United States Court of Appeals
                            FOR THE EIGHTH CIRCUIT
                                   ___________

                                   No. 05-1718
                                   ___________

United States of America,               *
                                        *
              Appellee,                 *
                                        * Appeal from the United States
         v.                             * District Court for the
                                        * Southern District of Iowa.
Aaron Lynn Selby,                       *
                                        *      [UNPUBLISHED]
              Appellant.                *
                                   ___________

                             Submitted: June 16, 2006
                                Filed: June 19, 2006
                                 ___________

Before RILEY, MAGILL, and GRUENDER, Circuit Judges.
                            ___________

PER CURIAM.

       Aaron Lynn Selby (Selby) challenges the sentence imposed by the district
     1
court after he pled guilty to conspiring to distribute methamphetamine, in violation
of 21 U.S.C §§ 846 and 841(b)(1)(A), and conspiring to distribute marijuana, in
violation of 21 U.S.C. §§ 846 and 841(b)(1)(D). Selby was subject to a mandatory
minimum sentence of life imprisonment. Prior to sentencing, however, the
government filed a substantial-assistance downward-departure motion under 18
U.S.C. § 3553(e) and U.S.S.G. § 5K1.1 and recommended a 20% sentence reduction

         1
        The Honorable James E. Gritzner, United States District Judge for the Southern
District of Iowa.
of 405 months. Selby, on the other hand, requested that the court consider 360 months
as the starting point for his substantial-assistance reduction. The court ultimately
sentenced Selby to 263 months’ imprisonment, which represented a 35% reduction
from 405 months.

      On appeal, Selby contends that the district court erred in “arbitrarily” choosing
405 months as the starting point from which to apply the substantial-assistance
departure and that “life” is more appropriately defined in this context as 360 months.
For support, Selby relies upon 18 U.S.C. § 3582(c)(1)(A)(ii), and United States v.
Prevatte, 

(7th Cir. 1995). Selby maintains that, if the court had properly
defined life as 360 months, a 35% reduction would have resulted in a 234-month
sentence.

       We review de novo the district court’s interpretation and application of the
Guidelines. See United States v. Mashek, 

, 1017 (8th Cir. 2005).
“When construing the Guidelines, we look first to the plain language, and where that
is unambiguous we need look no further.” United States v. Bah, 

, 427
(8th Cir. 2006) (quotation omitted). Where the plain language of the Sentencing
Guidelines is ambiguous, we will interpret the Guidelines in the manner that most
clearly adheres to the Sentencing Commission’s intent. See, e.g., United States v.
Gomez-Hernandez, 

, 978-79 (8th Cir. 2002). The best source of the
Sentencing Commission’s intent is the Sentencing Guidelines Manual itself. See
United States v. Laughrin, 

, 1249 (10th Cir. 2006). The Sentencing
Guidelines Manual does not specifically set forth, for a life sentence, a fixed
equivalent in terms of months. It is clear, however, that the Sentencing Commission’s
intent was not to define a life sentence as 360 months, because under the Sentencing
Table, there are two separate sentencing levels where the range goes up to 405 months
before reaching life. See generally U.S.S.G. Ch. 5, Pt. A (Sentencing Table). In other
words, Selby supports an interpretation that would render a sentence of 360 months
(Selby’s presumptive life sentence under the Guidelines) appropriate for crimes more

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serious than those warranting a sentence of 405 months. This clearly was not the
Sentencing Commission’s intent. Additionally, it appears Selby actually received a
favorable starting point of 405 months. See 2004 Sourcebook of Federal Sentencing
Statistics, United States Sentencing Commission, Appendix A (“Prior to fiscal year
1993, the Commission defined life sentences as 360 months. However, to reflect life
expectancy of federal criminal defendants more precisely and to provide more
accurate length of imprisonment information, life sentences are now defined as 470
months.”); see also United States v. Keller, 

, 711 (8th Cir.) (rejecting
argument that district court erroneously calculated substantial-assistance reduction on
life sentence; holding that court used correct starting point of 470 months), cert.
denied, 

(2005). Accordingly, we hold Selby has failed to demonstrate
the district court erred in using 405 months as the starting point for applying the
substantial-assistance departure.

       We further hold that Selby’s reliance on section 3582(c)(1)(A)(ii) is misplaced
because that provision does not set the definitive standard as to what is meant by a life
sentence under the statutory sentencing framework. Rather, it applies to the
discretionary modification of a sentence for a defendant who is at least 70 years old,
has served at least 30 years in prison, and is no longer considered dangerous. Selby’s
reliance on Prevatte likewise is misplaced because Prevatte does not involve the
application of a mandatory minimum sentence of life. See 

(holding 636-month sentence was abuse of discretion in light of Seventh Circuit’s
prior holding that where legislatively enacted sentencing scheme has expressly
deprived court of possibility of imposing life sentence, sentence for term of years
exceeding defendant’s approximate life expectancy would ordinarily constitute abuse
of discretion (quotation omitted)).

      For the foregoing reasons, we affirm.
                      ______________________________



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