United States Court of Appeals for the Federal Circuit 

05-1001,-1376 

PRIMOS, INC., 

 Plaintiff-Appellee, 

v. 

HUNTER’S SPECIALTIES, INC. and DAVID FORBES, 

 Defendants-Appellants, 

and 

WAYNE CARLTON and CARMEN FORBES, 

 Defendants. 

 Brett L. Foster, Holland & Hart LLP, of Salt Lake City, Utah, argued for plaintiffappellee. With him on the brief were L. Grant Foster and Mark A. Miller. 

 Edmund J. Sease, McKee, Voorhees & Sease, P.L.C., of Des Moines, Iowa, 

argued for defendants-appellants. With him on the brief was Jeffrey D. Harty. 

Appealed from: United States District Court for the Northern District of Iowa 

Chief Magistrate Judge John A. Jarvey 
United States Court of Appeals for the Federal Circuit 

 

05-1001, -1376 

PRIMOS, INC., 

 Plaintiff-Appellee, 

v. 

HUNTER’S SPECIALTIES, INC. and DAVID FORBES, 

 Defendants-Appellants, 

and 

WAYNE CARLTON and CARMEN FORBES, 

 Defendants. 

 _____________________ 

DECIDED: June 14, 2006 

_____________________ 

Before NEWMAN, LOURIE, and PROST, Circuit Judges. 

LOURIE, Circuit Judge.

Hunter’s Specialties, Inc. and David Forbes (collectively “Hunter’s Specialties”) 

appeal from the judgment of the United States District Court for the Northern District of 

Iowa of literal infringement, willfulness, and inducement of infringement as to U.S. 

Patent 5,520,567 and infringement under the doctrine of equivalents as to U.S. Patent 

5,415,578. Hunter’s Specialties also appeals from the court’s decision denying a 

motion for a new trial. Primos, Inc. v. Hunter’s Specialties, Inc., No. C01-004 (N.D. Iowa 

Sept. 9, 2004) (“Final Judgment”). Because we affirm the district court’s claim 

construction of the term “engaging,” we also affirm the court’s judgment of literal 
infringement of the ’567 patent. Because we conclude that the application of the 

doctrine of equivalents was proper, we affirm the court’s judgment of infringement of the 

’578 patent under the doctrine of equivalents. Because the court did not abuse its

discretion in excluding evidence, and the court’s adverse-inference jury instruction did 

not constitute prejudicial error, we affirm the court’s decision denying a new trial on

those issues. 

BACKGROUND 

This appeal involves the ’578 patent and its continuation, the ’567 patent, which 

are assigned to Primos, Inc. (“Primos”) and entitled “Game Call Apparatus.” The 

patents disclose a diaphragm mouth call that hunters use to simulate animal sounds.

Figure 1, shown below, is an embodiment of the invention: 

As depicted in that figure, the diaphragm mouth call 10 consists of a frame 18, a 

membrane 22 that vibrates to produce sound, a flexible peripheral edge 12, and a shelf

or plate 15 extending above the membrane. The diaphragm mouth call is placed 

completely within the user’s mouth, with the free-end of the membrane positioned near

the opening of the mouth. ’578 patent, col. 2, ll. 62-64. The user holds the diaphragm 

in place with his or her tongue, while forcing air to travel through a gap between the 

05-1001, -1376 2
tongue and the membrane. The air causes the membrane to vibrate and to emit a 

sound that replicates a particular animal. Id. at col. 1, ll. 31-38. The sound produced by

the call is affected by the tongue pressure applied to the membrane and the distance 

between the membrane and the roof of the mouth. Id. at col. 1, ll. 38-40. The patented 

diaphragm mouth call claims an improvement over prior mouth call devices in that the 

shelf or plate provides a constant distance above the membrane and resists upward 

pressure by the tongue. Id. at col. 2, ll. 15-26. 

Relevant to this appeal are claim 2 of the ’578 patent and claim 21 of the ’567 

patent. Claim 2 of the ’578 patent reads as follows: 

A game call apparatus to be completely inserted inside a person’s mouth 

for calling game, comprising: 

a frame; 

a membrane of material stretched over the frame; 

a flexible and moldable peripheral edge extending outwardly from 

the frame; and 

a plate having a length, the plate extending generally upward from 

the frame and over a portion of the membrane, the plate being 

differentially spaced above the portion of the membrane at various

locations along the length of the plate. 

’578 patent, col. 4, ll. 45-55 (emphases added). Claim 21 of the ’567 patent

reads as follows: 

A game call for use inside a person’s mouth, comprising:

 a U-shaped frame; 

 a yieldable reed spanning across the U-shaped frame; 

a first roof-of-mouth engaging yieldable sealing portion carried by 

the frame; 

a second roof-of-mouth engaging portion extending upwardly from 

the frame, the second portion being spaced away from the first 

portion, the first and second portions defining a predetermined 

orientation of the U-shaped frame insider the mouth relative to the 

roof of mouth. 

’567 patent, col. 6, ll. 20-32 (emphases added). 

05-1001, -1376 3
On January 24, 2001, Primos filed suit against its competitor, Hunter’s 

Specialties, alleging that Hunter’s Specialties’s accused device, known as the Tone 

Trough, infringed Primos’s patents. The accused Tone Trough is a diaphragm mouth 

call device that, among other features, contains a dome extending above the 

membrane, instead of a shelf or plate, as claimed in Primos’s patents. Primos

subsequently amended its complaint, alleging that individual defendant David Forbes

induced infringement of its patents.1

 

Primos initially moved for summary judgment of literal infringement and for a 

preliminary injunction against Hunter’s Specialties. Hunter’s Specialties filed several 

cross-motions, including for summary judgment of noninfringement, both literally and 

under the doctrine of equivalents. On July 24, 2002, the court denied all the motions

filed by both parties. In its decision, the court construed the term “plate” in claim 2 of 

the ’578 patent to mean “a structural element of relatively uniform thickness and flatness

which may also have some moderate curvature to it.” Primos v. Hunter’s Specialties, 

No. C01-004 MJM (N.D. Iowa July 24, 2002) (“Summary Judgment Order”). Relying on

that construction of the term “plate,” the court found that “reasonable minds could differ

as to the presence or absence of a ‘plate’ in the Tone Trough” and thus denied all 

summary judgment motions relating to infringement of the ’578 patent. Id. Regarding 

claim 21 of the ’567 patent, the court noted that while the term “second-roof-of-mouth

engaging portion” is not in dispute, it stated that “it is clear that this language requires

 1 The amended complaint also included allegations against individuals

Carman Forbes and Wayne Carlton for inducing infringement. The court dismissed 

Carman Forbes from the case prior to trial, and it ultimately vacated judgment against

Wayne Carlton. Thus, only David Forbes and Hunter’s Specialties remain as parties to 

this appeal. 

05-1001, -1376 4
that a portion of the claimed device . . . come into contact with the roof of the user’s

mouth while in use.” Id., slip op. at 43. The court then determined that there were 

genuine issues of material fact relating to whether the Tone Trough device operates 

when touching the roof of a user’s mouth, and therefore denied the summary judgment 

motions relating to infringement of the ’567 patent. 

Hunter’s Specialties then requested a Markman hearing to interpret the term 

“engaging” in claim 21 of the ’567 patent. On March 15, 2004, the court construed that 

term to mean to “come into contact with.” Primos v. Hunter’s Specialties, No. C01-004 

(N.D. Iowa Mar. 15, 2004) (“Claim Construction Order”). The court rejected Hunter’s 

Specialties’ construction of the term “engaging” as “interlocking,” noting that while the 

word “interlocking,” as defined in a standard dictionary, may be appropriate in the 

context of a transmission or a latch, it is not appropriate in the context of the roof of

one’s mouth. The court also observed that the specification of the ’567 patent did not

support a construction of “engaging” to mean “interlocking” because the figures in the 

patent did not provide any means with which the diaphragm mouth call could interlock in

the roof of a mouth. According to the court, it had previously interpreted “engaging” to 

mean “to come into contact with,” and it saw no reason to modify that construction. 

Hunter’s Specialties again moved for summary judgment, asserting that 

prosecution history estoppel barred the application of the doctrine of equivalents as to 

the ’578 patent in light of our intervening decision in Festo Corp. v. Shoketsu Kinzoku 

Kogyo Kabushiki Co., Ltd., 344 F.3d 1359 (Fed. Cir. 2003). The court determined that 

the term “plate” was amended during prosecution by describing it as “having a length,” 

but that that amendment did not narrow the scope of the claim because “all physical 

05-1001, -1376 5
objects have a length.” Primos v. Hunter’s Specialties, No. C01-004 MJM (N.D. Iowa 

Mar. 12, 2004) (“Prosecution History Estoppel Order”). The court also observed that the 

term “plate” was amended to require that it be “differentially spaced” above the 

membrane, which narrowed the scope of the claim. Id. According to the court, the 

subject matter surrendered by that amendment involved “objects that are not

differentially spaced above the membrane.” Because the Tone Trough contained a 

dome that was spaced above the membrane and therefore arguably did not fall within 

that surrendered area, the court denied summary judgment of no infringement under the 

doctrine of equivalents as to the ’578 patent. 

Finally, before trial, Primos filed a motion requesting that a device known as the 

Aluminum Flap Call not be introduced as evidence during trial. The court granted that 

motion, and noted in its order that, throughout discovery, Hunter’s Specialties never 

identified the Aluminum Flap Call as invalidating prior art. Primos v. Hunter’s 

Specialties, No. C01-004 MJM (N.D. Iowa Mar. 12, 2004) (“Aluminum Flap Call Order”). 

Hunter’s Specialties had sought to introduce the Aluminum Flap Call device when it

claimed it had found the device, which was approximately three months prior to trial and 

several months after discovery had closed. However, Hunter’s Specialties failed to offer 

any explanation why it could not locate the Aluminum Flap Call during discovery. In 

light of those circumstances, the court determined that allowing the Aluminum Flap Call

to be introduced as evidence during trial would result in unfair surprise to Primos, and 

thus the court granted Primos’s motion to exclude the Aluminum Flap Call as evidence. 

A jury trial commenced on March 15, 2004. In the jury instructions concerning 

inducement of infringement against individual defendants Wayne Carlton and David 

05-1001, -1376 6
Forbes, the court instructed the jury that it could consider several factors and stated that 

“the assertion of the attorney-client privilege with respect to a non-infringement opinion 

may support an inference that the withheld advice of counsel was adverse to that party.” 

As for willful infringement against Hunter’s Specialties, the court did not instruct the jury

as to an adverse inference but rather stated that the jury must consider the “totality of 

the circumstances.” After a three-and-a-half week trial, the jury found that Hunter’s

Specialties’ Tone Trough device literally infringed the ’567 patent, and infringed the ’578 

patent under the doctrine of equivalents. The jury also found that Hunter’s Specialties 

willfully infringed the ’567 patent and that David Forbes and Wayne Carlton induced

infringement of that patent. 

Hunter’s Specialties and Wayne Carlton moved for judgment as a matter of law 

(“JMOL”), arguing that the court improperly construed the term “engaging” in claim 21 of 

the ’567 patent and that the “all limitations rule” and prosecution history estoppel barred 

the application of the doctrine of equivalents as to the ’578 patent. Those defendants 

also moved for a new trial, arguing that the court erred in excluding the Aluminum Flap

Call as evidence, and that the court’s adverse-inference instruction resulted in 

prejudicial error. The court denied the motion for JMOL and the motion for a new trial.

Primos v. Hunter’s Specialties, No. C01-004 (N.D. Iowa Mar. 31, 2005). (“Post-Trial 

Order”). In its decision, the court first reaffirmed its construction of the claim term 

“engaging” in claim 21 of the ’567 patent, noting that it had addressed the same issue in 

previous decisions. The court next determined that the “all limitations rule” did not

preclude the application of the doctrine of equivalents for the ’578 patent, reasoning that 

the only disputed term was “plate” in claim 2, and that determining that a dome was

05-1001, -1376 7
equivalent to a plate did not vitiate that claim limitation. The court also held that 

prosecution history estoppel did not prevent the application of the doctrine of

equivalents as to the ’578 patent because the Tone Trough did not fall within the area 

surrendered during prosecution. In addition, the court denied Hunter’s Specialties’s

motion for a new trial, reaffirming its prior decision that the Aluminum Flap Call device

could not be introduced as invalidating prior art because it was produced after the 

period for discovery had closed. Although the court determined that its “adverse 

inference” instruction to the jury was not in error, the court later vacated judgment 

against Wayne Carlton, the only defendant who had asserted the attorney-client

privilege, in light of our decision in Knorr-Bremse Systeme Fuer Nutzfahrzeuge GMBH

v. Dana Corp., 383 F.3d 1337 (Fed. Cir. 2004) (en banc). 

Hunter’s Specialties timely appealed to this court, and we have jurisdiction 

pursuant to 28 U.S.C. § 1295(a)(1). 

DISCUSSION 

We review a district court’s denial of a motion for JMOL de novo by reapplying 

the JMOL standard. Markman v. Westview Instruments, Inc., 52 F.3d 967, 975 (Fed.

Cir. 1995) (en banc). We also review the legal standards that the jury applied in

reaching its verdict to determine whether they were correct as a matter of law. Id. at 

975. JMOL is appropriate when “there is no legally sufficient evidentiary basis for a 

reasonable jury to find for that party on that issue.” Fed. R. Civ. P. 50(a)(1). The denial 

of a motion for a new trial is an issue not unique to patent law; thus, we apply the law of 

the regional circuit in which the district court sits—in this case, the Eighth Circuit. In the 

05-1001, -1376 8
Eighth Circuit, the decision to deny a motion for a new trial is reviewed under an abuse 

of discretion standard. Blair v. Wills, 420 F.3d 823, 829 (8th Cir. 2005). 

I. Claim Construction

The question of literal infringement of claim 21 of the ’567 patent turns entirely on 

the district court’s construction of the term “engaging.” Claim construction is a question 

of law reviewed de novo. Cybor Corp. v. FAS Techs., Inc. 138 F.3d 1448, 1454-56 (Fed.

Cir. 1998) (en banc). Hunter’s Specialties argues that the court erred in construing the 

term “engaging” in the phrase “second roof-of-mouth engaging yieldable sealing portion” 

to mean “to come into contact with.” According to Hunter’s Specialties, the proper

construction of the term “engaging” is “sealing” or “interlocking.” As support for its 

construction, Hunter’s Specialties notes that claim 21 uses the word “engaging” to 

describe a seal created between the edge of the frame and the roof of the user’s mouth.

Also, Hunter’s Specialties observes that the specification describes the edge as

“sealing” against the roof of a mouth. In addition, Hunter’s Specialties finds support for

its construction in a dictionary definition that describes “engaging” as “to come together

and interlock.” Hunter’s Specialties points out that this definition is consistent with the 

way the term is used throughout the patent. 

Primos responds that the district court correctly construed “engaging” as “to 

come into contact with.” According to Primos, the intrinsic evidence does not support 

the selective dictionary definition put forth by Hunter’s Specialties. In particular, the

claims use both terms, “engaging” and “sealing,” and thus each term is presumed to 

have a distinct meaning. Also, Primos asserts that to construe “engaging” as “sealing”

or “interlocking” would exclude a preferred embodiment of the patent because the 

05-1001, -1376 9
figures in the patent show the membrane as not interlocking with the roof of a mouth. In 

addition, Primos observes that while “interlocking” might be an appropriate construction 

of “engaging” for an invention relating to mechanical machinery with gears, it is not

appropriate in the context of diaphragm mouth calls. 

We agree with Primos that the district court correctly construed the term 

“engaging” to mean “to come into contact with.” As this court explained in Phillips v. 

AWH Corp., we ordinarily construe claim terms to have their customary meaning as

understood by a person of ordinary skill in the art. 415 F.3d 1303, 1312-17 (Fed. Cir. 

2005) (en banc). In ascertaining the ordinary and customary meaning of a claim term, a 

court’s primary focus should be on the intrinsic evidence of record, viz., the claims, the 

specification, and, if in evidence, the prosecution history. Id. Starting with the language 

of claim 21, the terms “engaging” and “sealing” are both expressly recited in the claim 

and therefore “engaging” cannot mean the same thing as “sealing”; if it did, one of the 

terms would be superfluous. 

Turning to the specification, although the word “engaging” is not expressly

mentioned in the specification, figures 1 and 3 aid our understanding of that term. 

Figure 3, as depicted below, shows a call device positioned in a user’s mouth. 

05-1001, -1376 10
As shown in the figure above, there are several points of contact between the roof of a 

user’s mouth (the top striped structure in the figure above) and the diaphragm mouth 

call—one such point is with the plate 24 and another is with the peripheral edge of the 

frame 12. That figure shows the plate touching the roof of the mouth, but does not

reveal an interlocking relationship because there is no depicted means from which the 

frame can “interlock” with the roof of a user’s mouth. The figure therefore supports a 

construction of “engaging” as to “come into contact with,” while discouraging a 

construction of “interlocking.” While we are mindful that we cannot import limitations 

from the preferred embodiments into the claim, we also should not normally interpret a 

claim term to exclude a preferred embodiment. See Burke, Inc. v. Bruno Indep. Living 

Aids, Inc., 183 F.3d 1334, 1341 (Fed. Cir. 1999). Interpreting “engaging” to mean 

“interlocking” would exclude the embodiment shown in the figure and is not consistent 

with the rest of the specification which does not suggest an interlocking relationship 

between the roof of a mouth and the mouth call.2

 We therefore agree that the district 

court’s construction of the term “engaging” to mean “to come into contact with” is

supported by the intrinsic record and is correct. 

II. Doctrine of Equivalents

Hunter’s Specialties challenges the application of the doctrine of equivalents on 

the ground that prosecution history estoppel applies to the term “plate.” Hunter’s

Specialties specifically asserts that amendments to the term “plate” narrowed the scope 

of the claim and were made for reasons relating to patentability. According to Hunter’s

Specialties, prosecution history estoppel therefore barred the doctrine of equivalents for 

 2 We do not discuss the prosecution history here because it is not relevant 

to the construction of the term “engaging.” 

05-1001, -1376 11
that claim term. Primos responds that the district court properly applied the doctrine of

equivalents. It reasons that the first amendment made to the term “plate”—that it 

include a “length”—did not narrow the scope of the claim. As to the second amendment 

made to the term “plate”—that it be “differentially spaced” above the membrane—that 

amendment bears no more than a tangential relationship to the accused Tone Trough. 

In particular, Primos contends that the territory surrendered by that amendment consists

of objects that are not differentially spaced above the membrane. Because the accused 

device’s “dome” is differentially spaced above the membrane, Primos asserts that the 

“differentially spaced” amendment does not pertain to the disputed element in the 

accused device and it is therefore merely tangential to the accused device. According 

to Primos, prosecution history estoppel thus does not apply to prevent the application of 

the doctrine of equivalents here. 

We agree with Primos that the district court correctly determined that prosecution 

history estoppel does not apply here to preclude the application of the doctrine of

equivalents. 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. 

The term “plate” in claim 2 of the ’578 patent was amended in two ways: (1) by

requiring that it have a “length” and (2) by adding the limitation that the plate be 

05-1001, -1376 12
“differentially spaced” above the membrane. The district court correctly recognized that 

the addition of the term “length” did not narrow the scope of the claim because every 

physical object has a length. The district court also determined that adding the 

limitation that the plate be “differentially spaced” above the membrane did narrow the 

scope of the claim, and the court assumed that the reason for the amendment was a 

substantial one relating to patentability. We agree with the district court, however, that 

the territory surrendered by the “differentially spaced” amendment comprises plates that 

are not differentially spaced above the membrane. That conclusion is consistent with 

the prosecution history. The patentee added the “differentially spaced” limitation to 

distinguish the diaphragm mouth call from a prior art device that consisted of a shelf-like 

structure positioned on top of the membrane without any spacing. The accused device, 

however, includes a dome that is spaced above the membrane. 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. 

Hunter’s Specialties also argues that the court should not have allowed the 

application of the doctrine of equivalents because, by doing so, the claim limitation 

“plate” in claim 2 of the ’578 patent was vitiated. According to Hunter’s Specialties, the 

court’s construction of the term “plate” requires a specific structure “of relatively uniform

thickness and flatness which may also have some moderate curvature to it. Hunter’s

Specialties asserts that allowing a “dome” to be considered an equivalent to a “plate”

would eliminate that limitation from the claim. Primos responds that the “all limitations 

rule” is not applicable to the circumstances in this case. According to Primos, the term 

05-1001, -1376 13
“plate” does not convey a definitive, geometric shape or structure, and thus that claim

limitation was not vitiated. Primos asserts that the district court properly allowed the jury 

to consider whether a “dome” was equivalent to a “plate” and that in doing so, no claim

limitation was eliminated. 

We agree with Primos that the application of the doctrine of equivalents was not

improper in this case. Under the doctrine of equivalents, “a product or process that 

does not literally infringe upon [sic] the express terms of a patent claim may 

nonetheless be found to infringe if there is ‘equivalence’ between the elements of the 

accused product or process and the claimed elements [sic] of the patented invention.”

Warner-Jenkinson Co., Inc. v. Hilton Davis Chem. Co., 520 U.S. 17, 21 (1997) (citation 

omitted). The “all limitations rule” restricts the doctrine of equivalents by preventing its

application when doing so would vitiate a claim limitation. Warner-Jenkinson, 520 U.S. 

at 29 (stating that the doctrine of equivalents cannot be applied broadly so as to 

“effectively eliminate that [claim] element in its entirety”); Lockheed Martin Corp., 324 

F.3d at 1321 (“[I]f a court determines that a finding of infringement under the doctrine of

equivalents ‘would entirely vitiate a particular claim element,’ then the court should rule 

that there is no infringement under the doctrine of equivalents.” (citation omitted)). 

On appeal, Hunter's Specialties argues that we should reverse the jury’s finding 

of equivalence because the substitution of the accused dome for the claimed “plate” 

would vitiate the “plate” limitation and thereby violate the all limitations rule. As the 

district court recognized, Hunter’s Specialties is essentially contending that there can be 

no equivalent to 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

05-1001, -1376 14
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.” Freedman Seating Co. v. Am.

Seating Co., 420 F.3d 1350, 1359 (Fed. Cir. 2005) (citations omitted). 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. Noting that Hunter’s Specialties has not challenged whether the 

jury’s finding is supported by substantial evidence, we affirm the jury’s finding that the 

accused dome is equivalent to the claimed “plate.” 

III. Exclusion of Evidence

Hunter’s Specialties next argues that the district court abused its discretion in 

excluding a prior art device, the Aluminum Flap Call, from evidence because admitting it 

would have resulted in prejudicial surprise. According to Hunter’s Specialties, even 

though the device itself was not located until shortly before trial began, Primos was 

aware of it as being potential prior art throughout discovery. For example, Hunter’s

Specialties asserts that defendant Wayne Carlton was extensively questioned by

Primos on the Aluminum Flap Call device. Hunter’s Specialties also asserts that Primos 

waited until shortly before the commencement of trial to claim prejudicial surprise, even 

though it knew about the device much earlier. In addition, Hunter’s Specialties argues

that there is a strong public policy in favor of allowing the Aluminum Flap Call as

evidence because the public interest requires consideration of any invalidating prior art 

device. 

05-1001, -1376 15
Primos responds that the district court properly excluded the Aluminum Flap Call 

because Hunter’s Specialties never identified that device as potentially invalidating prior

art during discovery. In addition, Primos asserts that the defendants did not provide an 

explanation as to why they could not locate that device during discovery. According to 

Primos, to permit the Aluminum Flap Call to be introduced as evidence during trial, after 

years of discovery during which that device was not identified, would result in prejudicial 

surprise. Also, although the Aluminum Flap Call may have been mentioned during

discovery, its origin could not be authenticated, and the testimony revealed that the 

prototypes were experimental in nature. Thus, there was no reason for Primos to 

believe that the Aluminum Flap Call was prior art and would be introduced as evidence. 

We agree with Primos that the district court did not abuse its discretion in 

excluding the Aluminum Flap Call from evidence. The record reflects that the Aluminum

Flap Call was not located until after discovery had closed. Moreover, although the 

Aluminum Flap Call may have been mentioned during discovery, it was never identified 

to the court as an invalidating prior art device. The district court prevented Hunter’s

Specialties from introducing the Aluminum Flap Call into evidence because it “did not 

demonstrate diligence in attempting to locate the call during discovery” and because

during discovery Hunter’s Specialties did not assert that it was claiming the Aluminum

Flap Call as invalidating prior art. That determination was not an abuse of discretion. It

was well within the district court’s province to determine that because the Aluminum

Flap Call was not identified as potential prior art until after discovery had closed and 

shortly before trial commenced, it would then be unfair to permit its introduction into

evidence. 

05-1001, -1376 16
We reject Hunter’s Specialties’ argument that policy concerns should override the 

district court’s decision to exclude the Aluminum Flap Call as evidence. First, and most 

importantly, the court never determined whether the Aluminum Flap Call was in fact

invalidating prior art, and the parties dispute whether the device was in public use—it

was asserted that its use was experimental and occurred only in Canada. Thus, the 

Aluminum Flap Call may in fact not have been invalidating prior art at all. Second, as

the district court pointed out, the purpose of discovery is to enable parties to obtain the 

factual information needed to prepare their cases for trial. The district court must

therefore consider the “unfair and prejudicial surprise” to a party that may result from 

allowing evidence to be presented during trial. See ATD Corp. v. Lydall, Inc., 159 F.3d 

534, 551 (Fed. Cir. 1998) (stating that the purpose of both the Federal Rules of Civil 

Procedure and 35 U.S.C. § 282 is to prevent unfair and prejudicial surprise and not to

permit last-minute production of evidence). The district court determined that Hunter’s 

Specialties had ample opportunity to introduce the Aluminum Flap Call during the two 

and a half year discovery phase. Because it did not do so, the district court was entitled 

to decide that Hunter’s Specialties may not then introduce disputed evidence beyond 

the time allotted for discovery. 

IV. Adverse-Inference Jury Instruction

Finally, Hunter’s Specialties asserts that under Knorr-Bremse, 383 F.3d at 1337,

the district court erred in instructing the jury that it could draw an adverse-inference from

an opinion withheld due to the assertion of the attorney-client privilege. Although

Hunter’s Specialties recognizes that the only defendant to assert the attorney-client

privilege was Wayne Carlton, it argues that the adverse-inference jury instruction 

05-1001, -1376 17
prejudiced all defendants because the infringement claim involved all defendants and 

was tried to one jury. Primos responds that the court vacated the judgment against

Wayne Carlton, the only individual who asserted the attorney-client privilege and

therefore the only person who was potentially prejudiced by the jury instruction. Primos

points out that Hunter’s Specialties waived the attorney-client privilege and thus was not

affected by the adverse jury instruction. In addition, Primos contends that Hunter’s

Specialties did not present any evidence on how it was prejudiced by the jury’s 

instruction. 

We agree with Primos that the jury instruction did not prejudice Hunter’s 

Specialties. A party seeking to alter a judgment based on erroneous jury instructions 

must establish that “those instructions were legally erroneous,” and that “the errors had 

prejudicial effect.” Advanced Display Sys., Inc. v. Kent State Univ., 212 F.3d 1272, 

1281 (Fed. Cir. 2000). Legal error in an erroneous jury instruction is prejudicial when it

is “inconsistent with substantial justice.” Fed. R. Civ. P. 61. The jury’s instruction for 

inducement of infringement against individual defendants David Forbes and Wayne 

Carlton provided that “the assertion of the attorney-client privilege with respect to a noninfringement opinion may support an inference that the withheld advice of counsel was

adverse to that party.” That jury instruction thus permitted an adverse inference to be 

drawn against the party that asserted the attorney-client privilege. The only individual 

who asserted the attorney-client privilege, however, was Wayne Carlton, and the court

vacated the judgment of inducement of infringement against him. The only individual 

therefore potentially prejudiced by the adverse-inference instruction was Wayne 

Carlton, not Hunter’s Specialties. In addition, in the jury’s instruction as to willful

05-1001, -1376 18
infringement against individual defendant Hunter’s Specialties, the express adverse 

inference language was absent. Rather, the instruction stated that the jury must 

consider the totality of the circumstances and may rely on a number of factors to 

support a finding of willfulness. There was therefore no adverse-inference instruction as 

to willfulness against Hunter’s Specialties. Thus, we conclude that the jury’s instruction 

was not legally erroneous and did not result in prejudicial error against either individual 

defendants Hunter’s Specialties or David Forbes. 

We have considered Hunter’s Specialties other arguments and find them to be 

unpersuasive. 

CONCLUSION 

Because the court properly construed the term “engaging,” we affirm the court’s 

judgment of literal infringement. Because the claim term “plate” is a structure that was 

not vitiated by substitution of a dome, we affirm the court’s conclusion that applying the 

doctrine of equivalents was not improper. Also, because the amendment was merely

tangential to the contested element in the accused device, we affirm the court’s 

determination that prosecution history estoppel did not preclude the application of the 

doctrine of equivalents. Finally, because the court did not abuse its discretion in 

excluding the Aluminum Flap Call as evidence and because its adverse-inference 

instruction did not constitute prejudicial error, we affirm the court’s decision denying a

new trial. 

AFFIRMED. 

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