                         UNPUBLISHED

UNITED STATES COURT OF APPEALS
                FOR THE FOURTH CIRCUIT


UNITED STATES OF AMERICA,              
                 Plaintiff-Appellee,
                 v.
                                                No. 02-4300
GARRETT JEROME WILLIAMS, a/k/a
J-1,
              Defendant-Appellant.
                                       
            Appeal from the United States District Court
     for the Southern District of West Virginia, at Charleston.
             Charles H. Haden II, Chief District Judge.
                            (CR-01-238)

                  Submitted: September 27, 2002

                      Decided: October 7, 2002

      Before MICHAEL and GREGORY, Circuit Judges, and
               HAMILTON, Senior Circuit Judge.



Affirmed in part and dismissed in part by unpublished per curiam
opinion.


                            COUNSEL

John R. McGhee, Jr., KAY CASTO & CHANEY, P.L.L.C., Charles-
ton, West Virginia, for Appellant. Kasey Warner, United States Attor-
ney, Samuel D. Marsh, Assistant United States Attorney, Charleston,
West Virginia, for Appellee.
2                     UNITED STATES v. WILLIAMS
Unpublished opinions are not binding precedent in this circuit. See
Local Rule 36(c).


                               OPINION

PER CURIAM:

   Garrett Jerome Williams pled guilty to distribution of cocaine base
(crack) in violation of 21 U.S.C. § 841(a) (2000), and was sentenced
to a term of 121 months imprisonment. He appeals his sentence, con-
tending that the district court abused its discretion in refusing to
depart under U.S. Sentencing Guidelines Manual § 5K1.1, p.s. (2001),
for substantial assistance provided by his brother, and under USSG
§ 5K2.0, p.s., on the ground that most of the crack included in Wil-
liams’ relevant conduct was derived from information he provided
voluntarily. He also argues that the district court clearly erred in find-
ing the testimony of a confidential informant credible as to drug
amounts and Williams’ possession of a firearm. See USSG
§ 2D1.1(b)(1). We affirm in part and dismiss in part.

   The sentencing court may not consider a downward departure for
substantial assistance without a government motion for a departure.
United States v. Butler, 272 F.3d 683, 687 (4th Cir. 2001). Moreover,
when the government has not obligated itself to move for a substantial
assistance departure in the event the defendant provides substantial
assistance, the court has no authority to review the government’s
decision not to file a departure motion unless the defendant makes a
strong showing that the government decision was based on an uncon-
stitutional motive or was not rationally related to a legitimate govern-
ment end. Id. Williams’ plea agreement did not obligate the
government to move for a substantial assistance departure and he
made no showing that would have permitted the court to inquire into
the government’s decision. Therefore, assuming we have jurisdiction
to review the issue, we conclude that the district court did not abuse
its discretion in declining to depart.

   The district court’s decision not to depart for other factors, such as
the effect of Williams’ voluntary disclosures on his guideline range,
                      UNITED STATES v. WILLIAMS                       3
is not reviewable on appeal unless the decision is based on a mistaken
perception that the court lacks the legal authority to depart. United
States v. Hall, 977 F.2d 861, 863 (4th Cir. 1992). Williams does not
allege and the record does not reveal that the district court mistakenly
believed it lacked authority to depart. This issue is thus not review-
able on appeal.

   Factual determinations relevant to sentencing are reviewed for
clear error. United States v. Love, 134 F.3d 595, 606 (4th Cir. 1998).
Findings based on the credibility of witnesses are given even greater
deference. United States v. Hassanzadeh, 271 F.3d 574, 580 (4th Cir.
2001).

   The district court found the confidential informant’s testimony at
the sentencing hearing credible because she admitted her own crimi-
nal conduct candidly and the information she provided was supported
to some degree by the testimony of the detective in charge and by that
of Williams’ girlfriend. Given that the district court found her testi-
mony credible, the district court did not clearly err in finding that
Williams was responsible for more than 50 grams of crack and that
an enhancement for possession of a weapon was warranted.

   We therefore affirm the sentence imposed by the district court. We
dismiss that portion of the appeal which contests the district court’s
decision not to depart. We dispense with oral argument because the
facts and legal contentions are adequately presented in the materials
before the court and argument would not aid the decisional process.

                       AFFIRMED IN PART; DISMISSED IN PART
