The Honorable Ronald Lee Gilman, Senior Circuit Judge for the U.S. *

Court of Appeals for the Sixth Circuit, sitting by designation.

FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,

Plaintiff-Appellee,

v.

BILLY MIRANDA FLORES,

Defendant-Appellant.

No. 12-30078

D.C. No.

3:09-cr-05810-

RBL-1

OPINION

Appeal from the United States District Court

for the Western District of Washington

Ronald B. Leighton, District Judge, Presiding

Argued and Submitted

June 7, 2013—Seattle, Washington

Filed August 2, 2013

Before: Arthur L. Alarcón, Ronald Lee Gilman,*

and Sandra S. Ikuta, Circuit Judges.

Opinion by Judge Alarcón
2 UNITED STATES V. FLORES

 This summary constitutes no part of the opinion of the court. It has

**

been prepared by court staff for the convenience of the reader.

SUMMARY

**

Criminal Law

Vacating a sentence and remanding for resentencing, the

panel held that any error in estimating the quantity of drugs

attributable to a conspiracy to distribute oxycodone was

harmless, but that the district court erred in imposing without

an adequate factual basis an enhancement under U.S.S.G.

§ 3B1.4 for use of a person less than eighteen years of age.

COUNSEL

Jonathan I. Edelstein, Law Office of Alan Ellis, New York,

New York, for Defendant-Appellant.

Teal Luthy Miller, Assistant United States Attorney (argued),

and Jenny A. Durkan, United States Attorney, Office of the

United States Attorney, Seattle, Washington, for PlaintiffAppellee.

OPINION

ALARCÓN, Circuit Judge:

Billy Miranda Flores (“Flores”) was convicted on one

count of conspiracy to distribute oxycodone, three counts of
UNITED STATES V. FLORES 3

 Flores also contends that the district court erred in imposing a 1

substantively unreasonable sentence. Given our holding, we do not

address the substantive reasonableness of the sentence. See United States

v. Kilby, 443 F.3d 1135, 1140 (9th Cir. 2006) (holding that if a reviewing

court finds a material error in the Guidelines calculation, it “will remand

for resentencing, without reaching the question of whether the sentence as

a whole is reasonable”).

distribution of oxycodone, one count of possession with

intent to distribute methadone, and one count of possession of

a firearm in furtherance of the methadone charge. The

district court sentenced Flores to 240 months imprisonment—

180 months for the drug charges and 60 months for the

firearm charge, imposed consecutively. Flores appeals his

conviction of the gun charge and his sentence. We have

jurisdiction under 28 U.S.C. § 1291 and 18 U.S.C. § 3742(a).

In this opinion, we consider only Flores’s challenges to his

sentence. In a concurrently filed memorandum disposition,

we address Flores’s separate challenges to his conviction.

See United States v. Flores, __Fed. App’x __ (9th Cir. 2013).

Flores argues that in imposing the sentence, the district

court erred in estimating the quantity of drugs attributable to

the conspiracy under the United States Sentencing

Guidelines, and in applying a two-level sentencing

enhancement under United States Sentencing Guidelines

Manual § 3B1.4 for use of a person less than eighteen years

of age in the conspiracy to distribute oxycodone. We 1

conclude that any error in estimating the quantity of drugs

attributable to the conspiracy was harmless, but that the

district court erred in imposing the sentencing enhancement

without an adequate factual basis. We accordingly vacate

Flores’s sentence and remand for resentencing.
4 UNITED STATES V. FLORES

 At trial, the attorneys and witnesses (and consequently the presentence

2

report, transcripts, parties’ papers, and orders) used the terms

“oxycodone” and “OxyContin” interchangeably. “Oxycodone” is a

generic opioid pain reliever found in a number of prescription medications

and is the sole active ingredient in OxyContin, a widely used prescription

narcotic manufactured by Purdue Pharma L.P. See U.S. Gov’t

Accountability Office, GAO-04-110, Prescription Drugs: OxyContin

Abuse and Diversion Efforts to Address the Problem 1–2, 8–9, 11 (2003).

Oxycodone is classified as a Schedule II controlled substance “because it

has high potential for abuse and may lead to severe psychological or

physical dependence.” Id. at 2 & n.6. We use the terms “oxycodone” and

“OxyContin” interchangeably in our opinion to reflect their usage in the

record.

 The record is unclear as to the start date of the two separate 3

investigations that eventually merged into the joint investigation. DEA

Investigator Errin Jewell testified that he was informed of an ongoing

DEA investigation in June 2008. He learned that the investigation “had

potential to be very complex, a bigger investigation involving the Indian

Smoke Shop . . . and [he] was assigned as the lead investigator on the

investigation.” FBI Special Agent Donald Treat testified that the FBI’s

South Sound Gang Task Force was conducting an investigation before it

joined with the DEA’s Tacoma Narcotics Enforcement Team task force

around early to mid-2008.

I

This case arises out of a joint Federal Bureau of

Investigation (“FBI”) and Drug Enforcement Agency

(“DEA”) investigation into oxycodone and methadone 2

trafficking on Puyallup tribal land in Washington State.

Sometime before the summer of 2008, law enforcement 3

began investigating Flores and the smoke shop he managed,

the Indian Smoke Shop (the “Shop”), which is located on the

Puyallup reservation. The investigation employed physical

and electronic surveillance, telephone toll records, trap and

trace devices on target telephones, a pole camera installed
UNITED STATES V. FLORES 5

outside the Shop, confidential informants, and controlled

purchases of pills by undercover agents and cooperators. The

investigation ended on October 20, 2009, when law

enforcement officers arrested Flores and his codefendants:

Bill C. Flores (“Flores Senior”), Flores’s father; Tiny BeanFlores (“Tiny Bean”), Flores’s half-brother and an employee

of the Shop; Danny Lee Sherwood (“Sherwood”), Flores’s

relative and an employee of the Shop; Timothy Morehead, a

purchaser; and Shelbie Ingham (“Ingham”), Flores’s

girlfriend at the time.

The same day, law enforcement officers searched the

Shop and Flores’s house pursuant to search warrants and

uncovered evidence of a drug conspiracy. Officers

discovered cash and two bottles of methadone, and a loaded

Smith and Wesson, Model 29, .44 Magnum revolver in an

unlocked drawer approximately one foot from a safe where

the officers recovered the bottles of methadone. The search

of Flores’s house yielded approximately seven empty

prescription bottles—five of which were for oxycodone and

all of which were prescribed to persons other than Flores.

Based on this evidence, Flores and his codefendants were

indicted and charged in 34 counts. Flores was indicted with

one count of conspiring to distribute oxycodone and

methadone in violation of 21 U.S.C. §§ 841(a)(1), (b)(1)(C),

and 846, five counts of substantive distribution of oxycodone

in violation of 21 U.S.C. §§ 841(a)(1), (b)(1)(C), one count of

possession with intent to distribute methadone in violation of

18 U.S.C. § 2 and 21 U.S.C. §§ 841(a)(1), (b)(1)(C), and one

count of possession of a firearm in furtherance of the

methadone count in violation of 18 U.S.C. §§ 2, 924(c)(1)(A).

TinyBean,Ingham, Morehead, and Flores Senior entered into

plea agreements. Flores and Sherwood proceeded to trial. A
6 UNITED STATES V. FLORES

 The jury acquitted Flores of conspiring to distribute methadone. 4

jury found Flores guilty of conspiring to distribute

oxycodone, distributing oxycodone, possessing methadone

with intent to distribute it, and possessing a gun in

furtherance of the methadone charge.4

In calculating Flores’s base offense level, Flores’s

Presentence Report (“PSR”) adopted a start date for the

conspiracy of October 2007 and estimated that the conspiracy

sold 1,000 to 1,500 80-milligram pills of oxycodone per day.

PSR recommended a two-level upward adjustment for use of

Shelbie Ingham, a person under eighteen years of age, in the

conspiracy. Flores filed objections to the PSR in his

sentencing memorandum. Specifically, he asserted that (1)

the PSR’s estimate of the quantity of drugs attributable to the

conspiracy was too high, and (2) there was no evidence to

support the enhancement for use of a minor.

At Flores’s sentencing hearing, Sherwood testified that he

joined the conspiracy in May 2009 and eventually sold up to

1,000 pills daily for Flores. The district court concluded that

a “conservative estimate” placed the start date of the

conspiracy in December 2007, based on an unindicted

coconspirator’s trial testimony. The court noted that it had

heard “a lot of testimony about the volume of the sales” and

concluded that 500 80-milligram pills of oxycodone was a

“conservative[]” estimate of the amount of pills that moved

through the conspiracy daily between December 2007 and

October 2009.

The district court explained that the marijuana equivalent

for that amount of oxycodone was “well over” 30,000

kilograms of marijuana, which is the smallest quantity that
UNITED STATES V. FLORES 7

 Federal sentencing courts use the Drug Quantity Table in § 2D1.1 of 5

the Federal Sentencing Guidelines to calculate the base offense level for

offenses involving controlled substances. Where, as here, an offense

involves a drug that is not listed in the Drug Quantity Table, sentencing

courts use the Drug Equivalency Tables in § 2D1.1 to covert the drug into

an equivalent amount of marijuana. See U.S. Sentencing Guidelines

Manual § 2D1.1 cmt. n.8(A) (2012). The Drug Equivalency Tables

provide that one gram of actual oxycodone equals 6,700 grams of

marijuana.

Here, using the district court’s start date of the conspiracy, December

2007, means the conspiracy lasted 689 days. Multiplying 689 days by the

district court’s estimate of 500 pills per day results in a total of 344,500

80-milligram pills. Multiplying this amount by the 80 milligrams in each

pill results in 27,560,000 milligrams, or 27,560 grams, of oxycodone.

Finally, after converting oxycodone to its marijuana equivalent using the

1:6,700 gram ratio in the Drug Equivalency Tables, the district court’s

adopted start date and daily quantity yield a total of 184,652 kilograms of

marijuana. Pursuant to the Drug Quantity Table, any amount of marijuana

over 30,000 kilograms results in the highest base offense level, which is

38.

triggers the highest base offense level, 38, in the Drug

Quantity Table. See U.S. Sentencing Guidelines Manual

§ 2D1.1 (Drug Quantity Table). The district court therefore 5

concluded that Flores’s base offense level was 38. The

district court imposed a four-level enhancement for Flores’s

leadership role in the conspiracy and a two-level

enhancement for use of a minor. However, the district court

did not make an express finding as to Ingham’s age at the

time of her involvement in the conspiracy. The court

imposed a two-level downward adjustment for Flores’s

acceptance of responsibility, resulting in a total offense level

of 42. The court correctly stated that the Guidelines range for

an offense level 42 and criminal history category I is 360

months to life.
8 UNITED STATES V. FLORES

The district court did not rely solely on the Guidelines

range in determining its ultimate sentence. Noting that the

Federal Sentencing Guidelines are advisory, the court

explained that the “big issue is not so much the math, the

calculations; it’s the qualitative issues that are so distressing

. . . . Maybe Shelbie Ingham was broken before Billy Miranda

Flores got his claws in her, but she is definitely broken now.”

The court also stated:

There is a lot of human wreckage in this case,

and we don’t even know how pervasive the

reach of this conspiracy went, not those who

agreed to perform sales, but just the reach of

the conspiracy, the people who bought, the

people who sold and more—most importantly,

those people who used.

The district court further opined that the “biggest challenge

for any judge who sentences someone” is determining the

difference between a criminal “who is ignorant or dumb or

stupid . . . [and] in need of a break” and those who “are really

bad.” “I put Billy Miranda Flores among that [latter] group”

because Flores “preys on people,” “has no empathy for other

people,” and “has harmed so many people.” Based on “the

seriousness of the offense, the personal characteristics, the

need to promote the rule of law and to deter people from

committing the same offenses that he has committed,” the

court imposed a total of 240 months of imprisonment—180

months of imprisonment on the drug charges, half of the lowend of the advisory Guidelines range, and 60 months on the

firearm offense, which is the mandatory minimum sentence

for a violation of 18 U.S.C. § 924(c).
UNITED STATES V. FLORES 9

Flores raises two issues on appeal relating to the

calculation of his Federal Sentencing Guidelines range. First,

Flores argues the district court erred in calculating the amount

of drugs attributable to the conspiracy by employing a

method that was not sufficiently reliable and by failing to “err

on the side of caution” as required by Ninth Circuit

precedent. Second, Flores asserts that the two-level

enhancement for use of a person under eighteen years of age

in the conspiracy was not supported by the record.

II

We first address Flores’s challenge to the district court’s

calculation of the drug quantity attributable to the conspiracy.

“When we review a sentence, the first step is to determine if

the district court made a material error in its Guidelines

calculation that serves as the starting point for its sentencing

decision.” Kilby, 443 F.3d at 1140 (citing United States v.

Cantrell, 433 F.3d 1269, 1280 (9th Cir. 2006)). If we find a

material error in the Guidelines calculation, “we will remand

for resentencing, without reaching the question of whether the

sentence as a whole is reasonable.” Kilby, 443 F.3d at 1140

(citation omitted). If the district court did not err in applying

the Guidelines, we then consider challenges to the

reasonableness of the overall sentence in light of the factors

specified in 18 U.S.C. § 3553(a). Id.

This Court reviews de novo “whether a district court’s

method of approximation of the relevant drug quantity

conforms to the Guidelines.” Id. (citing United States v.

Rosacker, 314 F.3d 422, 425 (9th Cir. 2002)). After United

States v. Booker, 543 U.S. 220 (2005), we review a district

court’s sentencing decisions, including its factual findings,

for abuse of discretion. Gall v. United States, 552 U.S. 38, 51
10 UNITED STATES V. FLORES

(2007); United States v. Carty, 520 F.3d 984, 993 (9th Cir.

2008) (en banc). Under the law of this Circuit, a district court

is required to resolve factual disputes regarding drug quantity

by applying the preponderance of the evidence standard.

Kilby, 443 F.3d at 1140; see Rosacker, 314 F.3d at 429–30

(holding the clear and convincing standard that applies to

cases where a sentencing factor has an extremely

disproportionate effect on the sentence does not apply to drug

quantity approximations).

Several different witnesses testified about the quantity of

drugs sold by the conspiracy. Most of the evidence at trial

relating to the quantity of drugs over the life of the conspiracy

came from codefendant Tiny Bean, unindicted coconspirators

Leslie Larson (“Larson”) and Dennis Hilsendeger

(“Hilsendeger”), law enforcement officers who surveilled the

Shop, and an undercover officer who made three controlled

buys from Flores. In addition, Sherwood testified at Flores’s

sentencing hearing regarding the amount of drugs Sherwood

sold for the conspiracy.

A short summary of the coconspirators’ testimony

relating to the quantity of drugs they individually sold for

Flores is useful here. Larson testified she began selling drugs

for Flores in approximately February of either 2007 or 2008,

while the other coconspirators testified they began selling for

Flores as early as January 2008 and as late as mid-2009.

Larson testified that she sold drugs for Flores for

approximately one year until her arrest on April 16, 2009.

Over this one-year period, Larson testified she started selling

a few pills per day and eventually increased to selling

hundreds of pills per day. Hilsendeger testified he sold pills

for Flores for approximately six months, starting with a few

pills a day in January or February 2008 and eventually
UNITED STATES V. FLORES 11

 Although 332 methadone pills were seized from Flores’s office, the 6

jury acquitted Flores of conspiring to distribute methadone. Thus, those

pills are not included in the quantity drugs attributable to the conspiracy

to distribute oxycodone.

increasing to 50 or 100 pills per day. Tiny Bean testified he

sold pills for Flores when Flores was out of town and sold

approximately 100 to 300 pills over ten or twelve weekends,

or 50 to 100 pills per day, but once sold around 1,000 pills

over one weekend. Sherwood testified he sold pills for Flores

for around six months starting in May 2009, though he

believed that Flores began selling pills in 2007. Sherwood

testified he sold hundreds of pills per day when he started and

eventually increased to 1,000 pills per day. Sherwood

estimated that eight to ten other persons sold drugs for Flores.

The witnesses testified they primarily sold 80-milligram pills.

The PSR estimated that the conspiracy sold 1,000 to

1,500 80-milligram pills per day from October 2007 through

October 2009. The district court adopted December 2007 as

the start date of the conspiracy and used 500 80-milligram

pills as a “conservative” estimate of the volume of oxycodone

pills moved by the conspiracy per day.

The accuracy of this estimate is important because the

applicable Guidelines range for a drug trafficking crime

depends upon the weight of drugs involved. United States v.

Culps, 300 F.3d 1069, 1076 (9th Cir. 2002); U.S. Sentencing

Guidelines Manual § 2D1.1(a), (c) (2004). Where, as here,

none of the total drugs allegedly sold by the conspiracy were

6

seized, the district court may approximate the weight of the

drugs. Kilby, 443 F.3d at 1141 (citing United States v.

August, 86 F.3d 151, 154 (9th Cir. 1996); U.S. Sentencing
12 UNITED STATES V. FLORES

 The comment provides: 7

In making this determination, the court may consider,

for example, the price generally obtained for the

controlled substance, financial or other records, similar

transactions in controlled substances by the defendant,

and the size or capability of any laboratory involved.

U.S. Sentencing Guidelines Manual § 2D1.1, cmt. n.5.

Guidelines Manual § 2D1.1, cmt. n.5). Because a sentence 7

will vary greatly based on these approximations, courts must

exercise caution in selecting the method of calculation and

meet the following criteria: (1) “the government is required

to prove the approximate quantity by a preponderance of the

evidence . . . [which means that] [t]he district court must

conclude that the defendant is more likely than not actually

responsible for a quantity greater than or equal to the quantity

for which the defendant is being held responsible”; (2) “the

information which supports an approximation must possess

sufficient indicia of reliability to support its probable

accuracy”; and (3) because the defendant’s “sentence depends

in large part upon the amount of drugs . . . and approximation

is by definition imprecise, the district court must err on the

side of caution” in approximating the drug quantity. Culps,

300 F.3d at 1076 (emphasis added) (internal quotation marks

and citation omitted); United States v. Walton, 908 F.2d 1298,

1302 (9th Cir. 1990) (“[W]hen choosing between a number

of plausible estimates of drug quantity, none of which is more

likely than not the correct quantity, a court must err on the

side of caution.”).

This Court previously has approved the “multiplier

method” employed by the district court, which estimates the

total quantity of drugs sold by “selecting a time period over
UNITED STATES V. FLORES 13

which it is more likely than not that the defendant was

dealing in that quantity and multiplying these two factors

together.” Culps, 300 F.3d at 1077 (holding the multiplier

method is an acceptable means of calculating drug quantity

“[p]rovided that the approximation has a reliable evidentiary

basis and that the court proceeds with caution”). Applying

the multiplier method in this case required the district court

to determine three data points: the length of the conspiracy,

the number of pills sold by the conspiracy per day, and the

tablet strength of the pills. We examine the district court’s

findings as to each data point.

We begin with the easiest data point first: the tablet

strength. Several witnesses involved in the conspiracy

testified they primarily sold 80-milligram pills, and no

witness contradicted this testimony. In addition, Flores sold

70 to 100 80-milligram pills to an undercover agent during

three controlled buys. Consequently, the district court’s

adoption of an average tablet strength of 80-milligrams was

not an abuse of discretion.

The next data point we consider is the quantity of drugs

attributable to the conspiracy per day. The district court

discounted its baseline estimate of 1,000 pills per day by fifty

percent to satisfy its duty to account for a margin of error.

See id. at 1081 (stating fifty percent reduction of baseline

estimate ordinarily will “satisfy the district court’s duty to err

on the side of caution[,]” assuming the amount being

discounted is founded on reliable evidence); cf. August,

86 F.3d at 154 (permitting the method of calculating “lab

capacity” as an approximation of the relevant amount of

drugs that “could have been produced during the course of

the offense”) (emphasis in original). There was scant

evidence at trial relating to the quantity of drugs sold during
14 UNITED STATES V. FLORES

 Only Larson both placed the date of the conspiracy during that time 8

period and provided information regarding the quantity of pills she sold

during that time. However, Larson stated she began selling pills in either

February 2007 or February 2008. Sherwood is the only other witness who

testified that the conspiracy began in 2007 (though he was not involved at

that time), but he provided no information regarding the amount of drugs

sold during that period. Several witnesses—Larson, Hilsendeger, and

Sherwood—testified they began selling small amounts of pills for Flores

in 2008 or 2009 and eventually increased their sales dramatically.

the earliest months of the district court’s selected time frame

for the conspiracy. There was, however, coconspirator 8

testimony attributing hundreds of pills per day to the

conspiracy from January 2008 through mid-2008 and then

even higher amounts for the months thereafter. The district

court’s estimate of 500 80-milligram pills per day is

supported by a preponderance of the evidence. Thus, the

district court did not abuse its discretion in estimating the

daily drug quantity attributable to the conspiracy.

Finally, as to the last data point, the length of the

conspiracy, the district court adopted a start date of December

2007. In selecting that date, the district court stated that it

relied on Larson’s testimony. Larson testified that she

purchased oxycodone from Flores for approximately one

year. At the sentencing hearing, the district court stated that

Larson was arrested in August 2008 and that nine or twelve

months before her arrest would place her entrance into the

conspiracy in “October to December 2007.” Later, the court

stated:

I believe the conspiracy began on or before

December 2007. Leslie Larson was arrested

in August [2008]. She was buying up to 300

pills per day from Billy Flores for 9 to 12
UNITED STATES V. FLORES 15

months at that time. Taking the conservative

estimate would put that in December 2007.

Thus, to arrive at December 2007 as the start date of the

conspiracy, the district court relied on August 2008 as the

date Larson was arrested and then counted backwards nine

months to reach December 2007.

The evidence at trial, however, does not support a finding

that Larson was arrested in August 2008. Although Larson

testified that law enforcement searched her apartment at some

unspecified date before her arrest, she stated that her “first

arrest” for selling drugs for Flores was not until April 16,

2009. Larson testified that she was arrested again in

November 2009 (the day after Thanksgiving) for not

appearing in court and then served six months of

imprisonment.

A district court may rely on a coconspirator’s testimony

where, as here, the testimony is given under oath and is

subject to cross-examination. See, e.g., United States v.

Alvarez, 358 F.3d 1194, 1213 (9th Cir. 2004) (holding three

coconspirators’ estimates of drug weight were sufficiently

reliable where they testified under oath and were subject to

cross-examination); United States v. Melchor-Zaragoza,

351 F.3d 925, 929 (9th Cir. 2003) (holding that a

coconspirator’s testimony that twenty-three aliens were taken

hostage by conspirators was sufficient to support court’s

finding, for sentencing purposes, that twenty-three victims

were involved in the conspiracy to commit hostage taking).

However, there is no evidence in the record to support the

district court’s finding that Larson was arrested in August

2008. Consequently, the district court’s December 2007 start

date of the conspiracy, which was based on the purported
16 UNITED STATES V. FLORES

August 2008 arrest, also is not supported by Larson’s

testimony.

Sherwood was the only other witness who testified that

Flores was selling drugs in 2007. In response to Government

questioning at the sentencing hearing, Sherwood confirmed

that he was not “aware of any time period from [an

unspecified date in 2007] until [Sherwood’s] arrest in 2009

when Billy Flores wasn’t selling pills.” The remaining

witnesses testified to entering the conspiracy in 2008 or 2009.

Of those witnesses, Hilsendeger testified to the earliest

involvement—in January or February of 2008.

The PSR placed the start date of the conspiracy in

October 2007, two months before the date the district court

adopted. A “court may adopt the factual findings of the

presentence report . . . [but] may not . . . adopt conclusory

statements unsupported by facts or the Guidelines.” United

States v. Navarro, 979 F.2d 786, 789 (9th Cir. 1992); see

United States v. Garcia-Sanchez, 189 F.3d 1143, 1149 (9th

Cir. 1999) (reversing estimate of conspiracy’s weekly drug

sales where government offered only agent’s unexplained

conclusions that did not contain “sufficient indicia of

reliability to support its probable accuracy” (citation

omitted)). Sherwood’s testimony gives the district court’s

determination that the conspiracy started in December 2007

some slight support. But even if the district court erred in

determining the start date, any error in the district court’s

calculation of the length of the conspiracy is harmless beyond

a reasonable doubt. See Alvarez, 358 F.3d at 1213 (holding

any error was harmless where, in order to lower defendant’s

base offense level, the quantity of drugs would have to drop

below an amount that was not supported by the record).

Selecting a start date, based on Hilsendeger’s testimony, of
UNITED STATES V. FLORES 17

January or February 2008 would result in the same base

offense level, as would adopting Flores’s suggested start date

of September 25, 2008. Indeed, even if the length of the

conspiracy were cut in half, the number of pills sold by the

conspiracy daily would have to drop below 170 80-milligram

pills to lower Flores’s base offense level from 38 to 36. Such

a drop is not supported by the record. Thus, a recalculation

of the Guidelines range by the district court based on a

shorter conspiracy length would not lead to a lesser base

offense level. See id. Consequently, any error by the district

court in calculating the quantity of drugs attributable to the

conspiracy is harmless. See Cantrell, 433 F.3d at 1280;

United States v. Scheele, 231 F.3d 492, 499–500 & n.4 (9th

Cir. 2000).

III

Flores next argues that the district court committed

procedural error in imposing a sentencing enhancement for

use of a person under eighteen years of age in the conspiracy.

Flores maintains there was no evidence in the record as to

Shelbie Ingham’s age at the time she entered the conspiracy.

We agree that the district court abused its discretion in

imposing this sentencing enhancement because the court

failed to set forth its reasons for finding that Ingham was a

minor when she participated in the conspiracy.

A

At trial, Flores testified that he met Shelbie Ingham

around November or December 2008. After meeting Ingham,

Flores said he did not see her for four to six months because

Ingham made his girlfriend at the time, Larson, “very upset,”

and Larson told Flores not to talk to Ingham. Flores started
18 UNITED STATES V. FLORES

talking to Ingham again after she brought her car to the Shop

for repairs. In his testimony, Flores admitted to selling

Ingham oxycodone in the summer of 2009, when she was

around eighteen years old. Tiny Bean testified he sold drugs

to Ingham sometime before he stopped selling drugs for

Flores in June 2009. In August or September 2009, law

enforcement made a controlled buy from Ingham. Flores

admitted to being intimate with Ingham “at the end,” before

he was arrested on October 20, 2009. Flores estimated that

Ingham turned eighteen about four months before she was

arrested, placing her birthday around June 2009.

The PSR recommended a two-level upward adjustment

for Flores’s use of “a person . . . less than 18 years of age to

commit the offense.” Flores’s PSR referred to Ingham as a

minor and stated that Ingham was addicted to pills and

became a member of the conspiracy to support her addiction.

Flores objected to the PSR’s characterization of Ingham as a

minor at the time she was involved in the conspiracy, arguing

there was no evidence to support that finding. The probation

office declined to amend the PSR, however, stating that its

information of Ingham’s age was based on the following

language from Ingham’s PSR: “Flores provided a residence

and vehicle for Ingham, who was the youngest member of the

conspiracy, and barely seventeen when she became involved

with Oxycontin and met Flores.”

In its Sentencing Memorandum, the Government did not

request an enhancement for use of a minor pursuant to

§ 3B1.4, nor did it allege facts demonstrating that Ingham

was a minor. It indicated at the sentencing hearing, however,

that it did not “disagree with the Court that there is evidence

there to find it.”
UNITED STATES V. FLORES 19

The district court failed to point to any evidence in the

record establishing Ingham’s age at the time of her

involvement in the conspiracy. During the sentencing

hearing, defense counsel argued that the enhancement for use

of a minor in the conspiracy should not apply, and the district

court responded: “I can tell you that . . . there’s a two-level

increase on use of a person under [eighteen]. I know that

from—I know [Ingham], and I know the circumstances.”

After listening to Sherwood’s testimony, the argument of

counsel, and Flores’s allocution, the district court imposed

the two-level enhancement for using a person less than

eighteen years of age in the conspiracy. The district court’s

vague statement about knowing Ingham and the

circumstances did not set forth any facts to justify the

imposition of the enhancement. 

B

Post-Booker, we review a district court’s sentencing

decisions, including its factual findings, for abuse of

discretion. Gall, 552 U.S. at 49; Carty, 520 F.3d at 993. A

two-level sentencing enhancement may be imposed under

United States Sentencing Guidelines Manual § 3B1.4 “[i]f the

defendant used or attempted to use a person less than eighteen

years of age to commit the offense or assist in avoiding

detection of, or apprehension for, the offense,” meaning that

the defendant directed, commanded, encouraged, intimidated,

counseled, trained, procured, recruited, or solicited the minor.

U.S.S.G. § 3B1.4 cmt. n.1 (2001). The district court may

impose the § 3B1.4 enhancement only if a preponderance of

the evidence demonstrates that the defendant “acted

affirmatively to involve the minor in the crime.” United

States v. Jimenez, 300 F.3d 1166, 1069 (9th Cir. 2002)

(quotation marks and citation omitted).
20 UNITED STATES V. FLORES

Because the district court did not provide a factual basis

for imposing the enhancement for use of a minor in the

conspiracy, we must determine whether an “adequate

explanation” can be “inferred from the PSR or the record as

a whole.” Carty, 520 F.3d at 992; see also United States v.

Jordan, 291 F.3d 1091, 1099 (9th Cir. 2002) (“A merely

speculative logic cannot displace the need for evidence on

[the question of whether a defendant’s conduct justified a

leadership-role enhancement], which cannot be decided by

assumption or inference not based on fact.”). Here, neither

the PSR nor the record supply an adequate explanation for

this enhancement.

At trial, Flores admitted that he conspired with Ingham to

sell oxycodone but denied that she was a minor when she

began selling for him. There was no other evidence at trial

regarding Ingham’s age when she entered the conspiracy.

The PSR refers to Ingham as a minor and states that Ingham

was addicted to pills and became a member of the distribution

conspiracy to support her own addiction. The Addendum to

the PSR, created in response to Flores’s objection, copied

language from Ingham’s PSR, which states that Flores

provided Ingham a residence and a vehicle and that she was

“barely seventeen when she became involved with Oxycontin

and met Flores.” This factual assertion does not support a

finding that she became a member of the conspiracy before

she reached the age of eighteen.

The first question, then, is whether these statements in the

PSR may serve as a proper basis for the district court’s

decision. This Court has held that a district court may rely on

an unchallenged PSR at sentencing to find by a

preponderance of the evidence that the facts underlying a

sentencing enhancement have been established. See United
UNITED STATES V. FLORES 21

States v. Charlesworth, 217 F.3d 1155, 1160–61 (9th Cir.

2000) (where defendant failed to challenge accuracy of

information in presentence report and failed to offer any

evidence to contradict presentence report, sentencing court

did not err in relying on presentence report in denying

defendant’s request for sentence reduction); United States v.

Marin-Cuevas, 147 F.3d 889, 895 (9th Cir. 1998). However,

the district court “may not . . . adopt conclusory statements

unsupported by the facts or the Guidelines.” Culps, 300 F.3d

at 1078 (citations omitted) (holding a conclusory statement in

a PSR regarding the average transaction size in a drug

conspiracy could not sustain district court’s adoption of that

size where “the factual underpinning for that assertion, if any,

was not explained”).

The record does not provide an explanation of the factual

underpinning for the assertion in the PSR that Ingham was a

minor when she participated in the conspiracy. Flores

objected to the PSR and argued there was no evidence of

Ingham’s age when she joined the conspiracy. He did not

submit evidence regarding her age when she joined the

conspiracy. Flores’s failure to submit such evidence is not

dispositive. We previously have held that “when a defendant

raises objections to the PSR, the district court is obligated to

resolve the factual dispute, and the government bears the

burden of proof . . . . The court may not simply rely on the

factual statements in the PSR.” United States v. Showalter,

569 F.3d 1150, 1160 (9th Cir. 2009) (emphasis added) (citing

United States v. Ameline, 409 F.3d 1073, 1085–86 (9th Cir.

2005) (en banc); Fed. R. Crim. P. 32(i)(3)(B) (requiring court

to rule on disputed matters at sentencing)). Thus, Flores’s

failure to provide additional evidentiary support for his

contention did not alter the district court’s obligation to
22 UNITED STATES V. FLORES

 In its answering brief, the Government states that Ingham’s birthday 9

“was in July 2009.” The Government determined Ingham’s birthday by

looking at Ingham’s Presentence Report, “to which the district court had

access.” Ingham’s PSR is not properly before this Court, however,

because it was not in the record below. The Government alternatively

argues that the PSR Addendum provided Flores access to the relevant

information from Ingham’s PSR regarding her age. This is incorrect,

however, because the Addendum did not include Ingham’s birthday nor

did it state that she was a minor when she became involved in the

conspiracy. Additionally, the district court could not base its conclusions

regarding Ingham’s age and her involvement in the conspiracy on

information to which Flores was not privy. See Appellant’s Opening Br.

at 34 (noting that defense counsel did not have access to Ingham’s sealed

PSR). During oral argument, the Government claimed that Ingham’s

Sentencing Memorandum states that her birthday is July 9, 1991. This

may be true, but even if that memorandum were part of the record in this

case, whether Ingham’s birthday was in June or July 2009 is immaterial,

because there is no evidence in the record that establishes by a

preponderance that Ingham participated in the conspiracy before July

2009.

resolve this factual dispute nor excuse the Government’s

failure to meet its burden of proof.

The evidence in the record similarly does not provide the

necessary factual underpinning for imposing the

enhancement. The only evidence in the record of Ingham’s

age came from Flores, who estimated that she turned eighteen

in June 2009. None of the events the Government relies on 9

to connect Ingham to the conspiracy took place before June

2009. The Government identifies activities that took place in

the “summer,” but “summer” falls both before and after

Ingham’s birthday. Nor does evidence that Ingham was

“close” with Flores or in a relationship with him before she

turned eighteen establish by a preponderance of the evidence

that she was involved in the conspiracy at that time. The only

evidence affirmatively linking Ingham to the conspiracy—as
UNITED STATES V. FLORES 23

opposed to merely linking her to Flores—was law

enforcement’s controlled purchase from Ingham in September

2009, which occurred after June 2009, the month Flores

testified that Ingham’s eighteenth birthday took place. In

addition, the PSR does not, contrary to the Government’s

assertion, state that Ingham was seventeen when she “became

involved in the conspiracy,” only that she was seventeen

when she became involved with Oxycontin and met Flores.

Ingham’s addiction to OxyContin and her relationship with

Flores when she was seventeen do not demonstrate that

Ingham joined the conspiracy at that time. Therefore, we

conclude that the Government did not meet its burden of

establishing that Ingham was a minor when she participated

in conspiracy.

When a party raises a specific, non-frivolous argument

that is relevant to sentencing, “the judge should normally

explain why he accepts or rejects the party’s position.”

Carty, 520 F.3d at 992–93 (citation omitted). The district

court’s failure to do so is not procedural error where

“adequate explanation” may “be inferred from the PSR or the

record as a whole.” Id. at 992. The factual basis for the

district court’s imposition of the enhancement here cannot be

inferred from the PSR or the record as a whole. See Gall,

552 U.S. at 50 (“[A court] must adequately explain the

chosen sentence to allow for meaningful appellate review

 . . . .”). The district court provided no factual basis for its

conclusion and failed to resolve a factual dispute raised by

Flores. The facts in the PSR are inconclusive as to whether

Ingham was a minor when she joined the conspiracy, and the

trial record does not illuminate the issue. On this limited

evidentiary record, we cannot conclude that this enhancement

was supported by a preponderance of the evidence. Thus, we

must conclude that the district court abused its discretion by
24 UNITED STATES V. FLORES

imposing the enhancement without providing an adequate

factual basis.

C

The Supreme Court has held that improperly calculating

the Guidelines range may constitute “significant procedural

error.” Gall, 552 U.S. at 51. Thus, even where, as here, the

district court imposes a sentence well below the Guidelines

range, it is difficult, if not impossible, to determine whether

the court would impose the same sentence if it were to heed

its imperative to keep the Guidelines range “in mind

throughout the process.” Carty, 520 F.3d at 991; Gall,

552 U.S. at 50 n.6 (“[D]istrict courts must begin their analysis

with the Guidelines and remain cognizant of them throughout

the sentencing process.”);United States v. Munoz-Camarena,

631 F.3d 1028, 1031 (9th Cir. 2011) (declining to find

harmless a district court’s incorrect application of an

enhancement, even though the district court sentenced the

defendant above the Guidelines range and stated it would

have imposed the sentence no matter the Guidelines

calculation, because the Ninth Circuit was not convinced that

the district court would impose the same sentence if the

correct Guidelines range were “kept in mind throughout the

process”) (citation omitted).

In this case, the district court calculated Flores’s total

offense level as 42, which resulted in a Guidelines range of

360 months to life. Removing the incorrect two-level

enhancement would result in a correct total offense level of

40, with an associated Guidelines range of 292 to 365

months. Although the two Guidelines ranges overlap slightly

and the district court sentenced Flores to 180 months for the

drug charges, which is below both the original and the correct
UNITED STATES V. FLORES 25

Guidelines ranges, we cannot say whether the district court

would impose the same sentence if it kept the correct

Guidelines range in mind throughout the process. See

Munoz-Camarena, 631 F.3d at 1031. Because we conclude

that material errors affected the district court’s Guidelines

calculation that served as the starting point for its sentencing

decision, we must vacate Flores’s sentence and remand this

matter for resentencing. Because we remand on a procedural

error, we decline to reach Flores’s argument regarding the

substantive reasonableness of his sentence. See Gall,

552 U.S. at 51 (holding that “the appellate court must . . . first

ensure that the district court committed no significant

procedural error” and should consider whether the sentence

is substantively reasonable only if “the district court’s

sentencing decision is procedurally sound”); Kilby, 443 F.3d

at 1140 (“If there is a material error in the Guidelines

calculation, we will remand for resentencing, without

reaching the question of whether the sentence as a whole is

reasonable . . . in light of the factors specified in 18 U.S.C.

§ 3553(a).”).

D

Finally, the parties dispute whether we should allow the

district court to consider new evidence on remand. The

default rule is that “if a district court errs in sentencing, we

will remand for resentencing on an open record—that is,

without limitation on the evidence that the district court may

consider.” United States v. Matthews, 278 F.3d 880, 885–86

(9th Cir. 2002) (en banc) (“On remand, the district court

generally should be free to consider any matters relevant to

sentencing, even those that may not have been raised at the

first sentencing hearing, as if it were sentencing de novo.”

(citing United States v. Ponce, 51 F.3d 820, 826 (9th Cir.
26 UNITED STATES V. FLORES

1995); United States v. Caterino, 29 F.3d 1390, 1394 (9th

Cir. 1994))). We may depart from this general rule where

“‘additional evidence would not have changed the outcome

or where there was a failure of proof after a full inquiry into

the factual question at issue.’” Culps, 300 F.3d at 1082

(quoting Matthews, 278 F.3d at 886); see also United States

v. Reyes-Oseguera, 106 F.3d 1481, 1484 (9th Cir. 1997)

(remanding for resentencing on a closed record where

government offered insufficient evidence to support a

reckless endangerment enhancement).

Here, we cannot conclude that there was a full inquiry

into the factual question at issue or that it would be futile to

introduce additional evidence regarding Ingham’s birthday

and her participation in the conspiracy. The Government did

not request an enhancement for use of a minor in its

sentencing memorandum. Rather, the enhancement was

recommended by the probation office and imposed sua sponte

by the district court at the sentencing hearing before the court

heard argument from the Government. The Government

stated it did not disagree with the district court that there was

evidence to support the enhancement, but did not present any

evidence in support of the district court’s finding. Under

these circumstances, we leave it to the district court’s

discretion to “assess the government’s right to submit further

evidence on this issue.” Jordan, 291 F.3d at 1029; see also

United States v. Gonzales, 207 F.3d 906, 914 (9th Cir. 2002)

(leaving the question whether to allow new evidence upon

resentencing to the district court’s discretion where the

court’s initial inquiry was incomplete). We remand to the

district court with directions to reconsider its sentencing

decision regarding the enhancement for use of a minor.

VACATED and REMANDED for resentencing.