United States Court of Appeals
                            FOR THE EIGHTH CIRCUIT
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                                   No. 03-1709
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United States of America,                 *
                                          *
             Appellee,                    *
                                          *      Appeal from the United States
      v.                                  *      District Court for the
                                          *      District of Nebraska.
John E. Davis,                            *
                                          *          [PUBLISHED]
             Appellant.                   *

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                                Submitted: December 17, 2003
                                    Filed: February 2, 2004
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Before WOLLMAN, LAY, and HANSEN, Circuit Judges.
                        ________________

HANSEN, Circuit Judge.

      John E. Davis was charged with conspiracy to distribute 500 grams or more of
methamphetamine, in violation of 21 U.S.C. §§ 841 and 846; tampering with a
witness, in violation of 18 U.S.C. § 1512; and use and discharge of a firearm during
a drug trafficking offense, in violation of 18 U.S.C. § 924(c)(1)(A)(iii). A jury
convicted Davis on all three counts, and the district court1 sentenced him to life in


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        The Honorable Richard G. Kopf, Chief Judge, United States District Court
for the District of Nebraska.
prison. Davis appeals, arguing that the evidence was insufficient to support the
convictions, that the district court abused its discretion in admitting prejudicial
evidence, and that the district court erred in imposing his sentence. We affirm his
convictions and his sentence.

                           I. Sufficiency of the Evidence
      In resolving a challenge to the sufficiency of the evidence supporting a
conviction, we must view the evidence in the light most favorable to the prosecution.
 See Miller v. Lock, 

, 870 (8th Cir. 1997). If "any rational trier of fact
could have found the essential elements of the crime beyond a reasonable doubt," we
must uphold the conviction. 

that the jury's verdict as to the
conspiracy charge was not supported by sufficient evidence because much of the
evidence came from cooperating witnesses. As we have held in similar cases, the
testimony of cooperating witnesses "more than suffices to sustain a conviction for
conspiracy to distribute methamphetamine," United States v. Aguilar-Portillo, 

, 747 (8th Cir. 2003), and any question as to the credibility of the
cooperating witnesses is for the jury alone to determine, United States v. Mangine,

, 823 (8th Cir. 2002). In this case, much of the physical and
documentary evidence presented to the jury corroborated the cooperating witnesses'
testimony. Thus, there was more than sufficient evidence to convict Davis on the
conspiracy charge. Furthermore, even if the evidence suggests that there were
multiple conspiracies – an argument Davis makes for the first time on appeal – Davis
could not have been prejudiced because the evidence was sufficient for the jury to
conclude that Davis was involved in all of the conspiracies. C.f. United States v.
Kamerud, 

, 1013 (8th Cir.), cert. denied, 

(2003).

      Davis also argues that there was insufficient evidence to support the tampering
with a witness charge because there was not a federal investigation pending at the
time he shot Mark Osborn. This argument fails because the statute does not require
proof that a federal case was pending at the time of the alleged tampering, see 18

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U.S.C. § 1512(e)(1), and there is sufficient circumstantial evidence to prove that
Davis acted under a belief that Osborn was a potential witness against him. Finally,
because the physical and circumstantial evidence strongly suggests that Davis shot
Osborn in order to keep him from testifying about Davis's role in the drug conspiracy,
there is also sufficient evidence for the jury to have found that Davis fired a weapon
in furtherance of the conspiracy.

                            II. Admissibility of Evidence
       Davis argues that the district court should not have admitted evidence relating
to Davis's alleged threats and beatings of women, including a young girl, because it
was highly prejudicial, and neither relevant nor probative. We review evidentiary
rulings for abuse of discretion. See United States v. Maynie, 

, 915 (8th
Cir. 2001), cert. denied, 

, and cert. denied, 

(2002). The
prosecution presented evidence that Davis committed acts of violence and made
threats against Joanne Winter, Mark Osborn, and Osborn's children for the purpose
of silencing potential witnesses and furthering the drug conspiracy. We have upheld
the admission of similar evidence in other cases, see, e.g., 

United States
v. Dierling, 

, 730-31 (8th Cir. 1997), cert. denied, 

, and
cert. denied, 

, and cert. denied, 

(1998), including
evidence of threats made to harm a potential witness's children, see United States v.
Montano-Gudino, 

, 505 (8th Cir. 2002). Because drug dealing is often
a violent vocation, and because the evidence of threats and violence was presented
to show the lengths that Davis would go to protect the conspiracy, its probative value
was substantial and far outweighed any prejudicial effect. The district court did not
abuse its discretion in admitting such evidence.

                             III. Sentencing Guidelines
       Davis raises three arguments challenging the district court's determination of
his sentence under the Sentencing Guidelines. First, Davis argues that the district
court erred in imposing a two-level enhancement for obstruction of justice pursuant

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to U.S.S.G. § 3C1.1. We conclude that the district court did not clearly err in finding
that Davis's threats and acts of violence against Mark Osborn, Margie Smith, James
Smith, and Joanne Winter were calculated to impede a criminal investigation and
therefore constituted an obstruction of justice. United States v. Swick, 

,
787 (8th Cir. 2003) (standard of review).

       Second, Davis argues that the district court erred in imposing a four-level
aggravating role enhancement under U.S.S.G. § 3B1.1(a). Because the evidence
shows that Davis directed the activities of at least one other coconspirator, Mary
Negethon, c.f. United States v. Sarabia-Martinez, 

, 451 (8th Cir. 2002),
and exercised control over other coconspirators through threats or violence, c.f.
United States v. Slaughter, 

, 585 (5th Cir. 2000), cert. denied, 

(2001), the district court did not clearly err in concluding that Davis was a
leader or organizer of the conspiracy. We affirm the district court's imposition of the
four-level enhancement.

       Third, Davis argues that the district court erred in relying upon the testimony
of cooperating witnesses to calculate the amount of drugs involved in the conspiracy.
We give great deference to the district court's evaluation of witness credibility and its
calculation of drug quantity. See United States v. Quintana, 

, 702 (8th
Cir. 2003). Because the testimony of the witnesses believed by the court to be
credible is sufficient to support the district court's determination that Davis was
responsible for a minimum of 10 kilograms of methamphetamine, we see no clear
error in the district court's findings, and we affirm its calculation of the base offense
level.

      Accordingly, the judgment of the district court is affirmed.
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