Appellants were tried and convicted by a jury on charges stemming from a fifteen-count indictment handed down by a grand jury. Appellants raise numerous issues on appeal, including insufficiency of the evidence, erroneous evidentiary rulings, and improper sentencing. We find these contentions to be without merit and AFFIRM the convictions of each appellant on all counts.
I. BACKGROUND
A grand jury returned a fifteen-count indictment against James Willis Saget, Julius Phillip Hall, Herbert Nathaniel Johnson, Lamar Roberson and two other defendants who are not a party to this appeal. All four appellants were charged with conspiring to possess with intent to distribute cocaine base (“crack”) (count 1). Hall and Johnson were charged with two counts each of travelling in interstate commerce with intent to facilitate the distribution of crack (counts 4 & 5), and with obstruction of justice (count 10). Hall, Johnson and Saget were charged with laundering the proceeds of illegal drug transactions (count 15). Johnson and Roberson were charged with multiple counts of distribution of crack. (Johnson — counts 6, 7, 8, 9,11 & 13; Roberson — counts 11 & 12). Finally, Hall was charged with perjury before the grand jury (count 14). With the exception of the money laundering counts against Saget and Johnson, the appellants were found guilty on all counts. The district court *707 sentenced Hall, Johnson and Roberson to life imprisonment for the conspiracy and to at least one concurrent term of twenty years or more for the other counts on which they were convicted. Saget was sentenced to imprisonment for 330 months, to be followed by 5 years supervised release.
The grand jury indictment resulted from the investigation of a cocaine conspiracy involving the appellants. The conspiracy was set up in the form of a partnership, with preassigned ownership interests, for the purpose of obtaining quantities of crack cocaine from southern Florida and transporting them to Savannah, Georgia for further distribution. Hall was the planner and head of the partnership. Saget was responsible for transporting the cocaine from Florida to Savannah where other members of the conspiracy would divide the quantity into smaller parcels and further distribute the cocaine. Saget delivered one-half of a kilogram of cocaine at least twice a month for ten months. Johnson and Roberson were primarily responsible for selling the smaller quantities of crack. Hall and Johnson each contributed money for the initial shipment of cocaine. Thereafter, over the course of their operation, Hall wired money to Saget in Florida for drug purchases, and he traveled with Johnson to Florida to deliver money to Sa-get.
After a jury trial resulted in convictions for each appellant, appellants filed post-trial motions for arrest of judgment and for a new trial, which the district court denied. Appellants then filed the instant appeal.
II. DISCUSSION A. MOTION FOR SEVERANCE
Roberson contends that the district court abused its discretion in denying his motion for severance due to the prejudice he suffered by association with the other defendants at trial. Pursuant to Fed. R.Crim.P. 8(b), joinder of multiple defendants is proper whenever there is a “common thread” between the actions charged against them.
United States v. McLain,
B. MOTION FOR MISTRIAL
Roberson challenges the district court’s denial of his motion for mistrial after a government witness’ testimony relating to Johnson’s withdrawn plea agreement. “The decision to grant a mistrial is within the discretion of the trial judge since he is in the best position to evaluate the
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prejudicial effect of a statement or evidence on the jury.”
U.S. v. Blakey,
C. MOTION FOR CONTINUANCE
Roberson contends that the district court abused its discretion in denying his motion for a continuance because the government supplied new evidence two weeks before trial was to begin. Denial of a continuance, requested by a defendant in order to permit additional preparation for trial, must be upheld unless the defendant can show an abuse of discretion and specific, substantial prejudice.
United States v. Gossett,
D. BATSON v. KENTUCKY CHALLENGE
Hall contends that the district court’s acceptance of the government’s explanation for its use of preemptory challenges is clearly erroneous. The government used four of its six preemptory challenges to strike African-American persons from the venire. The district court found that Hall had established a prima facie case of discrimination under the principles set forth in
Batson v. Kentucky,
E. PROSECUTOR’S OPENING STATEMENT '
Roberson contends that he was prejudiced by the government’s opening statement when the prosecutor collectively referred to Johnson and Roberson in describing evidence of cocaine sales. Since Roberson did not object to the prosecutor’s statement at the time it was made or in his motion for a new trial, the allegation of error must be reviewed under a “plain error” standard.
United States v. Young,
Five of those recordings were made by a paid police informant by the name of Tammy Johnson. She makes recorded buys, that is audio recordings, from Herbert Nathaniel Johnson.
And you will hear (Nathaniel) Johnson ... and Lamar Roberson negotiating the sale of crack cocaine to [a third person], ...
On two occasion, you will hear Lamar Roberson attempt to sell crack cocaine to informants who have come with instructions to purchase crack cocaine from Herbert Nathaniel Johnson. (R7-114-115).
The prosecutor was reasonably specific in delineating which evidence was attributable to each defendant. In addition, the prosecutor’s remarks are consistent with the evidence produced at trial. Taken in context and viewed against the opening statement in its entirety, the remarks were not such as to unfairly prejudice Roberson or result in a miscarriage of justice.
F. EVIDENTIARY RULINGS
A district court’s evidentiary ruling must stand unless there appears a clear abuse of discretion.
United States v. Lankford,
1. Admission of Firearm Evidence
Roberson argues that the district court should have excluded evidence of four weapons seized from his house at the time of his arrest because the prejudicial effect of that evidence outweighed its probative value. However, this court has held that possession of weapons is circumstantial evidence of a defendant’s involvement in a cocaine conspiracy because such weapons are often “tools of illegal narcotics trafficking.”
United States v. Terza-do-Madruga,
2. Testimony of an Atheist
Hall moved to strike the testimony of William Earl McDonald, a government *710 witness, arguing that he was incompetent to testify because he swore an oath to God despite the fact that he is an atheist. It is well settled that an oath to God is no longer required in order to testify and that a witness may affirm rather than swear an oath. See 1 U.S.C. § 1 (1985). Fed.R.Evid. 603 requires only that a witness “declare that the witness will testify truthfully, by oath or affirmation administered in a form calculated to awaken the witness’ conscience and impress the witness’ mind with the duty to do so.” Hall asserts that McDonald swore an oath because “that was what was required to be said” and therefore the oath did not impress upon McDonald the duty to tell the truth. In response to questions about his religious beliefs, McDonald testified that he took the oath seriously, that he respected the oath, and that “to the best of my ability, I’m telling the truth.” McDonald was not offered a chance to affirm rather than swear an oath, but the record reflects that he was cognizant of his solemn duty to tell the truth. This comports with the liberal requirements of Rule 603 and the district court correctly denied the motion to strike McDonald’s testimony.
3. Limitations on Hall’s Right to Cross-Examination
Hall contends that the district court impermissibly restricted his cross-examination of McDonald in violation of the 6th amendment.
3
At trial, Hall attempted to impeach the testimony of McDonald with prior inconsistent statements that McDonald had made to FBI agents. Hall’s attorney, reading directly from the agent’s summary, asked if the statement reflected what McDonald had told the agent.
4
In effect, Hall’s attorney was introducing extrinsic evidence to the jury of McDonald’s prior inconsistent statement via the FBI agent’s summary. “Extrinsic evidence of a prior inconsistent statement by a witness is not admissible unless the witness is afforded an opportunity to explain or deny the same_” Fed.R.Evid. 613(b). The district court sustained an objection to Hall’s use of a' summary prepared by an FBI agent without a showing that McDonald had adopted the statements as his own. The district court’s determination whether evidence is supported by a proper foundation is reviewable for an abuse of discretion.
United States v. Miller,
4. Limitations of Hall’s Direct Examination
Hall contends that the district court erroneously placed restrictions on his own testimony and on his direct examination of defense witnesses, which prevented him from showing the extent of income he earned from legitimate businesses as well as the methods he used to win money at gambling. Even relevant evidence “may be excluded if its probative value is substantially outweighed by ... considerations of undue delay, waste of time, or needless presentation of cumulative evidence.” Fed.R.Evid. 403. The district court allowed Hall to answer questions about four legitimate business enterprises and other sources of outside income but sustained an objection as to the relevance of why one of those businesses did not generate income. The fact that a business lost money is certainly irrelevant in trying to prove the extent of legitimate income. In addition, the district court permitted Hall to answer many questions about his gambling activities, including a brief explanation of the methods he used to win money. The district did not allow detailed explanations about the intricacies of Hall’s betting system because of considerations of undue delay and irrelevance. Hall was able to make an adequate showing to the jury that he had income from sources other than cocaine sales, including gambling. The district court did not abuse its discretion in restricting certain lines of questioning, nor was Hall prejudiced in his ability to present his ease to the jury.
5. Admission of Grand Jury Transcript
Hall asserts error by the district court in allowing the jury to review the transcript of the grand jury testimony during its deliberations. Hall’s argument rests on the false premise that the grand jury testimony was not entered into evidence during the trial. The record clearly reflects that the transcript was entered into evidence contemporaneously with two other exhibits. (R9 — 662). Defense counsel objected to the two other exhibits but not to the grand jury transcript. Since Hall was charged with making false declarations before the grand jury, the transcripts of the grand jury proceedings were directly relevant to the government’s case. Where transcripts of grand jury testimony are offered to support a charge of penury, the transcripts constitute substantive evidence of the charge and may be reviewed by the jury during its deliberations. The district court properly allowed the transcript to be considered by the jury during deliberations.
6.Admission of Evidence of a Shooting
Johnson contends that the district court erred in denying his motion for mistrial after a government witness testified that his mother had been shot after the witness had entered a plea agreement. This issue was not raised in Johnson’s motion for new trial and therefore is reviewed for plain error.
Young, supra.
Immediately after the shooting was mentioned, the district court instructed the jury to disregard any statement about the witness’ mother being shot. We must presume that the jury followed that instruction,
United States v. LaSpesa,
G. SUFFICIENCY OF THE EVIDENCE
When a jury finds a defendant guilty, its verdict must stand if
“any
rational trier of fact could have found the essential elements of the crime beyond a reasonable doubt.”'
Jackson, v. Virginia,
1.Count One — Conspiracy to Distribute Cocaine
Each appellant challenges his conviction for conspiracy to distribute cocaine. To convict a defendant of conspiracy under 21 U.S.C. § 846 (Supp.1993), the government must prove “(1) an agreement to possess with intent to distribute cocaine, (2) the defendant’s knowledge of the essential objective of the agreement, and (3) the defendant’s voluntary participation in the illegal venture.”
United States v. Gardiner,
2. Counts J & 5 — The Travel Act
Hall challenges the sufficiency of the evidence with respect to his conviction for violating 18 U.S.C. § 1952 (Supp. 1993), commonly known as the Travel Act. This statute prohibits interstate travel with the intent to “promote, manage, establish, carry on, or facilitate [any] unlawful activity....” 18 U.S.C. § 1952(a)(3). “Unlawful activity” is further defined as “any business enterprise involving ... narcotics or controlled substances.” 18 U.S.C. § 1952(b)(1). If the defendant engages in a continuous course of cocaine distribution rather than a sporadic or casual course of conduct, then the statutory requirement of a business enterprise involving narcotics is satisfied, and a single incident of interstate travel to carry on or facilitate that enterprise violates this statute.
United States v. Smith,
3. Count Fifteen — Money Laundering
Hall also challenges the sufficiency of the evidence with respect to his conviction for money laundering under 18 U.S.C. § 1956(a)(1)(B)(i) (Supp.1993). To establish
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a violation of § 1956(a)(1), the government must prove that the defendant “knowingly conducted a financial transaction which involved the proceeds of drug distribution and that he did so either with the intent to promote his drug business or with knowledge that the transaction was designed to disguise the nature or source of those proceeds.”
United States v. Blackman,
4. Count Ten — Obstruction of Justice
Hall and Johnson were convicted under the omnibus clause of 18 U.S.C. § 1503 (1984) for endeavoring “to influence, obstruct, or impede the due administration of justice” by questioning a grand juror about an investigation. Fed.R.Crim.P. 6(e)(2), which imposes a general rule of secrecy, states that a “grand juror .. shall not disclose matters occurring before the grand jury.” In order to convict an individual under § 1503, the government must prove that the defendants “knowingly and intentionally undertook an action from which an obstruction of justice was a reasonably foreseeable result.”
United States v. Thomas,
H. HALL’S SENTENCE
Hall contends that his sentence is based on an incorrect calculation of the amount of cocaine involved. “The determination of the quantity of cocaine involved in a conspiracy for the purposes of sentencing is a factual determination subject to the clearly erroneous standard.”
United States v. Alston,
I. SENTENCE ENHANCEMENT FOR POSSESSION OF COCAINE BASE (CRACK)
Johnson contends that the term “cocaine base” as used in 21 U.S.C. § 841 (Supp.1993) and in U.S.S.G. § 2D1.1, is unconstitutionally vague. Johnson’s argument is foreclosed by our decision in
United States v. Williams,
J. SENTENCE ENHANCEMENT FOR POSSESSION OF A DANGEROUS WEAPON
The district court, applying U.S.S.G. § 2D 1.1(b)(1)
7
, enhanced Johnson’s base offense level by two points for possession of a dangerous weapon. Johnson argues that his sentence enhancement was improper because there was no showing that he actually possessed or used any weapons. However, a co-conspirator’s sentence may be enhanced for possession of a dangerous weapon if “(1) the possessor is charged as a conspirator, (2) the defendant who’s sentence is to be enhanced was a member of the conspiracy at the time of the firearm possession; and (3) the possession of the firearm was in furtherance of the conspiracy.”
U.S. v. Martinez,
K.REDUCTION OF SENTENCE FOR ACCEPTANCE OF RESPONSIBILITY
Johnson asserts that he should have been granted a two point reduction for acceptance of responsibility because he admitted “his limited involvement” in the charges. In order to qualify for acceptance of responsibility, the sentencing guidelines specify that Johnson must “truthfully [admit] the conduct comprising the offense(s) of conviction, and truthfully [admit] or not falsely [deny] any additional relevant conduct” for which he is accountable. U.S.S.G. § 3E1.1 application note 1(a). “A defendant who falsely denies or frivolously contests relevant conduct that the court determines to be true has acted in a manner inconsistent with acceptance of responsibility.” Id. Johnson has never admitted to being part of the conspiracy, despite the jury’s verdict. Johnson’s denial of his involvement in the conspiracy justi *715 fies the district court’s denial of credit for acceptance of responsibility.
III. CONCLUSION
We have carefully considered all additional issues raised by the appellants on appeal but not specifically addressed above and we find no reversible error as to any appellant. For the foregoing reasons, the convictions of each appellant on each count are AFFIRMED.
Notes
. Cecilia Hall Strobert was indicted on the conspiracy count and tried with the appellants but was acquitted by the jury.
. The FBI agent testified as follows:
Q: Do you recall telling Mr. Johnson that he needed to cooperate in order to help himself?
A: Mr. Spiva, at that point Mr. Johnson had already entered into a plea agreement with the government.
.Hall’s claims of constitutional violations do not change the proper standard of review. The Confrontation Clause of the 6th Amendment “guarantees only an
opportunity
for effective cross-examination, not cross-examination that is effective in whatever way, and to whatever extent the defense might wish."
Kentucky v. Stincer,
. Q: Look down at the bottom where it says, "Cl 73-14 told Hall to have Smith deliver the crack to Montgomery and Hall Street,” This is what you told the government agent that Hall said to you; true? (R8 — 246).
. U.S.S.G. § 2D1.1(c)(2) specifies a base offense level of 40 if the defendant is in possession of "at least 5 KG but less than 15 KG of cocaine base.”
. § 2D1.1(b)(1) provides: "If a dangerous weapon (including a firearm) was possessed, increase by 2 levels."
Application note 3 states: “This adjustment should be applied if the weapon was present, unless it is clearly improbable that the weapon was connected with the offense.”
