating Co., 420 F.3d 1350, 1361 (Fed. Cir. 2005), the Federal Circuit applied the test to an almost identical set of facts as Applied Medical, finding that a fixed, rotating part was different in kind than a sliding part. Similarly, in Sanofi-Aventis Deutschland GMBH v. Genentech, Inc., 2011 U.S. Dist. LEXIS 28334, *39 (N.D. Cal. Mar. 7, 2011), a district court observed (unsurprisingly) that “[a] linear, chromosomal molecule is different in kind from a circular, extrachromosomal molecule.”

This is not to say that the difference-in-kind test is an exercise in stating the obvious. In Van Blarcom Closures, Inc. v. Owens-Illinois, Inc., 507 F. Supp. 2d 214 (E.D.N.Y. 2006) the difference-in-kind test was determinative in resolving a close case in which the patent claims were directed narrowly to a child-proof bottle cap with projections on the inner rim of the cap, while the accused product had projections along the underside of the top of the cap. The district court was compelled to find that the caps were different in kind (rather than degree) such that there could be no infringement under the doctrine of equivalents. In doing so, the court observed that:

[the] plaintiff may be wondering when the doctrine [of equivalents] would ever apply, if not in a case with as seemingly minor a difference between the accused device and the patent claim as this one. The answer is that, where the claimed invention is a simple structural device in an already crowded art, and the claim limitations are clearly stated and sharply defined, and the variation presented by the accused device was foreseeable to the patent drafter, there may indeed be few, if any, infringing equivalents.

Thus, the difference-in-kind test may provide the dispositive analysis in close cases, particularly in mechanical fields.