United States Court of Appeals for the Federal Circuit 

04-1414 

BIAGRO WESTERN SALES, INC. and 

THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, 

Plaintiffs-Appellants, 

v. 

GROW MORE, INC., 

Defendant-Appellee. 

Mark D. Miller, Kimble, MacMichael & Upton, of Fresno, California, argued for 

plaintiffs-appellants. With him on the brief were Robert W. Branch and Mary Ann 

Bluhm. 

Alan L. Unikel, Seyfarth Shaw LLP, of Chicago, Illinois, argued for defendantappellee. With him on the brief was Joseph R. Lanser. 

Appealed from: United States District Court for the Eastern District of California 

Senior Judge Robert E. Coyle 
United States Court of Appeals for the Federal Circuit 

04-1414 

BIAGRO WESTERN SALES, INC. and 

THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, 

 Plaintiffs-Appellants, 

v. 

GROW MORE, INC., 

 Defendant-Appellee. 

__________________________ 

DECIDED: September 13, 2005 

__________________________ 

Before GAJARSA, Circuit Judge, PLAGER, Senior Circuit Judge, and DYK, Circuit 

Judge. 

PLAGER, Senior Circuit Judge. 

In this patent infringement case, Biagro Western Sales, Inc. (“Biagro”) and The 

Regents of the University of California (“The Regents”) sued Grow More, Inc. (“Grow 

More”) in the United States District Court for the Eastern District of California. At issue 

is U.S. Patent No. 5,830,255 (“the ’255 patent”), which is entitled “Formulation of 

Phosphorus Fertilizer for Plants.” The Regents are the assignee and Biagro is the 

exclusive licensee of the ’255 patent. 

On cross-motions for summary judgment, the trial court held that Grow More did 

not literally infringe the claims of the patent. The trial court further held that there was 

no infringement under the doctrine of equivalents. Judgment was awarded to Grow 

More. We affirm the judgment of the trial court. 
BACKGROUND 

The United States Patent and Trademark Office (“PTO”) issued the ’255 patent 

on November 3, 1998. At the request of The Regents, to whom the patent had been 

assigned, the PTO undertook a reexamination and issued a reexamination certificate on 

July 11, 2000. As a result of the reexamination, all of the independent claims were 

amended by adding a limitation, originally in several dependent claims, relating to the 

amount of phosphorous-containing acid or salt thereof in the fertilizer formulation. 

After reexamination, claim 1, representative of the independent claims of the ’255 

patent, read: 

A concentrated phosphorus fertilizer comprising a buffered composition 

comprising at least one phosphorous-containing acid or salt thereof such 

that when said composition is diluted with water having a pH of about 6.5 

at a ratio of about 1 part fertilizer to about 40 parts water, there is formed a 

substantially fully solubilized use-dilution fertilizer having a foliageacceptable pH for phosphorus uptake and wherein said phosphorouscontaining acid or salt thereof is present in an amount of about 30 to about 

40 weight percent. 

The emphasized language was added during reexamination to distinguish the claimed 

invention over prior art. That added limitation is the focus of the dispute in this case. 

The term “phosphorous” is an adjectival modifier describing certain compounds 

containing the element phosphorus (P). In the patent, the term “phosphorouscontaining acid” is used to refer to a group of acids that includes phosphorous acid 

(H3PO3), among other acids. ’255 patent, col. 3, ll. 56-60. The patent also states that 

the formulations in the patent are expressed in terms of weight-to-volume, instead of 

weight-to-weight, and therefore the term “weight percent” as used in the claims refers to 

a weight-to-volume percentage. Id. at col. 6, l. 67.

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Grow More’s accused product is a phosphorus fertilizer named Phos-Pro. PhosPro is made by mixing phosphorous acid (H3PO3) with potassium hydroxide (KOH) and 

water. The reaction results in a solution containing two phosphorous acid salts—

dipotassium monohydrogen phosphite (K2HPO3) and potassium dihydrogen phosphite 

(KH2PO3), referred to in abbreviated form as dipotassium phosphite and potassium 

phosphite. A third phosphite, tripotassium phosphite (K3PO3), is present in trace 

amounts. However, and importantly, the final Phos-Pro product does not contain any 

phosphorous acid as such. 

Biagro, as the exclusive licensee of the ’255 patent, filed this patent infringement 

suit against Grow More in July 2000, shortly after the PTO completed reexamination of 

the patent. Grow More filed counterclaims for declaratory judgments of noninfringement and invalidity and for unfair competition under California state law. The 

Regents were eventually joined as a plaintiff.1

The parties filed cross-motions for summary judgment on the question of 

infringement. At issue was the meaning of the added limitation specifying that in the 

claimed fertilizer composition there was a “phosphorous-containing acid or salt 

thereof . . . present in an amount of about 30 to about 40 weight percent.” Biagro 

argued that the limitation can be met in an accused product by calculating a ‘chemical 

equivalent’ amount of phosphorous-containing acid, based on the chemical composition 

of the fertilizer. In the case of the accused Grow More fertilizer, that would be the same 

as the amount of phosphorous-containing acid used in the initial manufacture of the 

product. Grow More argued to the contrary that the limitation referred to the amount of 

 1 Plaintiffs Biagro and The Regents will be referred to collectively as 

“Biagro” throughout the remainder of this opinion. 

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phosphorous-containing acid or salt actually present in the final fertilizer product. The 

trial court construed the limitation as Grow More proposed and, since the Grow More 

final product contained no phosphorous-containing acid, held for Grow More on that 

issue. 

The trial court concluded further that, with regard to the content of acid salts in 

the fertilizer, a fertilizer containing two or more phosphorous-containing salts comes 

within the literal scope of the claim only if the aggregate amount of such salts is 

between about 30 and about 40 weight percent. Based on tests and calculations made 

by Biagro’s expert, the concentration of potassium phosphite in Phos-Pro is 40.3%, and 

the concentration of dipotassium phosphite is 19.0%. Grow More’s calculations 

indicated the phosphite content to be slightly higher based on a different specific gravity 

used to convert weight-to-weight percentages to weight-to-volume percentages. 

According to Grow More’s calculations, the weight-to-volume percentages are 42.2% for 

potassium phosphite and 19.9% for dipotassium phosphite. Thus the total phosphite 

concentration in the accused product is between 59.3% and 62.1%, depending on 

which party’s calculations are used. 

Since the aggregate concentration of the two phosphites in the accused product 

is at least 59.3% weight percent, well outside the claimed range and thus not literally 

infringing, the question was whether the amount of salts could be considered infringing 

under the doctrine of equivalents, that is, whether 60(+/-)% could be considered the 

equivalent of about 30 to about 40%. The trial court chose not to address that question, 

but instead held for Grow More on the ground that, in light of the amended claims, 

prosecution history estoppel acted as a complete bar to a claim of infringement under 

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the doctrine of equivalents according to this court’s en banc decision in Festo Corp. v. 

Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558 (Fed. Cir. 2000) (en banc) 

(“Festo I”), the law in effect at the time. The trial court granted judgment for Grow More. 

Biagro W. Sales, Inc. v. Grow More, Inc., No. CV-F-00-6105 (E.D. Cal. Oct. 18, 2001). 

Biagro filed two motions for reconsideration directed to the issue of whether a 

proper claim construction should permit use of the chemical equivalent analysis. The 

trial court denied both of these motions for reconsideration. Biagro W. Sales, Inc. v. 

Grow More, Inc., No. CV-F-00-6105 (E.D. Cal. Aug. 15, 2002); Biagro W. Sales, Inc. v. 

Grow More, Inc., No. CV-F-00-6105 (E.D. Cal. Apr. 9, 2003). 

Meanwhile, the Supreme Court vacated and remanded our decision in Festo I. 

Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002) (“Festo II”). 

Since final judgment had not yet been entered, the trial judge allowed the parties to file 

briefs addressing whether Biagro could rebut the new ‘Festo presumption’ that the 

patentee had surrendered all subject matter between the original claim limitation and 

the amended claim limitation. While the trial court was considering the matter, we 

rendered our second en banc decision in the Festo case, this time on remand from the 

Supreme Court. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 344 F.3d 1359 

(Fed. Cir. 2003) (en banc) (“Festo III”). 

Biagro argued before the trial court that it could overcome the Festo presumption 

in two of the ways set forth by the Supreme Court in Festo II and further explained in 

Festo III. The trial court rejected both arguments. Biagro W. Sales, Inc. v. Grow More, 

Inc., No. CV-F-00-6105 (E.D. Cal. Mar. 30, 2004). The trial court therefore denied 

Biagro’s motion for reconsideration based on rebuttal of the Festo presumption. 

04-1414 5
The parties stipulated to dismissal without prejudice of Grow More’s counterclaim 

for unfair competition. The trial court had previously deemed Grow More’s counterclaim 

for invalidity withdrawn without prejudice. Thus there were no pending, unresolved 

claims, and the trial court entered final judgment for Grow More. 

Biagro filed a timely appeal. We have jurisdiction pursuant to 28 U.S.C. 

§ 1295(a)(1). 

DISCUSSION 

A. Standard of Review 

We review a grant of summary judgment without deference to the trial court. 

Conroy v. Reebok Int’l, Ltd., 14 F.3d 1570, 1575 (Fed. Cir. 1994). Summary judgment 

is appropriate if there is no genuine issue as to any material fact and the moving party is 

entitled to judgment as a matter of law. Fed. R. Civ. P. 56(c). 

An infringement analysis proceeds first to claim construction to determine the 

scope and meaning of the asserted claims, and second to a comparison of the properly 

construed claims with the allegedly infringing product to determine whether the product 

embodies every limitation of the claims. Cybor Corp. v. FAS Techs., Inc., 138 F.3d 

1448, 1454 (Fed. Cir. 1998) (en banc). Claim construction is a matter of law over which 

we exercise independent review. Id. at 1456. Whether an accused device or method 

infringes a claim, either literally or under the doctrine of equivalents, is a question of 

fact. Bai v. L & L Wings, Inc., 160 F.3d 1350, 1353 (Fed. Cir. 1998). 

Prosecution history estoppel is a legal limitation on the doctrine of equivalents. 

Festo III, 344 F.3d at 1368. Issues relating to the application and scope of prosecution 

history estoppel, including whether the presumption of surrender of subject matter has 

04-1414 6
arisen and whether it has been rebutted, are questions of law to be decided by the 

court. Id. Rebuttal of the presumption may be subject to underlying factual issues, 

which may properly be decided by the court. Id. at 1368 n.3. 

B. Claim Construction 

On appeal, Biagro challenges the trial court’s construction of the claim limitation 

“wherein said phosphorous-containing acid or salt thereof is present in an amount of 

about 30 to about 40 weight percent.” As it did before the trial court, Biagro makes two 

separate arguments, each one corresponding to a different theory. We address each 

theory in turn, and we affirm the trial court’s claim construction under both. 

1. 

Biagro first argues that the amount of phosphorous-containing acid in the claim 

limitation refers to a chemical equivalent amount rather than, as the trial court held, the 

amount of phosphorous-containing acid actually present in the final fertilizer product. 

According to Biagro, the ‘chemical equivalent’ is a calculated amount of phosphorouscontaining acid regardless of whether phosphorous-containing acid is actually present in 

the fertilizer, that is, the amount of phosphorous-containing acid that would react to 

make the final fertilizer. If the amount of phosphorous-containing acid that was used to 

create the product is unknown, the chemical equivalent amount can be derived by 

testing the final product and performing a calculation on the results. 

It is elementary that claim construction begins with, and remains focused on, the 

language of the claims. Innova/Pure Water, Inc. v. Safari Water Filtration Sys., Inc., 381 

F.3d 1111, 1116 (Fed. Cir. 2004). As our recent en banc decision in Phillips v. AWH 

Corp. reaffirmed, the words of a claim are generally given their ordinary and customary 

04-1414 7
meaning, which is the meaning the term would have to a person of ordinary skill in the 

art at the time of the invention. 415 F.3d 1303, 1312-13 (Fed. Cir. 2005) (en banc) 

(citing Innova, 381 F.3d at 1116). Such a person is deemed to read the claim term in 

the context of the entire patent, including the other claims and the written description. 

Id. at 1313. Patent claims should also be construed in light of the prosecution history, 

which, like the patent itself, has been designated as part of the “intrinsic evidence.” Id.

at 1317. Extrinsic evidence, such as expert testimony, may be useful in claim 

construction, but it should be considered in the context of the intrinsic evidence. Id. at 

1318-19. 

In this case, the plain language of the claims gives no indication that the amount 

of phosphorous-containing acid in the claimed invention is a chemical equivalent 

amount. The claim language clearly refers to the “amount” of phosphorous-containing 

acid that is “present” in the “concentrated phosphorus fertilizer.”2

 Furthermore, the 

written description contains no discussion at all of ‘chemical equivalents’ or any hint that 

the amount of phosphorous-containing acid recited in the claims is expressed as a 

chemical equivalent amount instead of the amount actually present in the fertilizer. 

As for the prosecution history of the ’255 patent, Biagro relies on only one 

passage—a statement made by the examiner during reexamination that the phosphite 

solution of a prior art reference was an example of a phosphorous acid solution. At 

most this shows that a person skilled in the art might refer to a phosphite solution as a 

 2 As often happens in claims having an absence of useful punctuation, the 

addition of new language creates ambiguities. In this case, it is unclear whether the 

“wherein” phrase modifies “[a] concentrated phosphorous fertilizer,” or “a buffered 

composition,” or “a fully solubilized use-dilution fertilizer.” For purposes of the result, it 

does not matter. 

04-1414 8
phosphorous acid solution when the phosphite solution, like the accused product in this 

case, was formed from phosphorous acid. But we do not conclude from this one 

statement that one skilled in the art would interpret claim language concerning the 

amount of phosphorous acid required to be “present” in the fertilizer to mean the 

amount of phosphorous acid that was used to make the fertilizer, i.e., the chemical 

equivalent amount. The prosecution history, like the patent itself, is devoid of the term 

chemical equivalent or any reference to the use of representative amounts to describe 

the composition of the fertilizers claimed in the patent. 

Biagro also cites the prosecution history of U.S. Patent No. 6,113,665 (“the ’665 

patent”), which is a continuation of the ’255 patent and was prosecuted during the same 

timeframe as the reexamination of the ’255 patent. In remarks accompanying two 

amendments that added limitations on the amount of phosphorous-containing acid or 

salt present in the claimed fertilizer, the applicant’s attorney referred to the amount of 

phosphorous acid “in” examples 1 and 9 of the written description. According to Biagro, 

these amounts were chemical equivalent amounts because the fertilizers produced in 

those examples do not actually contain phosphorous acid. As the trial court noted, 

however, there is nothing in the prosecution history of the ’665 patent to explain how the 

figures were obtained or to indicate that the examiner understood the applicant was 

referring to chemical equivalent amounts. Whatever the attorney’s statements were 

intended to mean, they do not alter the ordinary meaning of the claim language, i.e., 

that the amount of phosphorous-containing acid is the amount actually present in the 

fertilizer. 

04-1414 9
In making its arguments, Biagro relies heavily on extrinsic evidence in the form of 

expert declarations explaining fertilizer labeling guidelines and standards. This 

evidence, according to Biagro, shows that those skilled in the art understand that the 

amounts of plant nutrients in fertilizer products are frequently expressed as ‘chemical 

equivalents.’ The primary example is a fertilizer labeling convention, known as the 

‘guaranteed analysis,’ which indicates the guaranteed amount of nitrogen, phosphorus, 

and potassium in the fertilizer product. The phosphorus content is expressed not in its 

elemental form (P), but as phosphorus pentoxide (P2O5), regardless of whether the 

fertilizer actually contains any phosphorus pentoxide. Thus the amount of phosphorus 

pentoxide listed on the label is a chemical equivalent amount derived from the actual 

chemical composition of the fertilizer. Biagro also cites California fertilizer labeling 

guidelines that refer to fertilizer products as “containing” phosphorous acid when in fact 

they were only derived from phosphorous acid. In Biagro’s view, this evidence shows 

that a person skilled in the art would understand the claims to refer to a chemical 

equivalent amount of phosphorous-containing acid, and therefore we should accept this 

interpretation as the ordinary and customary meaning of the claim language. 

However, even if we agree that the labeling convention and guidelines 

demonstrate that those skilled in the art are familiar with the use of ‘chemical 

equivalents,’ the problem is that Biagro cannot tie its extrinsic evidence to the patent or 

the claim language. Nothing in the patent or prosecution history indicates that labeling 

standards are relevant to the claimed fertilizer, and nothing in Biagro’s extrinsic 

evidence suggests that a person skilled in the art of fertilizer formulation would 

04-1414 10
necessarily use a chemical equivalent to express the amount of phosphorous acid in a 

fertilizer that does not actually contain phosphorous acid. 

We are also unpersuaded by Biagro’s argument that Grow More’s expert took an 

inconsistent position on behalf of a different defendant in another patent infringement 

suit brought by Biagro. In that case, the expert described a prior art fertilizer as 

containing 13% phosphorous acid, which was ultimately shown to be a chemical 

equivalent amount. We agree with the trial court that it appears the expert was simply 

relying on product materials shown to him and was not aware that the 13% had been 

arrived at through a ‘chemical equivalent’ analysis. 

2. 

Biagro’s second theory is that the trial court erred in construing the amount of 

“phosphorous-containing acid or salt” in the claim language as an aggregate amount. 

The claim language calls for “at least one phosphorous-containing acid or salt 

thereof . . . wherein said phosphorous-containing acid or salt thereof is present in an 

amount of about 30 to about 40 weight percent.” Biagro argues that the limitation is met 

so long as one acid or salt is present in the claimed amount, even if the fertilizer 

contains other acids or salts. Under the trial court’s claim construction, as advocated by 

Grow More, a fertilizer containing more than one acid or salt would satisfy the limitation 

only if the aggregate amount of acids or salts falls within the claimed range. 

The phrase “at least one” in patent claims typically is construed to mean “one or 

more.” Therefore, Biagro contends, the claim language allows for aggregation of acids 

or salts but does not require it. The trial court, however, concluded that both the written 

description and prosecution history require the aggregate amount of acids or salts to be 

04-1414 11
within the claimed range, and we agree. First, it is apparent from the written description 

that all phosphorous-containing acids or salts in the fertilizer serve the same purpose 

such that the total amount of such acids or salts is important. More significantly, during 

reexamination the patentee distinguished the invention over prior art by emphasizing 

that the claimed fertilizer “must be concentrated” and that the “concentration has now 

been specified as an amount of about 30 to about 40 weight percent.” If a fertilizer 

contains more than one phosphorous-containing acid or salt, the concentration is based 

on the total amount of such acids or salts, not just one acid or salt. In view of the 

patentee’s emphasis on the concentration of phosphorous-containing acids or salts, the 

trial court correctly construed the claim to require an aggregate amount of such acids or 

salts to be between about 30 and about 40 weight percent. 

C. Infringement 

1. Literal Infringement 

Having affirmed the trial court’s claim construction, we also affirm the trial court’s 

grant of summary judgment of no literal infringement with respect to both of the theories 

presented by Biagro. First, because we have rejected Biagro’s chemical equivalent 

claim construction argument, there can be no literal infringement based on the amount 

of phosphorous acid, an ingredient used to make the accused fertilizer but not actually 

present in the final product. 

Biagro’s second literal infringement theory is that potassium phosphite is present 

in the accused product in an amount of 40.3%, which Biagro alleges is within the 

claimed range of “about 30 to about 40 weight percent.” The correct claim construction, 

however, requires the aggregate amount of phosphites to be within the claimed range. 

04-1414 12
Because the accused product contains two phosphites, resulting in an aggregate 

phosphite content of at least 59.3%, clearly outside the claimed range, no reasonable 

jury could find literal infringement based on the presence of phosphites. 

2. Infringement Under the Doctrine of Equivalents 

Biagro also asserts that Grow More’s fertilizer infringes the claims of the ’255 

patent under the doctrine of equivalents because the aggregate phosphite concentration 

of between 59% and 62% is equivalent to the claimed concentration of about 30 to 

about 40 weight percent. The trial court did not reach the issue in those terms in its 

initial summary judgment order because it held that, under Festo I, prosecution history 

estoppel acted as a complete bar to a claim of infringement by equivalents. Later, after 

the Supreme Court’s Festo II decision and this court’s Festo III decision on remand, the 

trial court reconsidered its summary judgment ruling, but still held that Biagro was 

barred from asserting the doctrine of equivalents because it failed to rebut the Festo

presumption. 

A narrowing amendment made for a substantial reason relating to patentability 

gives rise to a presumption that the patentee has surrendered all subject matter 

between the original claim limitation and the amended claim limitation. Festo III, 344 

F.3d at 1367. If the narrowing amendment was the addition of a new claim limitation, as 

in the case before us, equivalents are presumptively not available with respect to that 

limitation. Honeywell Int’l Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131, 1141 (Fed. 

Cir. 2004). 

A patentee may rebut the presumption of surrender by showing that at the time of 

the amendment one skilled in the art could not reasonably be expected to have drafted 

04-1414 13
a claim that would have literally encompassed the alleged equivalent. Festo II, 535 U.S. 

at 741. The Supreme Court identified three ways in which the patentee may overcome 

the presumption. The patentee may show that the alleged equivalent would have been 

unforeseeable at the time of the amendment, that the rationale underlying the 

amendment bore no more than a tangential relation to the equivalent in question, or that 

there was “some other reason” that the patentee could not reasonably have been 

expected to have described the alleged equivalent. Id. at 740-41. 

As an initial matter, we reject Biagro’s argument that at the summary judgment 

stage the burden is on Grow More to present undisputed facts showing that Biagro 

cannot rebut the Festo presumption. The Supreme Court made clear that the patentee 

bears the burden of rebutting the presumption of surrender. Id. at 740. Furthermore, 

the determination of whether the presumption has been rebutted is a question of law. 

Festo III, 344 F.3d at 1368. Although in some situations there may be underlying 

factual issues, id. at 1368 n.3, neither of Biagro’s rebuttal arguments involves disputed 

facts, as will be explained below. 

We begin by examining the amendment that was made to the claims of the ’255 

patent. During reexamination, the patentee made a narrowing amendment to all of the 

independent claims by adding the claim limitation “wherein said phosphorous-containing 

acid or salt thereof is present in an amount of about 30 to about 40 weight percent.” 

The amendment was made to overcome a prior art obviousness rejection based on a 

reference describing a fertilizer that was buffered only when diluted. To distinguish the 

claims over the prior art reference, the patentee explained to the examiner that the 

fertilizer must be concentrated and that the amendment specified a range for the 

04-1414 14
concentration. Therefore the narrowing amendment was made for a reason 

substantially related to patentability, and Biagro has presumptively surrendered any 

equivalents with respect to the amount of phosphorous-containing acid or salt present in 

the fertilizer. 

Biagro first attempts to rebut the presumption of surrender by arguing that the 

rationale underlying the amendment was no more than tangentially related to the 

asserted equivalent. As we explained in Festo III, whether the patentee has overcome 

the presumption on this ground is determined by the court on the basis of the public 

record. Id. at 1369-70. In this case, it is clear from the prosecution history that the 

reason for adding the range limitation was to overcome a prior art fertilizer that was not 

concentrated. 

Here the alleged equivalent is a fertilizer with a phosphite concentration of nearly 

60%. Because both the reason for the amendment and the asserted equivalent relate 

to the concentration of the fertilizer, we affirm the trial court’s conclusion that Biagro has 

not shown that the rationale underlying the amendment was merely tangential to the 

accused equivalent. 

We disagree with Biagro that this case is analogous to Insituform Technologies, 

Inc. v. Cat Contracting, Inc., 385 F.3d 1360 (Fed. Cir. 2004). That case involved a 

method for impregnating a tube liner with a resin by moving a single vacuum cup to 

multiple points along the tube liner. The accused process used multiple vacuum cups, 

and the patentee asserted that the multiple-cup process was equivalent to the singlecup process. The original claim did not specify the number or location of vacuum cups. 

During prosecution, the patentee incorporated several limitations from dependent claims 

04-1414 15
into independent claim 1. The prosecution history showed that the reason for the 

amendment was to overcome a prior art process that used a single vacuum source at 

the end of the tube liner distant from the resin source. Thus the reason for the 

amendment and the alleged equivalent involved different aspects of the invention—the 

location of the vacuum source relative to the resin versus the number of vacuum cups. 

Id. at 1370. Accordingly, we concluded that the rationale underlying the amendment 

was tangential to the allegedly equivalent process. In contrast, the reason for the 

amendment and the accused equivalent in the case before us both relate to the 

concentration of the fertilizer. 

Biagro also argues that because only the lower limit of the claimed range was 

necessary to distinguish over prior art, the reason for the amendment is merely 

tangential to an accused equivalent at the upper end of the range. In effect, Biagro is 

arguing that there was no reason for adding an upper limit of 40%. Viewed from that 

perspective, the situation is analogous to the amendment in Festo that added the 

“magnetizable” limitation. The prosecution history revealed no reason for the 

amendment, and therefore Festo could not show that the rationale underlying the 

amendment was only tangential to the accused nonmagnetizable equivalent. Festo III, 

344 F.3d at 1371-72. Similarly, in this case, since the prosecution history shows no 

reason for adding an upper limit to the concentration range, Biagro cannot claim that the 

rationale for the amendment is merely tangential. 

Biagro further argues that it can rebut the Festo presumption of surrender with 

“some other reason” that the patentee could not reasonably have been expected to 

have described the alleged equivalent when it narrowed the claim. That “other” reason 

04-1414 16
is that the patentee allegedly understood the claim language to refer to a chemical 

equivalent amount of phosphorous acid. We agree with the trial court that Biagro’s 

contention should be rejected as merely an attempt to reargue the claim construction 

issue. Moreover, we fail to see how the patentee’s supposed inability to draft claims to 

cover chemical equivalent amounts relates to Biagro’s equivalence argument, which is 

that the approximately 60% concentration of phosphite actually present in the accused 

product is equivalent to the claimed 30-40% concentration. 

For the reasons discussed, we affirm the trial court’s holding that Biagro has not 

rebutted the presumption of surrender and that prosecution history estoppel bars Biagro 

from asserting infringement under the doctrine of equivalents. 

CONCLUSION 

The judgment of the trial court is in all respects 

AFFIRMED. 

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