Defendant James K. Farnham was called before a grand jury apparently investigating possible tax violations by his employer, Joseph Griggs Associates, an architectural and engineering firm, together with several other businesses. The investigating case agents interviewed Farnham prior to his testimony, and the grand jury questioned Farnham about his involvement in the preparation and submission to the Department of Housing and Urban Development (HUD) of plans for an apartment project, which were allegedly falsified in order to secure HUD’s approval. Farnham admitted to having prepared two sets of plans but denied that either was false.
Subsequently, Farnham was indicted for making false declarations to a grand jury *333 in violation of 18 U.S.C. § 1623. 1 At trial, the government introduced Famham’s grand jury testimony, together with the trial testimony of others, including the two case agents, tending to show that Farnham lied to the grand jury. Farnham was convicted of three counts of violating 18 U.S.C. § 1623 and received a consolidated sentence of three years, the service of all but six months of which was suspended.
Farnham’s appeal rests on two grounds. First, he contends that the government failed to establish the materiality of any false statements because it failed to prove the scope of the grand jury investigation. Second, he asserts that the district court’s refusal to sequester the second case agent during the testimony of the first case agent denied him a fair trial.
I.
In order to convict an accused under 18 U.S.C. § 1623 for perjury before a grand jury, the government must show that the false declarations supporting the perjury prosecution were material to the grand jury’s investigation. 18 U.S.C. § 1623. A statement is material for purposes of § 1623 if it has “the natural effect or tendency to impede, influence or dissuade the grand jury from pursuing its investigation.”
United States v. Paolicelli,
Here, the government sought to establish the scope of the grand jury’s investigation by introducing 37 of the 43 pages of Farnham’s testimony before the grand jury and by the testimony of the two case agents assisting the grand jury investigation. Although this may not have been the most reliable method of establishing the nature of the investigation, we conclude that it was sufficient to permit the district court to determine whether the false statements were material.
The government bears the burden of establishing materiality by showing a nexus between the false statements and the scope of the grand jury’s investigation.
See, e.g., McComb,
*334
While the government must establish a nexus between the investigation and the false declaration, it need not prove the connection beyond a reasonable doubt.
See, e.g., Berardi,
II. •
Federal Rule of Evidence 615 requires the trial court, at the request of a party, to sequester a witness, expressly providing an exception for “an officer or employee of a party which is not a natural person designated as its representative by its attorney.”
4
Under this exception, the district court may allow the government’s chief investigating agent to remain in the courtroom throughout the proceedings, even if he is expected to testify.
United States v. Parodi,
We begin our consideration of this problem by noting that the application of Rule 615(2) under these circumstances presents us with an issue of first impression and that we proceed largely without the guidance of other federal courts. The little authority that exists is unclear, conclusory and conflicting.
Ignoring the mandatory (“shall”) language of the rule, the Fifth Circuit invoked an abuse of discretion standard to uphold a trial court’s refusal to exclude one of two Drug Enforcement Administration case agents from the proceedings, even though the agent in question did not testify until the end of the trial.
United States v. Alvarado,
On the other hand, both the Fifth Circuit and the United States District Court for the District of Delaware have suggested in dicta that 615(2) clearly contemplates exempting only a single representative from a sequestration request.
Causey,
Relying on the mandatory language of Rule 615 and the singular phrasing of the exception embodied in 615(2), we hold that the district court erred in refusing to sequester Agent Martin, if not during the entire trial, at least during the testimony of his colleague. As the Advisory Committee noted, the sequestration of witnesses effectively discourages and exposes fabrication, inaccuracy, and collusion. Notes of Advisory Committee on Proposed Rules. Scrupulous adherence to this rule is particularly necessary in those cases in which the outcome depends on the relative credibility of the parties’ witnesses.
We reject the government’s suggestion that the technical violation of Rule 615 lacks consequence because the defendant cannot prove prejudice. Instead, we understand the mandatory, unambiguous language of the rule to reflect the drafters’ recognition that any defendant in Farnham’s position would find it almost impossible to sustain the burden of proving the negative inference that the second agent’s testimony Would have been different had he been sequestered. A strict prejudice requirement of this sort would be not only unduly harsh but also self-defeating, in that it would swallow a rule carefully designed to aid the truth-seeking process and preserve the durability and acceptability of verdicts. Rule 615 thus reflects an a priori judgment in favor of sequestration, and the exceptions should be construed narrowly in favor of the party requesting sequestration.
Believing that Rule 615 should be applied strictly, we reverse the conviction as to Count Three and remand for resentencing as to Counts One and Two. Although Rule 615 does not require that Farnham show prejudice, we remain bound by the harmless error rule. The agents’ testimony related only to Count Three, and any possible collusion or tailoring, however egregious, could not have affected the out *336 come as to the other two counts. This is the exceptional case because the facts are such that any presumption of prejudice is rebutted. Because Farnham received a consolidated sentence, we are, however, unable to determine what effect, if any, his conviction under Count Three had on the sentence imposed on him and thus to allocate his punishment. We therefore return the case to the district court for resentenc-ing on Counts One and Two, and if the government be so advised, Farnham may be retried on Count Three.
REVERSED AND REMANDED.
Notes
. 18 U.S.C. § 1623 provides in relevant part:
(a) Whoever under oath (or in any declaration, certificate, verification, or statement under penalty of perjury as permitted under section 1746 of title 28, United States Code) in any proceeding before or ancillary to any court or grand jury of the United States knowingly makes any false material declaration or makes or uses any other information, including any book, paper, document, record, recording, or other material, knowing the same to contain any false material declaration, shall be fined not more than $10,000 or imprisoned not more than five years, or both.
. As defendant points out, the Fifth Circuit has held that the testimony of a case agent as to his own work in aid of a grand jury investigation cannot alone establish the scope of that investigation.
United States v. Cosby,
. In
Bailey,
we cited with approval
United States v. Ostertag,
.Rule 615 of the Federal Rules of Evidence provides:
At the request of a party the court shall order witnesses excluded so that they cannot hear the testimony of other witnesses, and it may make the order of its own motion. This rule does not authorize exclusion of (1) a party who is a natural person, or (2) an officer or employee of a party which is not a natural person designated as its representative by its attorney, or (3) a person whose presence is shown by a party to be essential to the presentation of his cause.
. The government has not urged, nor do we suggest, that the second agent might have qualified under Rule 615(3). In fact, this perjury prosecution was disposed of in a relatively simple, two-day trial, and the constant attendance of two government agents who were present to testify to the same conversation cannot be deemed essential.
