                           PUBLISHED

UNITED STATES COURT OF APPEALS
                FOR THE FOURTH CIRCUIT


UNITED STATES OF AMERICA,              
                 Plaintiff-Appellee,
                 v.                             No. 00-4926
MICHAEL BARILE,
              Defendant-Appellant.
                                       
           Appeal from the United States District Court
            for the District of Maryland, at Greenbelt.
             Alexander Williams, Jr., District Judge.
                            (CR-99-225)

                      Argued: December 6, 2001

                       Decided: April 18, 2002

      Before WILKINS and WILLIAMS, Circuit Judges, and
              HAMILTON, Senior Circuit Judge.



Remanded with instructions by published opinion. Judge Williams
wrote the opinion, in which Judge Wilkins and Senior Judge Hamil-
ton joined.


                            COUNSEL

ARGUED: Joseph Sedwick Sollers, III, KING & SPALDING,
Washington, D.C., for Appellant. Bryan Edwin Foreman, Assistant
United States Attorney, Greenbelt, Maryland; Steven Neil Gersten,
Trial Attorney, Office of Consumer Litigation, UNITED STATES
DEPARTMENT OF JUSTICE, Washington, D.C., for Appellee. ON
2                      UNITED STATES v. BARILE
BRIEF: Eugene M. Pfeifer, Jeffrey S. Bucholtz, KING & SPAL-
DING, Washington, D.C., for Appellant. Stephen M. Schenning,
United States Attorney, Greenbelt, Maryland, for Appellee.


                              OPINION

WILLIAMS, Circuit Judge:

   Michael Barile was convicted of making materially false state-
ments to the Federal Food and Drug Administration (FDA), in viola-
tion of 18 U.S.C.A. §§ 1001 and 2. Barile challenges his conviction
on the grounds that the district court erred by excluding impeachment
evidence and by not permitting opinion testimony regarding the mate-
riality of Barile’s false statements. Because we conclude that the dis-
trict court erred in its determination that prior statements of a key
government witness were consistent, we remand for further proceed-
ings. We discuss each challenge in turn.

                                   I.

   Barile and three co-workers, Haryash Gugnani, Amrik Sikand, and
Theodore Milo, were indicted by a grand jury in May 1999. All four
defendants were employed by the Patient Monitoring Division of
Datascope Corporation, a manufacturer of medical devices. Gugnani
was president of Patient Monitoring, Sikand was vice president of
operations, and Milo was director of engineering. Both Sikand and
Milo reported to Gugnani. Barile, director of quality assurance and
regulatory affairs, reported to Sikand. Datascope manufactures and
markets a diverse range of medical devices, including cardiac moni-
tors. A cardiac monitor measures the electric current traversing the
heart and displays the data as an electrocardiogram (ECG). Cardiac
monitors also measure numerous other vital signs. For example, the
Datascope Passport Monitor, released in 1991, in addition to function-
ing as an ECG, also records heart rate, invasive blood pressure, non-
invasive blood pressure, pulse rate, pulse oximetry, temperature, and
respiration rate. While each cardiac monitor has multiple functions,
it operates as a single unit, taking simultaneous readings of many vital
signs. Datascope’s cardiac monitors are complex, software-driven
devices that are continuously being improved.
                       UNITED STATES v. BARILE                        3
   Under § 510(k) of the Federal Food, Drug, and Cosmetic Act,
when Datascope makes an enhancement it must notify the FDA prior
to marketing the product. See 21 U.S.C.A. § 360(k) (West 1999). The
pre-market notification, known as a 510(k) submission, must demon-
strate that the medical device is "substantially equivalent" to a device
that is already on the market. See 21 U.S.C.A. § 360c(f)(1)(A)(ii)
(West 1999). If a medical device is not substantially equivalent to a
device already on the market, it is subject to the more rigorous pre-
market approval process. See 21 U.S.C.A. § 360e(c) (West 1999). The
trial below stemmed from allegedly false statements made on 510(k)
submissions for three of Datascope’s cardiac monitors.

   First, on December 1, 1992, Datascope made a 510(k) submission
for a 6000 Point of View Monitor (Point of View). This device was
similar to the original Passport monitor, released in 1991, but added
an "ST segment," which measures marginal changes in portions of the
ECG to detect arrhythmic heartbeat patterns. This new component,
which was a fully tested and approved feature, was purchased from
a company called PCI. The FDA cleared the Point of View monitor
on August 6, 1993, and Datascope began distributing it in March
1994. The second 510(k) submission, on January 11, 1994, was for
an advanced version of the Point of View, called a 6000 Point of
View Monitor with Cardiac Output (Point of View with Cardiac Out-
put). The cardiac output component enhanced the Point of View mon-
itor by adding a means of measuring the flow of blood through the
heart. This submission later was withdrawn by Datascope. The third
510(k) submission was filed on May 31, 1994, and related to a moni-
tor called Passport with ST. This monitor added the ST segment,
which had already been incorporated into the Point of View, to its
existing Passport monitor. This 510(k) submission also was with-
drawn by Datascope.

   The indictment charged Barile, Gugnani, Sikand, and Milo on four
different counts related to the 510(k) submissions described above.
Count one charged all defendants with conspiracy to defraud the FDA
by making false statements in 510(k) submissions for all three moni-
tors, a violation of 18 U.S.C.A. § 371 (West 2000). Count two
charged all defendants except Milo with making false statements on
510(k) submissions for the Passport with ST monitor, in violation of
18 U.S.C.A. §§ 1001 and 2 (West 2000). Counts three and four
4                      UNITED STATES v. BARILE
accused all defendants except Milo of violating 21 U.S.C.A.
§§ 331(a) and 333(a)(2) (West 2000), and 18 U.S.C.A. § 2 (West
2000), by marketing an adulterated and misbranded medical device,
the Point of View monitor. After a five-week trial, the jury acquitted
Gugnani, Sikand, and Milo on all counts and Barile on counts one,
three, and four. The jury convicted Barile on count two, which
charged specifically that Barile represented in a 510(k) submission
that a completed Passport with ST existed and that testing had been
conducted on such a completed device when he knew that no such
completed device existed.

   Barile appeals from his conviction, challenging the district court’s
exclusion of impeachment evidence and expert testimony. We exam-
ine each challenge in turn, reviewing both of the district court’s rul-
ings for abuse of discretion. See United States v. Gravely, 840 F.2d
1156, 1163 (4th Cir. 1988) ("A district court’s determination that a
witness’ prior statements are not inconsistent with trial testimony will
not be reversed absent an abuse of discretion."); United States v. Har-
ris, 995 F.2d 532, 534 (4th Cir. 1993) ("The exclusion of expert testi-
mony under Rule 702 is within the sound discretion of the trial
judge."). Under this standard, "[a] district court by definition abuses
its discretion when it makes an error of law." United States v. Stitt,
250 F.3d 878, 896 (4th Cir. 2001) (internal quotation omitted).

                                  II.

   Barile first challenges the district court’s exclusion of documents
that he offered for the purpose of impeaching Marion Kroen, a wit-
ness for the Government. The documents with which Barile sought to
impeach Kroen were created by the FDA’s Office of Criminal Investi-
gation (OCI) during its inquiry into the fraudulent statements in
Datascope’s 510(k) submission for the Point of View monitor. Specif-
ically, Barile sought to introduce statements reflected in a Memoran-
dum of Meeting, which detailed a July 26, 1995 meeting between
OCI and FDA’s Office of Device Evaluation (ODE) regarding the
significance of the false statements, and a Report of Investigation,
summarizing the OCI’s investigation (collectively, the FDA docu-
ments). Our review of the record indicates that the district court ruled
that the proffered impeachment evidence was not specifically incon-
sistent with Kroen’s testimony. (J.A. at 531.) Moreover, the district
                        UNITED STATES v. BARILE                          5
court concluded that Barile was attempting to admit the documents to
reveal that after the July 26, 1995 meeting, the FDA decided to end
its investigation of Datascope’s 510(k) submissions, a fact that the
district court, before trial, determined to be irrelevant. (J.A. at 529.)
To analyze Barile’s challenge to the exclusion of this impeachment
evidence, we first must set forth the relevant points of dispute at trial.

   At trial, Barile did not dispute that the tests reflected in the 510(k)
submission for the Passport with ST were not conducted on a com-
pleted device. Instead, he asserted that any representation to the con-
trary on the 510(k) submission was not material. Barile contended
that it is industry practice to make a 510(k) submission while a medi-
cal device is still being developed and therefore "[t]esting on parts of
the device, which is known as component testing, is absolutely
acceptable." (J.A. at 157-58.) Barile admitted that the tests were per-
formed on components and, as Barile’s counsel pointed out at oral
argument, there was no allegation in count two that false test data
were submitted, only that the 510(k) submission for the Passport with
ST falsely represented that it reflected testing of a "completed" car-
diac monitor. Falsely representing on a 510(k) submission that a com-
pleted medical device exists and purporting that tests were run on the
completed device, when in fact they were conducted on the individual
components, Barile argued, are not materially false statements or rep-
resentations as required under 18 U.S.C.A. § 1001, which provides,
in pertinent part, that "whoever, in any matter within the jurisdiction
of the executive, legislative, or judicial branch of the Government of
the United States, knowingly and willfully . . . makes any materially
false, fictitious, or fraudulent statement or representation . . . shall be
fined under this title or imprisoned not more than 5 years, or both."

   The Government, on the other hand, asserted that component test-
ing is inappropriate for cardiac monitors. The key evidence support-
ing the Government’s contention was the testimony of Marian Kroen,
who works in the ODE and reviewed Datascope’s 510(k) submission
for the Passport with ST. When asked at trial whether the FDA would
grant a 510(k) clearance based on component testing, she responded
that "[g]enerally [component testing would suffice] when the compo-
nents operate in a vacuum or don’t have to talk to each other, like
don’t have this computer connection where they have to talk to each
other and acknowledge each other’s signals and handshake and pass
6                      UNITED STATES v. BARILE
data." (J.A. at 516.) She went on to say that "[i]f the components can
operate without each other, in a vacuum, then we can qualify them
based on component testing. If they have to be integrated and operate
as a unit, then it has to be tested as a unit." (J.A. at 516.) Kroen fur-
ther testified that the multiple functions of cardiac machines are inte-
grated and operate as a unit. (J.A. at 503-05.) Thus, according to
Kroen’s testimony, cardiac machines cannot be qualified based on
component testing.

   On cross-examination, Barile attempted to impeach Kroen’s testi-
mony with the FDA documents, which included the following state-
ments regarding Datascope’s Point of View cardiac machine: "ODE
representatives indicated in a 510(k) submission it is acceptable to
provide information resulting from component testing, prototype test-
ing, and computer algorithms," (J.A. at 63), and "Marion Kroen,
reviewer for the 6000 Point of View monitor, indicated no informa-
tion presented at the meeting would have caused her to reconsider her
original recommendation that the 6000 Point of View Monitor be con-
sidered substantially equivalent." (J.A. at 67.) Kroen was one of three
ODE representatives at the meeting.

                                   A.

   Rule 613(b), which governs the admissibility of extrinsic evidence
of a prior inconsistent statement by a witness, "first requires that a
prior statement be inconsistent." United States v. Young, 248 F.3d
260, 267 (4th Cir. 2001). A prior statement is inconsistent if it, "taken
as a whole, either by what it says or by what it omits to say affords
some indication that the fact was different from the testimony of the
witness whom it sought to contradict." United States v. Gravely, 840
F.2d 1156, 1163 (4th Cir. 1988) (internal citation omitted); Wein-
stein’s Federal Evidence § 613.04[1] (2d ed. 2001) ("Any statement
is inconsistent if under any rational theory it might lead to any rele-
vant conclusion different from any other relevant conclusion resulting
from anything the witness said.").

   In this case, the district court ruled that the prior statements were
not inconsistent for purposes of Rule 613(b). (J.A. at 537 ("I have not
heard anything specific by way of an inconsistent position taken by
this woman to justify any impeachment.").) The proffered prior state-
                       UNITED STATES v. BARILE                         7
ments indicate that "it is acceptable to provide information resulting
from component testing, prototype testing, and computer algorithms"
on a 510(k) submission for an integrated cardiac monitor,1 (J.A. at
63), and that Kroen did not "reconsider her original recommendation
that the 6000 Point of View Monitor be considered substantially
equivalent" after learning that its 510(k) submission contained test
results from component testing. (J.A. at 67.) At trial, however, Kroen
testified that component testing would not be accepted for devices
that operate as integrated units and that cardiac machines were such
units. The prior statement and the trial testimony, therefore, result in
starkly distinct conclusions regarding the propriety of component test-
ing for purposes of Barile’s 510(k) submission. Kroen testified at trial
that component testing is never appropriate for integrated cardiac
monitors, yet the FDA documents state that component testing is
appropriate for such devices. This inconsistency in plain terms is so
palpable as to surpass the threshold for admissibility under Rule 613.
See Gravely, 840 F.2d at 1163 ("To be received as a prior inconsistent
statement, the contradiction need not be in plain terms."). Thus, the
district court erred by excluding the statements under Rule 613.2

   Although we conclude that the prior inconsistent statements con-
cerning component testing are admissible under Rule 613(b), our
inquiry does not end because, "even if all the foundational elements
of Rule 613 are met, a district court is not unequivocally bound to
admit any or all extrinsic evidence of a prior inconsistent statement."
Young, 248 F.3d at 268. "Rather, a district court may still exercise its
discretion to exclude such evidence [under Federal Rule of Evidence
403] when its ‘probative value is substantially outweighed by the dan-
ger of unfair prejudice, confusion of the issues, or misleading the jury,
or by considerations of undue delay, waste of time, or needless pre-
  1
     Although this statement was made in the course of investigating the
510(k) submission for the Point of View, the parties have failed to iden-
tify any material distinction whatsoever between the Point of View car-
diac machine and the Passport ST cardiac machine for purposes of the
propriety of component testing on each.
   2
     Another foundational element under 613(b) is that the inconsistent
statement must have been made by the witness. We discuss the Govern-
ment’s contention that the statements in the FDA Documents do not
belong to Kroen in part II.B, infra.
8                      UNITED STATES v. BARILE
sentation of cumulative evidence.’" Id. (quoting Fed. R. Evid. 403).
When we review a district court’s decision to exclude evidence under
Rule 403, we are required to "look at the evidence in a light most
favorable to its proponent, maximizing its probative value and mini-
mizing its prejudicial effect." United States v. Russell, 971 F.2d 1098,
1106 (4th Cir. 1992) (citation omitted).

   Here, the district court evaluated the effect of Rule 403 with
respect to the admissibility of the FDA documents and ruled that prior
inconsistent statements within the documents would be admissible
under Rule 403, except to the extent that the inconsistent statements
revealed the FDA’s decision to end its investigation of the Datascope
Point of View monitor. (J.A. at 123-24 ("I’m not going to restrict the
defense in their cross-examination of witnesses who may take the
stand and who may be making a statement in court that is inconsistent
with their previous position on an issue, if it is. The government cer-
tainly can’t hide that.").) The district court then concluded that
Barile’s proffer was "simply an indirect way to get before the jury a
preliminary determination made by the Food and Drug Administra-
tion." (J.A. at 537.) This analysis is untenable, however, because the
prior statements indicating that component testing is appropriate on
a cardiac machine do not reveal the FDA’s decision to abandon its
investigation of the Datascope Point of View Monitor.

   To the extent that the district court excluded Kroen’s prior state-
ments on the ground that they revealed her opinion on materiality,
(J.A. at 529 ("materiality is something the jury has to determine")),
the district court erred because its determination was based on a faulty
premise. Kroen’s statements do not constitute a legal conclusion on
whether any misrepresentations in the 510(k) submission were mate-
rial. None of her statements in the FDA documents give an opinion
on what constitutes a violation of 18 U.S.C.A. § 1001, or even what
is legally required for a 510(k) submission. Instead, her statements
provide evidence of what information she, as a 510(k) reviewer, con-
sidered significant. (J.A. at 67 ("Marion Kroen, reviewer for the 6000
Point of View monitor, indicated no information presented at the
meeting would have caused her to reconsider her original recommen-
dation that the 6000 Point of View Monitor be considered substan-
tially equivalent.")); (id. ("ODE representatives further advised the
fact that test results and software validation performed on components
                        UNITED STATES v. BARILE                          9
was represented as being performed on a completed device in and of
itself was not a significant misrepresentation.").) Evidence of what
information a reviewer of 510(k) submissions deems important does
not constitute opinion testimony on the ultimate issue of materiality.
See United States v. Kingston, 971 F.2d 481, 486 (10th Cir. 1992)
("Government witnesses are permitted . . . to testify as to whether cer-
tain truths, if known, would have influenced their decisionmaking for
purposes of 18 U.S.C. § 1001."). Further, such evidence will greatly
assist the jury in its determination of whether any false statements
were material. See Kungys v. United States, 485 U.S. 759, 770 (1988)
("[A] concealment or misrepresentation is material if it has a natural
tendency to influence, or was capable of influencing, the decision of
the decisionmaking body to which it was addressed."). Moreover,
inconsistent statements made by the Government’s witness regarding
what information she deems important when reviewing 510(k) sub-
missions is far too probative to be outweighed by any danger of unfair
prejudice or confusion. Kroen’s statements in the FDA documents
regarding what information in the 510(k) submission she deemed
important, therefore, cannot be excluded on the basis that they invade
the province of the jury.

   Having concluded that the prior statements are inconsistent and
that they are not excludable under the district court’s Rule 403 analy-
sis, we conclude that the district court should have admitted the prior
statements as impeachment evidence, provided proper foundation can
be established.3
  3
   The Government asserts that any error that occurred when the district
court excluded the impeachment evidence was harmless because Barile
was able to ask Kroen about the propriety of component testing in gen-
eral. (J.A. at 538.) A violation of the rules of evidence is harmless if it
does not affect a "substantial right" of a party. See Ross v. Saint Augus-
tine’s Coll., 103 F.3d 338, 342 (4th Cir. 1996). Barile’s attorney was not
permitted to phrase a question that would reveal the inconsistency
between Kroen’s testimony and her prior statements. Kroen testified that
component testing is only acceptable for nonintegrated devices, but in
her prior statements she indicated that component testing was acceptable
for integrated cardiac monitors. Because Kroen’s testimony at trial could
lead a reasonable juror to conclude that Barile’s 510(k) submission
included a material falsification and because she was the reviewer of the
10                      UNITED STATES v. BARILE
                                   B.

   Only prior inconsistent statements made by the witness are admis-
sible as impeachment evidence under Rule 613(b). The Government
argues that, even assuming the prior statements concerning compo-
nent testing are inconsistent and are otherwise admissible under Rule
403, the statements cannot be used to impeach because they are the
statements of a third party, OCI, which were not adopted by Kroen.
See United States v. Saget, 991 F.2d 702, 710 (11th Cir. 1993) ("[W]e
conclude that a witness may not be impeached with a third party’s
characterization or interpretation of a prior oral statement unless the
witness has subscribed to or otherwise adopted the statement as his
own."). The record lacks evidence upon which to determine whether
Kroen has adopted the statements or whether they can be otherwise
attributed to her because the Government did not object at trial to the
admissibility of the prior statements on this ground.4 Thus, prior to
conducting a new trial, the district court must determine whether the
statements are reasonably attributable to Kroen.5 See United States v.

510(k) submission at issue, her testimony is key evidence of materiality.
The proffered impeachment evidence called into question the credibility
of Kroen’s conclusions about the propriety of component testing in a
510(k) submission for an integrated cardiac monitor, the very issue criti-
cal to Barile’s conviction. We therefore cannot conclude that the district
court’s error in precluding this impeachment evidence was harmless.
   4
     Although the Government, in response to Barile’s Motion for Release
Pending Appeal, contended that "Barile was unable to lay the proper
foundation to have the document admitted into evidence [because Kroen]
testified that she was unfamiliar with the document and that she had
never seen the document before," (Appellee’s Opposition to Appellant’s
Motion for Release Pending Appeal at 6), our review of the trial tran-
scripts fails to reveal that Barile was afforded an opportunity to lay the
foundation for these materials. Indeed, the Government fails to provide
any citation to support its version of Barile’s cross-examination of
Kroen. (Appellee’s Opposition to Appellant’s Motion for Release Pend-
ing Appeal at 6, 8.)
   5
     Despite our conclusion that a remand is appropriate to develop the
foundation of the prior statement, we analyzed the exclusion of the state-
ment on the ground given by the district court in Section II.A., supra,
because such a remand would be unnecessary if the district court had
concluded correctly that the prior statement was otherwise inadmissible.
                       UNITED STATES v. BARILE                       11
Branch, 970 F.2d 1368, 1370 (4th Cir. 1992) ("Before admitting evi-
dence for consideration by the jury, the district court must determine
whether its proponent has offered a satisfactory foundation from
which the jury could reasonably find that the evidence is authentic.").

   To the extent that the Government argues that because the prior
statements were made by a third party they are inadmissible on hear-
say grounds, its position is untenable. If Barile can lay a foundation
for the statements, they are admissible over any hearsay objection
because Kroen made them in her capacity as a government official on
matters within the scope of her employment, and as such, the state-
ments are of a party-opponent and therefore not hearsay. See Fed. R.
Evid. 801(d)(2)(D).

                                  III.

   Barile also contends that the district court erred by excluding opin-
ion testimony regarding the materiality of Barile’s allegedly false
statement. Robert Sheridan, a former director of ODE and author of
the guidance document outlining requirements for 510(k) submis-
sions, was prepared to testify that the misleading statements in the
510(k) submission for the Passport with ST were not material. The
district court, however, ruled that Sheridan could not "testify as to
intent of the law, application of the law, and anything that is within
the province of the jury." (J.A. at 617.) The district court stated two
reasons for restricting Sheridan’s testimony. First, the district court
ruled that Barile did not give proper notice under Federal Rule of
Criminal Procedure 16 regarding Sheridan’s opinion that any misrep-
resentations in the 510(k) submissions were not material. Second, the
district court concluded that such testimony would not be helpful to
the jury. We review both reasons below.

                                  A.

   Barile was required under Rule 16(b)(1)(C) to "disclose to the gov-
ernment a written summary of testimony that the defendant intends to
use under Rule 702, 703, or 705 of the Federal Rules of Evidence as
evidence at trial . . . ." Fed. R. Crim. P. 16(b)(1)(C). "This summary
shall describe the witnesses’ opinions, the bases and reasons for those
opinions, and the witnesses’ qualifications." Id. Barile argues that his
12                     UNITED STATES v. BARILE
counsel’s letter of August 16, 2000, disclosed precisely the opinion
testimony Sheridan intended to give: "Mr. Sheridan is expected to tes-
tify about the lack of materiality of alleged misrepresentations in the
510(k)s for the devices in the Indictment." (J.A. at 1061.) The district
court ruled, however, that the August 16, 2000 letter did not give the
government proper notice because it lacked specificity. Because the
summary of Sheridan’s testimony in the letter did not describe Sheri-
dan’s opinions beyond stating the conclusion he had reached and did
not give the reasons for those opinions as required under Rule
16(b)(1)(C), we conclude, as the district court did, that the letter did
not satisfy the rule. Upon finding a violation of Rule 16, the district
court has discretion under the Federal Rules of Criminal Procedure to
determine the proper remedy. See Fed. R. Crim. P. 16(d)(2); United
States v. Muse, 83 F.3d 672, 675 (4th Cir. 1996) ("[A] trial court’s
decision as to the appropriate remedy [for a discovery violation] may
only be reversed for abuse of discretion."). In this case, the trial
court’s remedy was to allow Sheridan to testify on the procedure,
practice, and history of 510(k) submissions but not give his opinion
regarding the materiality of the misrepresentations in the 510(k) sub-
missions. Rule 16(d)(2) specifically allows the district court to "pro-
hibit the party [who does not comply with the discovery rules] from
introducing evidence not disclosed." See Fed. R. Crim. P. 16(d)(2).
Because Barile did not give a proper summary of Sheridan’s opinion
on materiality, failing to give the bases and reasons for his opinions,
the district court’s exclusion of this portion of his testimony is an
acceptable remedy under the rule.

                                  B.

   The district court also limited Sheridan’s testimony on the ground
that an expert’s opinion regarding the materiality of statements on a
particular 510(k) submission would invade the "province of the jury"
and that such opinion testimony would "not assist the jury." (J.A. at
617.) Whether the excluded portion of Sheridan’s testimony is admis-
sible absent the district court’s Rule 16 sanction is an issue that may
arise again should a new trial be required on remand, and we there-
fore address it here.6
  6
   We express no opinion on whether, in a second trial of the same
defendant, a district court may limit the testimony of an expert witness
for a Rule 16 violation in the previous trial.
                       UNITED STATES v. BARILE                        13
   Sheridan was permitted to testify about the procedure, practice, and
history of 510(k) submissions and to respond to hypotheticals. The
district court, however, did not allow him to testify "as to the particu-
lar 510(k) submissions in question and as to whether the submissions
were reasonable or correct or in compliance with the law . . . ." (J.A.
at 617.) He was prepared to testify that "the submissions were not
unreasonable and did not contain materially misleading statements."
(J.A. at 812.) We conclude that the district court’s exclusion of all
opinion testimony regarding the particular 510(k) submissions at issue
was too broad to be justified on the ground that his testimony
addressed an issue exclusively within the province of the finder of
fact.

   Federal Rule of Evidence 704(a) provides that, with certain excep-
tions not relevant here, "testimony in the form of an opinion or infer-
ence otherwise admissible is not objectionable because it embraces an
ultimate issue to be decided by the trier of fact." Rule 704(a) was
designed specifically to abolish the "ultimate issue" rule. Fed. R.
Evid. 704 advisory committee’s notes. The rule, however, "does not
lower the bars so as to admit all opinions." Id. "As a condition to
admissibility under Rule 704(a), testimony on ultimate issues must be
otherwise admissible under the Rules of Evidence." Weinstein’s Fed-
eral Evidence § 704.03[1] (2d ed. 2001). Therefore, although opinion
testimony that embraces an ultimate issue cannot be excluded under
Rule 704(a), it may be excludable on other grounds. See Torres v.
County of Oakland, 758 F.2d 147, 150 (6th Cir. 1985) ("The effect
of Rule 704 is merely to remove the proscription against opinions on
‘ultimate issues’ and to shift the focus to whether the testimony is
‘otherwise admissible.’"). As the advisory committee notes make
clear,

    [u]nder Rule 701 and 702, opinions must be helpful to the
    trier of fact, and Rule 403 provides for exclusion of evi-
    dence which wastes time. These provisions afford ample
    assurances against the admission of opinions which would
    merely tell the jury what result to reach, somewhat in the
    manner of the oath-helpers of an earlier day.

Fed. R. Evid. 704 advisory committee’s notes.
14                      UNITED STATES v. BARILE
    Federal Rule of Evidence 702 provides that "[i]f scientific, techni-
cal, or other specialized knowledge will assist the trier of fact to
understand the evidence or to determine a fact in issue, a witness
qualified as an expert . . . may testify thereto in the form of an opinion
or otherwise." Expert testimony on an ultimate issue is therefore
excludable under Rule 702 if it does not aid the jury. Kopf v. Skyrm,
993 F.2d 374, 377-78 (4th Cir. 1993) (stating that while "[a]n opinion
is not objectionable simply because it embraces an ultimate issue to
be decided by the trier of fact, . . . such an opinion may be excluded
if it is not helpful to the trier of fact under Rule 702") (internal quota-
tion omitted). Expert testimony that merely states a legal conclusion
is less likely to assist the jury in its determination.7 See Woods v.
Lecureux, 110 F.3d 1215, 1220 (6th Cir. 1997) ("It is, therefore,
apparent that testimony offering nothing more than a legal conclusion
—i.e., testimony that does little more than tell the jury what result to
reach—is properly excluded under the Rules."); Weinstein’s Federal
Evidence § 704.04[2][a] (2d ed. 2001) ("The most common reason for
excluding opinion testimony that gives legal conclusion is lack of
helpfulness . . . . The testimony supplies the jury with no information
other than the witness’s view of how the verdict should read."). The
role of the district court, therefore, is to distinguish opinion testimony
that embraces an ultimate issue of fact from opinion testimony that
states a legal conclusion. This task, however, is not an easy one. See
Owen v. Kerr-McGee Corp., 698 F.2d 236, 240 (5th Cir. 1983)
("[S]eparating impermissible questions which call for overbroad or
legal responses from permissible questions is not a facile one.").

   The best way to determine whether opinion testimony contains
legal conclusions, "is to determine whether the terms used by the wit-
ness have a separate, distinct and specialized meaning in the law dif-
ferent from that present in the vernacular." Torres, 758 F.2d at 151;
Lecureux, 110 F.3d at 1220 ("It is also appropriate to exclude ‘ulti-
mate issue’ testimony on the ground that it would not be helpful to
  7
   We note, however, that "in some circumstances, opinion testimony
that arguably states a legal conclusion is helpful to the jury, and thus,
admissible." Weinstein’s Federal Evidence § 704.04[2][a] (2d ed. 2001)
("For example, the testimony may be helpful if the case involves a spe-
cialized industry such as insurance.") (citing Peckham v. Continental
Casualty Ins. Co., 895 F.2d 830, 837 (1st Cir. 1990)).
                       UNITED STATES v. BARILE                        15
the trier of fact when the terms used by the witness have a separate,
distinct and specialized meaning in the law . . . .") (emphasis and cita-
tion omitted). To determine when a question posed to an expert wit-
ness calls for an improper legal conclusion, the district court should
consider first whether the question tracks the language of the legal
principle at issue or of the applicable statute, and second, whether any
terms employed have specialized legal meaning. See Torres, 758 F.2d
at 151 (concluding that "discrimination" has a specialized legal mean-
ing in a Title VII case). In many circumstances, a problematic ques-
tion can be more carefully phrased to elicit similar information yet
avoid a response that constitutes a mere legal conclusion. See id.
(explaining that a question asking whether an expert believed that an
employer "discriminated" against the defendant could be rephrased to
ask whether the expert believed the defendant’s national origin "moti-
vated" certain treatment). An example of a question that should be
excluded is: "Did T have capacity to make a will?" Fed. R. Evid. 704,
advisory committee’s notes. This question, because it is phrased in
broad terms and uses a word with a specialized legal meaning, "could
readily elicit a legal as well as a fact based response." Cf. Owen, 698
F.2d at 240 ("A direct response, whether it be negative or affirmative,
would supply the jury with no information other than the expert’s
view of how its verdict should read."). Some examples, on the other
hand, of questions that need not be excluded are: "Did T have suffi-
cient mental capacity to know the nature and extent of his property?"
or "Did T have sufficient mental capacity to know the natural objects
of his bounty?" or "Did T have sufficient mental capacity to formulate
a rational scheme of distribution?" See Fed. R. Evid. 704, advisory
committee’s notes. The latter questions are more specific, do not
invade the judge’s province of instructing the jury regarding the
meaning of specialized legal terms, and would elicit responses that
give the jury insight into the bases for the expert’s conclusion.

   Sheridan was prepared to testify that "while there was a lack of
clarity in the three 510(k) submissions in question, the submissions
were not unreasonable and did not contain materially misleading
statements." (J.A. at 811.) Sheridan’s conclusion that the 510(k) sub-
missions did not contain "materially misleading statements" arguably
constitutes a legal conclusion because materiality has a specialized
legal meaning, and it is therefore within the district court’s discretion
to exclude such testimony. See United States v. David, 83 F.3d 638,
16                      UNITED STATES v. BARILE
640 n.2 (4th Cir. 1996) (defining materiality as having "a natural ten-
dency to influence agency action or [capability] of influencing agency
action.") (internal quotation omitted). In an attempt to elicit testimony
on the materiality of statements in the 510(k) submissions without
merely stating a legal conclusion, Barile’s counsel attempted to ask
Sheridan whether the submissions were "reasonable." (J.A. at 611.)
Specifically, Sheridan was prepared to testify that "combining actual
test data for the Passport device along with actual test data for the ST
Segment, was unclear but not unreasonable." (J.A. at 811.) Opinion
testimony on whether the data submitted in a 510(k) submission were
reasonable would not merely state a legal conclusion and therefore is
not excludable on the ground that it invades the province of the jury.
Therefore, if the other rules of evidence have been met, including the
requisites of Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S.
579 (1993), and its progeny, an expert opinion on whether various
aspects of the 510(k) submissions on which Barile was indicted were
reasonable is precisely the type of expert testimony that could assist
the trier of fact in its determination.8 Fed. R. Evid. 702 ("If . . . spe-
cialized knowledge will assist the trier of fact to understand the evi-
dence or to determine a fact in issue, a witness qualified as an expert
. . . may testify thereto in the form of an opinion or otherwise.").
Assuming a retrial9 and absent any other basis for exclusion, the dis-
trict court must exercise its discretion in considering the admissibility
of Sheridan’s testimony according to the framework established by
Rules 403, 701, 702, and 704.

                                    IV.

   For the foregoing reasons, we conclude that the district court’s
stated ground for excluding the prior statements that Barile attributes
to Kroen was incorrect and that, if the proper foundation can be laid,
the erroneous exclusion of the statement affected Barile’s substantial
  8
    The district court ruled that Sheridan was qualified as an expert on the
510(k) submission process. We therefore reject the Government’s con-
tention that Sheridan is not qualified to give opinion testimony on ulti-
mate issues of fact. There is no separate category of experts qualified to
give "ultimate issue" opinions. See Garret v. Desa Industries, Inc., 705
F.2d 721, 725 (4th Cir. 1983).
  9
    We express no opinion on whether a new trial is required.
                        UNITED STATES v. BARILE                        17
rights. If the district court determines that the statements are attribut-
able to Kroen, it must grant Barile a new trial on count two. We must
remand, however, to allow the district court to determine whether
Barile can lay the foundation to demonstrate that the prior inconsis-
tent statements are attributable to Kroen. We affirm the district
court’s exclusion of Sheridan’s expert testimony under Federal Rule
of Criminal Procedure 16(d)(2) but, in an analysis that is of potential
relevance on remand, we find that the district court’s limitation on the
scope of his testimony on the ground that his testimony would not be
helpful to the jury was overbroad.

                                 REMANDED WITH INSTRUCTIONS
