Primos v. Hunter: No Festo Estoppel When Newly Added Term is Found in the Accused Product

PrimosPrimos v. Hunter’s Specialties (Fed. Cir. 2006, 05–1001).

Primos owns patents on game calls for hunting. In an infringement suit, a jury found that Hunter’s products literally infringed one patent and infringed another under the doctrine of equivalents (DOE).

On appeal, Hunter challenged the DOE decision arguing both (1) Festo Estoppel and (2) Vitiation.  In a surprise boost to the DOE, the CAFC affirmed — finding that the DOE could be asserted.

Estoppel:  Hunger argued that a claim amendment made during prosecution created an estoppel that, under Festo, prevented assertion of the DOE.  Primos countered that Festo estoppel should not apply because the “amendment bears no more than a tangential relationship to the accused element.”

As the Supreme Court explained in Festo, when a patent claim is amended during prosecution for reasons relating to patentability, there is a presumption that the patentee surrendered all the territory between the original claim limitation and the amended claim limitation. 535 U.S. at 740. There are situations, however, in which a patentee may overcome that presumption. Id. One such situation is when the “rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question.” Id. at 740-41.

Here, Primos had twice amended the claim to: (1) require that the “plate” have “a length” and (2) require that the plate be “differentially spaced” above the membrane.  Because “every physical object has a length,” the first amendment did not narrow the scope of the claim.  The accused product included a differentially spaced dome rather than a differentially spaced plate as claimed.  “Because the accused device’s dome includes the spacing, the amendment was merely tangential to the contested element in the accused device, and thus prosecution history estoppel does not apply to prevent the application of the doctrine of equivalents.”

Thus, this holding implies that Festo estoppel does not apply when the newly added limitation (or term) is found in the accused product. 

Vitiation: The Court had streak expanding the vitiation doctrine under the all-elements rule.  Here, Hunter asserted that allowing a “dome” to be considered an equivalent to a “plate” would eliminate (or vitiate) that limitation from the claim.  The CAFC balked at Hunter’s implicit suggestion that there might be no equivalent for the claimed plate:

Our precedent has recognized that “[t]here is no set formula for determining whether a finding of equivalence would vitiate a claim limitation, and thereby violate the all limitations rule. Rather, courts must consider the totality of the circumstances of each case and determine whether the alleged equivalent can be fairly characterized as an insubstantial change from the claimed subject matter without rendering the pertinent limitation meaningless.” Thus, because Primos’s theory of equivalence (i.e., that a dome is equivalent to the claimed “plate”) does not “effectively eliminate . . . [the ‘plate’ limitation] in its entirety,” it does not violate the all limitations rule.

This case is in line with my alternate theory that vitiation only applies to linkages and noun modifiers.

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7 thoughts on “Primos v. Hunter: No Festo Estoppel When Newly Added Term is Found in the Accused Product

  1. Helpful Friend —

    You are over-simplifying the issue because there was not literal infringement.

    Original Claim: plate.
    Amended Claim: differentially spaced plate.
    Accused Product: differentially spaced dome.

    The question was whether Festo-type estoppel prevents application of the doctrine of equivalents in this case.

  2. Why not just say that the doctrine of equivalents is unnecessary when there is literal infringement? Reread your statement:

    “[T]his holding implies that Festo estoppel does not apply when the newly added limitation (or term) is found in the accused product.”

  3. We’ll have to see how future CAFC panels interpret the phrase “contested element.” I actually hope that Dennis is correct because it will preserve the doctrine of equivalents in more instances.

  4. Good comment SF. However, based on the very clear language of the opinion, I am sticking by my “implication.”

    From the opinion: “Because the accused device’s dome includes the spacing, the amendment was merely tangential to the contested element in the accused device. . . ”

    One difficult concept here (and one that the CAFC has never addressed) is the meaning of a claim element or claim limitation. If we are doing an element by element analysis (as required), is a “plate” an element, or is the element theh “differentially spaced element.”

    One very smart attorney that I know uses lots of hyphens to tie words together help readers differentiate between various elements.

  5. The case states, “Because the accused device’s dome includes the spacing, the amendment was merely tangential to the contested element in the accused device, and thus prosecution history estoppel does not apply to prevent the application of the doctrine of equivalents.”

    Dennis argues that this holding implies that “Festo estoppel does not apply when the newly added limitation (or term) is found in the accused product.”

    I disagree. I think the tangentiality was determined by the defendant’s argument–not the fact that the newly added limitation was found in the accused product.

    Here, an element (a plate) originally present in the claim was amended to include an additional limitation (spacing). The court stated, “Hunter’s Specialties challenges the application of the doctrine of equivalents on the ground that prosecution history estoppel applies to the term ‘plate.'” In particular, the defendant argued that estoppel applied to “plate” and that its dome was not the equivalent of a plate. Well, what does spacing have to do with whether the dome is equivalent of a plate? Apparently nothing. Thus, the spacing was tangential (actually irrelevant) to whether the dome was an equivalent of a plate.

    What if the newly added limitation (spacing) affected the function of the existing element (the plate) and the allegedly equivalent structure (the dome) in materially different ways? Couldn’t the defendant argue that a “spaced dome” was not equivalent to a “spaced plate”–and thus the spacing would not be tangential? I think so. But the defendant didn’t make that argument here–probably because spacing did not make a material difference under the facts of the case. However, with different facts, a newly added limitation may make a material difference.

    The underlying issue of this case was whether tangentiality should be viewed relative to [1] only to the newly added limitation (spacing) or [2] both the newly added limitation (spacing) and the element it modified (plate). In the future, I believe this tangentiality issue will turn on how the newly added limitation affects [1] the element it modifies and [2] the allegedly equivalent structure–not whether the newly added feature is found in the accused device.

  6. What’s wrong with that statement, Helpful Friend? It seems to me to be a reasonable interpretation of the case. When the newly added term (in this case “differential distance”) applies to the pointed-to equivalent structure in the accused device, then the amendment is merely tangential to the equivalent in question. You could fight about whether that’s good law, but it does seem a reasonable interpretation of the opinion.

  7. “[T]his holding implies that Festo estoppel does not apply when the newly added limitation (or term) is found in the accused product.” Ummm…you can’t be serious. Think before you write.

    -Helpful Friend

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