                  United States Court of Appeals
                              For the Eighth Circuit
                          ___________________________

                                  No. 12-1666
                          ___________________________

                              United States of America

                         lllllllllllllllllllll Plaintiff - Appellee

                                            v.

                               Charles Andrew Crocker

                        lllllllllllllllllllll Defendant - Appellant
                                        ____________

                      Appeal from United States District Court
                  for the Eastern District of Arkansas - Little Rock
                                   ____________

                           Submitted: September 17, 2012
                             Filed: September 27, 2012
                                   (Unpublished)
                                   ____________

Before MELLOY, BEAM, and BENTON, Circuit Judges.
                           ____________

PER CURIAM.

      Charles Crocker appeals his 121-month sentence, imposed by the district court1
following the entry of a guilty plea for one count of conspiracy to possess with intent


      1
        The Honorable Brian S. Miller, United States District Judge for the Eastern
District of Arkansas.
to distribute oxycontin and hydrocodone. Crocker's claims on appeal are twofold but
interrelated. He argues that not only was his trial counsel ineffective for failing to
adequately and vigorously cross-examine a government witness, but that the district
court erred in relying upon that particular testimony in calculating the drug quantity
attributed to Crocker for sentencing purposes.

       It is the exceptional circumstance wherein we address Crocker's claims
regarding his counsel's representation in a direct appeal such as this. "This is not an
instance 'where the record has been fully developed, where not to act would amount
to a plain miscarriage of justice, or where counsel's error is readily apparent.'" United
States v. Sanchez-Garcia, 685 F.3d 745, 755 (8th Cir. 2012) (quoting United States
v. Hubbard, 638 F.3d 866, 869 (8th Cir. 2011). We thus decline to address the
ineffective-assistance claim on appeal. A post-conviction proceeding is the
appropriate venue for Crocker's claims.

       As to the court's drug quantity calculation, the plea entered by Crocker in this
case followed an investigation by law enforcement into certain of Crocker's dealings
in 2009 and 2010. At sentencing, the government offered the testimony of five
individuals concerning the quantity of pills involved in the conspiracy to which
Crocker pleaded guilty. Specifically, the government offered the testimony of one
special agent of the Federal Bureau of Investigation involved in the investigation, as
well as four individuals that purchased pills from Crocker. A sentencing court's
calculation of drug quantity is a factual finding that we review for clear error, applying
the preponderance-of-the-evidence standard. United States v. Turner, 603 F.3d 468,
471 (8th Cir.), cert. denied, 131 S. Ct. 820 (2010). This court will overturn a finding
of drug quantity "only if the entire record definitely and firmly convinces us that a
mistake has been made." United States v. Gonzales-Rodriguez, 239 F.3d 948, 953
(8th Cir. 2001) (internal quotation omitted). Additionally, "[a] district court's
assessment of a witness's credibility is almost never clear error given that court's
comparative advantage at evaluating credibility." United States v. Killingsworth, 413

                                           -2-
F.3d 760, 763 (8th Cir. 2005). We see no clear error here. There is nothing in this
record that definitely and firmly convinces us that a mistake has been made.

      We affirm.
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