CAFC analyzes prosecution history estoppel in Pharma Tech v. LifeScan. Defendant LifeScan wins.

The outcome of Pharma Tech:


This is an appeal from the district court’s summary
judgment of noninfringement under the doctrine of equivalents.
Because prosecution history estoppel bars the
claims for infringement under the doctrine of equivalents,
we affirm.



The technical matter involves electrochemistry:


To test blood glucose, an
individual typically draws blood by pricking a finger, placing the blood
on the end of a test strip, and placing the test
strip into a meter. The test strip contains a pair of electrodes, including
a working electrode and a second electrode. The working electrode is coated with an enzyme that
oxidizes glucose in the blood sample. Following an incubation period, the meter
(1) applies a known electric potential
across the electrodes, creating a diffusion limiting electric
current (referred to as the “Cottrell current”) through the
sample; and (2) measures Cottrell current. A proportional
relationship exists between the measured current and
blood glucose concentration. Based on this proportional relationship,
a microprocessor in the meter converts the
measured electric current to a blood glucose level and then
reports the blood glucose level to the user.




Following failed dismissal motions under FRCP 12, LifeScan went
for summary judgment, on which LifeScan prevailed at district court:


LifeScan asserted that argument-based and amendmentbased prosecution
history estoppel barred Pharma Tech’s
doctrine of equivalents infringement theory.
(...)
The court
reasoned that LifeScan’s accused system falls within the
claim scope surrendered by the inventors during prosecution of the ’069 patent. In so ruling,
the district court concluded that the tangentiality exception did not apply
because the inventors’ remarks during prosecution indicated that “comparison of analyte
concentration measurements was, at a minimum, a significant aspect of the
[October 1997] amendment.” Pharma Tech Sols. Inc. v.
LifeScan Inc., 348 F. Supp. 3d 1076, 1084 (D. Nev. 2018).
The district court further held that argument-based estoppel likewise barred Pharma Tech’s
claims, noting that the
inventors “consistently relied on the comparison of two analyte concentration measurements
as a distinguishing feature of [their] claims.” Id. Accordingly, the district court
granted LifeScan’s motion for summary judgment.



The CAFC cited Festo:



“Prosecution history estoppel applies as part of an infringement analysis to prevent a patentee from using the
doctrine of equivalents to recapture subject matter surrendered from the literal scope of a claim during prosecution.”
Trading Techs. Int’l, Inc. v. Open E Cry, LLC, 728 F.3d
1309, 1322 (Fed. Cir. 2013). Prosecution history estoppel
can occur in two ways: “either (1) by making a narrowing
amendment to the claim (‘amendment-based estoppel’) or
(2) by surrendering claim scope through argument to the
patent examiner (‘argument-based estoppel’).” Conoco,
Inc. v. Energy & Envtl. Int’l, L.C., 460 F.3d 1349, 1363
(Fed. Cir. 2006).
With respect to amendment-based prosecution history
estoppel, the Supreme Court has recognized that a “patentee’s decision to narrow his claims through amendment
may be presumed to be a general disclaimer of the territory
between the original claim and the amended claim.” Festo
Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S.
722, 740 (2002). The presumption may be overcome if the
patentee can show the applicability of one of several exceptions identified by the Supreme Court: (1) the equivalent
was “unforeseeable at the time of the application”; (2) “the
rationale underlying the amendment may bear no more
than a tangential relation to the equivalent in question”; or
(3) “there may be some other reason suggesting that the
patentee could not reasonably be expected to have described the insubstantial substitute in question.” Id.
at 740–41.

(...)

“The tangential relation inquiry ‘focuses on
the patentee’s objectively apparent reason for the narrowing amendment,’ which ‘should be discernible from the
prosecution history record.’” Integrated Tech. Corp. v. Rudolph Techs., Inc., 734 F.3d 1352, 1358 (Fed. Cir. 2013)
(quoting Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki
Co., 344 F.3d 1359, 1369 (Fed. Cir. 2003)).



Insituform is also cited:



Finally, Pharma Tech analogizes the facts here to those
in cases where we held that amendment-based prosecution
history estoppel did not apply. For example, Pharma Tech
argues that Insituform Technologies, Inc. v. CAT Contracting, Inc., 385 F.3d 1360 (Fed. Cir. 2004), controls the result
here. We disagree. In Insituform, the remarks accompanying the patentee’s amendment did not emphasize or rely
on the added claim language to distinguish the prior art in
a manner relevant to the asserted equivalent. Id. at 1370.
This court held that Insituform’s amendment narrowing
the claim to a one-cup vacuum process located near a resin
source was merely tangentially related to an equivalent
multiple-cup vacuum process because the rationale underlying the amendment “was to avoid the need to use a large
compressor when the vacuum is created a significant
distance from the resin source.” Id. (quoting Insituform
Techs., Inc. v. Cat Contracting, Inc., 161 F.3d 688, 692
(Fed. Cir. 1998)). Insituform noted “no indication in the
prosecution history of any relationship between the narrowing amendment and a multiple cup process.” Id.
Here, by contrast, the applicants’ October 1997 amendment sought to avoid prior art systems that measured and
displayed diffusion limiting current. To distinguish their
claims from Kuhn, Pollmann, and Szuminsky, which measured and displayed diffusion limiting current, the inventors amended their claims to require obtaining a plurality
of current readings, converting the current readings to analyte concentration measurements, and comparing the analyte concentration measurements to detect errors. The
inventors’ remarks accompanying the October 1997
amendment distinguished the prior art based on the newly
added sequential “converting” and “comparing” limitations. It is undisputed that—like the prior art—LifeScan’s
meter does not convert diffusion limiting current readings
to analyte concentration measurements and then compare
analyte concentration measurements to one another to detect errors.