United States v. Law

United States Court of Appeals
FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued February 1, 2008 Decided June 13, 2008

No. 05-3091

UNITED STATES OF AMERICA,
APPELLEE

v.

NATHANIEL LAW,
APPELLANT
________

Consolidated with
05-3092, 05-3120
________

Appeals from the United States District Court
for the District of Columbia
(No. 03cr00311-01)
(No. 03cr00311-02)
(No. 03cr00311-04)
________

Robert A. Ratliff argued the cause and filed briefs and
Jonathan Zucker filed a brief for appellant William Farrell.

Michael T. Morley argued the cause for appellant
Nathaniel Law. With him on the briefs was Katherine Leong.
 2
Joseph Virgilio, appointed by the court, argued the cause
and filed the briefs for appellant Carroll Fletcher.

Katherine M. Kelly, Assistant U.S. Attorney, argued the
cause for appellee. With her on the brief were Jeffrey A.
Taylor, U.S. Attorney, and Roy W. McLeese, III, Mary B.
McCord, Kenneth F. Whitted, and George P. Eliopoulos,
Assistant U.S. Attorneys. John P. Gidez, Assistant U.S.
Attorney, entered an appearance.

Before: GINSBURG, BROWN, and KAVANAUGH, Circuit
Judges.

Opinion for the Court filed PER CURIAM.

PER CURIAM: Appellants William Farrell, Nathaniel Law,
and Carroll Fletcher were convicted by a jury of conspiring to
traffic in narcotics and of numerous related crimes. Each
appellant raises a number of objections to his convictions and
sentence. We affirm in all respects except that we reverse
Farrell’s conviction for conspiring to launder money, one of
Law’s convictions for distributing cocaine base, and
Fletcher’s conviction for maintaining a drug residence. The
cases are remanded to the district court for re-sentencing
consistent herewith.

I. Background

In the fall of 2000, the Federal Bureau of Investigation
launched a three-year investigation into the appellants’
trafficking in narcotics. The FBI initially gathered
information about the appellants’ operations by monitoring
their communications and learning of several locations they
used, including a recreation center at 4th St. and Rhode Island
Ave. N.E. (the Center), the Shiloh Baptist Church at 9th St.
and P St. N.W., a four-unit apartment building at 2002
Rosedale St. N.E., an apartment at 200 K St. N.W., and a
 3
KFC restaurant at Florida Ave. and North Capitol St. N.E.
Through its continued monitoring of the appellants’
communications and of these locations, the FBI gathered
evidence against the appellants and others, including Thomas
Jackson, Ricardo Atcherson, Renaldo Mason, Harry Jackson,
Ronald Valentine-Bey, and Lynn Cyrus. Thomas Jackson,
Atcherson, Mason, Harry Jackson, Valentine-Bey, and Cyrus,
all of whom then provided further information about the
appellants’ activities, participated in controlled purchases
from the appellants, and testified at trial.

The Government introduced compelling evidence that the
appellants distributed powder cocaine, cocaine base (also
known as crack cocaine) and heroin on numerous occasions
and that they did so pursuant to an agreement among
themselves. For example, Thomas Jackson testified that
Farrell ordinarily dealt with “the connection,” meaning the
source of their drugs, but for a time Farrell, afraid the police
were monitoring his actions, had Fletcher deal with the
source. During that period, Thomas Jackson bought 15
kilograms or more of powder cocaine from Fletcher. After
Fletcher failed to pay the connection as required, Farrell
resumed control over relations with the connection, and
Fletcher introduced Thomas Jackson to Farrell so that
Fletcher “won’t be in the middle of it” anymore. Thomas
Jackson testified he bought more than three kilograms of
powder cocaine from Farrell. Harry Jackson testified Fletcher
sold heroin to him twice and arranged for Farrell to sell
heroin to him once. Cyrus often bought crack cocaine from
Fletcher, who was sometimes accompanied by Law. On one
occasion, Fletcher arranged for Cyrus to buy 62 grams of
crack cocaine from Law. Mason testified Law sold him at
least nine kilograms of powder cocaine between late 2000 and
early 2003 and at least 250 grams of heroin in the summer of
2003. Mason also testified that when he would ask Law for
narcotics, Law would first call Farrell, and sometimes Farrell
 4
would accompany Law to the transaction; indeed, Law told
Mason that Farrell was his source.

Throughout the period of the conspiracy, Karlene
Thomas owned the Rosedale building, but from 1993 until at
least September 2001, she relinquished control over the
building to her former boyfriend, Nathaniel Moore. He in
turn gave control to Farrell, who made the monthly mortgage
payment of about $600 in Karlene Thomas’s name and
collected and kept the rent from the tenants. Law resided in
apartment #3 in the Rosedale building. In 2002, FBI agents
arrested Law and then searched his apartment pursuant to a
valid warrant. The agents discovered various drug-related
items, such as a scoop, the box to a coffee grinder, and digital
scales, each with a residue of crack cocaine on it.

During their search of Law’s apartment, the agents also
discovered that a key they had seized from Law during his
arrest fit the lock to apartment #4, which was across the hall
from Law’s apartment. The agents called Karlene Thomas,
who consented to their search of that apartment. There they
found 15 grams of crack cocaine, 17.7 grams of heroin,
business cards for Farrell and Fletcher, a loaded shotgun, and
various drug-related items, such as razor blades, syringes, a
strainer, a coffee grinder that matched the coffee grinder box
found in Law’s apartment, and digital scales, each with a
residue of crack cocaine on it.

FBI agents and Metropolitan Police officers also found
incriminating evidence when they arrested Farrell and
searched his home. In November 2003, an officer conducting
a traffic stop of Farrell seized $3,411, of which $3,030 was in
bills the FBI had provided to Mason earlier that day for a
controlled drug purchase from Farrell and Law. About a
week later, Farrell recovered the $3,411 from the police by
presenting a receipt for a savings bond in the amount of
 5
$10,368, which he had cashed shortly before the money was
seized. Three days later, agents executed a search warrant at
Farrell’s home, where they found more than $19,000 in cash,
$1,100 of which was in bills used by Mason in the
aforementioned controlled purchase. Agents also found a
gun, money order receipts in Karlene Thomas’s name for
mortgage payments on the Rosedale building, and various
drug-related items, such as plastic baggies, a scale, and paper
face masks.

As these facts suggest, and as the jury found, Farrell was
the leader of the conspiracy. He controlled the Rosedale
building, at which the appellants conducted some of their
drug activities. Law and Fletcher often consulted Farrell
before entering into a transaction. And Farrell managed the
connection.

The appellants were arrested late in 2003. A grand jury
indicted them on a number of charges, as follows:

• Count 1: Farrell, Law, and Fletcher were charged under
21 U.S.C. §§ 841 and 846 with conspiring to possess
with intent to distribute and conspiring to distribute five
kilograms or more of cocaine, 50 grams or more of
cocaine base, and 100 grams or more of heroin.1

• Count 2: Farrell was charged under 18 U.S.C. § 1956
with conspiring to launder the proceeds of his drug
transactions by making mortgage payments on the
Rosedale building in Karlene Thomas’s name.

1
Count 1 also charged Jeffrey Dunbar and Caul Watson with
the conspiracy and Count 4 also charged Watson with maintaining
a drug residence at 200 K St. N.W. The jury acquitted Dunbar and
Watson pleaded guilty and has not appealed.
 6
• Count 3: Farrell, Law, and Fletcher were charged under
21 U.S.C. § 856 with maintaining a residence (the
Rosedale building) for the purpose of manufacturing,
distributing, and using a controlled substance.

• Count 4: Fletcher was charged under 21 U.S.C. § 856
with maintaining a residence (the apartment at 200 K St.
N.W.) for the purpose of manufacturing, distributing, and
using a controlled substance.

• Count 5: Fletcher was charged under 21 U.S.C. § 841
with distributing 50 grams or more of cocaine base
through a purchase made by Cyrus.

• Counts 6-11: Law was charged under 21 U.S.C. § 841
with six counts of distributing five grams or more of
cocaine base, to wit, six controlled purchases made by
Atcherson.

• Count 12: Law was charged under 21 U.S.C. § 860
with distributing cocaine base within 1,000 feet of a
school through a controlled purchase made by Atcherson.

• Count 13: Farrell, Law, and Fletcher were charged
under 18 U.S.C. § 2 and 21 U.S.C. § 841 with possessing
with intent to distribute five grams or more of cocaine
base, which was discovered in apartment #4 of the
Rosedale building.

• Count 14: Farrell and Law were charged under 21
U.S.C. § 841 with distributing cocaine through a
controlled purchase made by Mason.

• Count 15: Farrell was charged under 21 U.S.C. § 841
with distributing cocaine through a controlled purchase
made by Valentine-Bey.
 7
The jury acquitted Fletcher on Count 3 but convicted the
appellants of all other counts. In a special verdict, the jury
also found Farrell was “an organizer or leader” of a drug
trafficking organization, which increased by four his offense
level for purposes of sentencing, see U.S. SENTENCING
GUIDELINES MANUAL (U.S.S.G.) § 3B1.1(a) (2007); and that
Farrell should forfeit assets in an amount equal to the
proceeds of his drug trafficking offenses in Counts 1, 14, and
15 ($874,800) and the funds involved in the money
laundering offense in Count 2 ($28,560), see 21 U.S.C.
§ 853(a); 18 U.S.C. § 982(a)(1).

The district court sentenced Farrell to 324 months in
prison on each of Counts 1, 13, 14, and 15, and to 240 months
in prison on each of Counts 2 and 3, all sentences to run
concurrently. The district court sentenced Law to life in
prison without release on Count 1 and concurrently to 212
months in prison on each of Counts 3 and 6-14. Finally, the
district court sentenced Fletcher to life in prison without
release on Counts 1 and 5, 240 months in prison on Count 4,
and 250 months in prison on Count 13, all sentences to run
concurrently. Law’s and Fletcher’s sentences on Counts 1
and 5 were enhanced to life in prison without release as
mandated by 21 U.S.C. § 841(b)(1)(A) because they each had
“two or more prior convictions for a felony drug offense.”

The appellants raise a variety of challenges to their
convictions and sentences. We address each appellant’s
arguments in turn.

II. William Farrell

Farrell advances several challenges to his convictions and
sentences. First, he claims the evidence was insufficient to
support his conviction for conspiring to launder money. We
agree and therefore reverse that conviction. Second, he
 8
argues the district court erred in admitting evidence that he
had failed to file federal income tax returns. Even if that was
an error, it was either harmless or moot, depending upon
which conviction is at issue. Third, Farrell argues the district
court erred in permitting the use of two particular binder tabs
accompanying the transcripts of the recorded conversations
played at trial. We find no such error. Fourth, Farrell
contends his sentences were unreasonably harsh. This
contention lacks merit. Finally, Farrell joins both of
Fletcher’s challenges to the Government’s expert opinion
testimony, which, as discussed in Part IV, we reject.

A. The Conspiracy to Launder Money

At trial, the Government argued and the jury found
Farrell had agreed with Fletcher to launder the proceeds of
their narcotics activities by using those proceeds to pay the
mortgage on the Rosedale building, which was owned by
Karlene Thomas. Farrell contends the evidence was not
sufficient to support the jury’s verdict. “We review the
sufficiency of the evidence de novo, considering it in the light
most favorable to the government, to determine whether any
rational trier of fact could have found [the defendant] guilty
beyond a reasonable doubt of all the required elements of the
crime.” Valdes v. United States, 475 F.3d 1319, 1322 (D.C.
Cir. 2007) (en banc).

The federal money-laundering statute proscribes the
“conversion of cash into goods and services as a way of
concealing or disguising the [illegal] wellspring of the cash.”
United States v. Wynn, 61 F.3d 921, 924 (D.C. Cir. 1995)
(quotation marks omitted).2 We have emphasized that 18

2
More precisely, the statute in relevant part punishes one who,
“knowing that the property involved in a financial transaction
represents the proceeds of some form of unlawful activity, conducts
 9
U.S.C. § 1956 “prohibits the laundering of money, not merely
the spending of money obtained illegally. Thus, the
Government must prove that [the subject transaction was]
motivated by a desire to conceal or disguise the source or the
ownership of the money.” Id. (citation omitted); see also
United States v. Hall, 434 F.3d 42, 50 (1st Cir. 2006) (“the
money laundering statute does not criminalize the mere
spending or investing of illegally obtained assets”).
Accordingly, it is generally the case that “[i]f transactions are
engaged in for present personal benefit, and not to create the
appearance of legitimate wealth, they do not violate the
money laundering statute.” United States v. Majors, 196 F.3d
1206, 1213 (11th Cir. 1999) (quotation marks omitted); cf.
Cuellar v. United States, No. 06-1456, 2008 U.S. LEXIS
4698, at 15-19 (U.S. June 2, 2008) (holding
§ 1956(a)(2)(B)(i), which prohibits transportation designed to
conceal certain attributes of illegally obtained funds, does not
require proof that defendant attempted to create appearance of
legitimate wealth, but recognizing such attempt may signal
violation of money laundering statute and indeed is manner in
which “classic money laundering” occurs). The statute also
punishes as a principal anyone who conspires to launder
money. § 1956(h).

Farrell argues the evidence was insufficient to show the
mortgage payments were designed to conceal the source of
the funds rather than to “profit[] from the excess rental
income or[ to] maintain[] the premises to further drug
trafficking.” To be sure, the Government’s evidence “need

or attempts to conduct such a financial transaction which in fact
involves the proceeds of specified unlawful activity [while]
knowing that the transaction is designed in whole or in part to
conceal or disguise the nature, the location, the source, the
ownership, or the control of the proceeds of specified unlawful
activity.” 18 U.S.C. § 1956(a)(1)(B)(i).
 10
not exclude every reasonable hypothesis of innocence or be
wholly inconsistent with every conclusion except that of
guilt.” United States v. Lam Kwong-Wah, 924 F.2d 298, 302
(D.C. Cir. 1991) (quotation marks omitted). But when faced
with an innocent explanation sufficiently supported by the
evidence to create a reasonable doubt about the defendant’s
guilt, the Government’s burden is to present evidence
sufficient to dispel that doubt. The need for evidence that
excludes such an innocent explanation is especially important
in relation to a charge of money laundering because of the
fine line between laundering and merely spending illicit
funds.

Both of Farrell’s innocent explanations create a
reasonable doubt about his guilt such that no reasonable jury
could conclude that Farrell’s purpose in paying the mortgage
on the Rosedale building was to conceal the source of
illegally obtained funds. First, the evidence showed that
Farrell profited from the excess rental income derived from
the building. The monthly mortgage payment on the
Rosedale building was about $600. The monthly rent for
each apartment in the Rosedale building, which Farrell
collected when he was paying the mortgage, was typically
$400 or $450. Although all the apartments were not always
rented, it is easy to see that Farrell’s rental income exceeded
his mortgage payments, making his decision to take over the
mortgage a profitable one. Second, the evidence showed
Farrell maintained the Rosedale building to further his drug
trafficking, for which maintaining he was in fact convicted on
Count 3. As detailed below, Farrell’s paying the mortgage
and collecting the rent were integral to the control he exerted
over the Rosedale building. In sum, there was ample
evidence to show Farrell paid the mortgage to gain present
benefits, not to create the appearance of legitimate wealth.
 11
At trial, the Government presented and now points to
three pieces of evidence intended to show Farrell paid the
mortgage in order to conceal the source of his funds. We find
the Government’s evidence insufficient to its task – it neither
makes for a strong affirmative case nor tends to exclude
Farrell’s innocent explanations.

First, the Government notes Farrell paid the mortgage in
Karlene Thomas’s name rather than in his own. Farrell did
this sometimes by purchasing a money order in Thomas’s
name and then making the money order payable to the
mortgagee, and sometimes by giving the money to Thomas to
make the payment. The Government cites two decisions in
which a court of appeals upheld the conviction of a person
who had laundered money by making a payment in another’s
name. Those cases, however, involved circumstances that
tended to exclude the possibility that the defendant was
merely spending the illicit funds. In neither case was there
any plausible legitimate reason for using another’s name. In
both cases the pseudonymous purchase provided the
defendant no benefit other than a way to convert the illegally
obtained funds; that is, the purchase merely created the
appearance of legitimate wealth. Indeed, in one case the
defendant admitted he was trying to launder the money. See
Wynn, 61 F.3d at 925-26 (one defendant obtains and uses
cashier’s checks in other defendant’s name to buy luxury
vehicle and soon thereafter to pay difference between trade-in
value of that vehicle and price of another); Hall, 434 F.3d at
52-53 (defendant bought truck with money order in sister’s
name and told acquaintance account from which funds came
was “fictitious ‘inheritance account’ in which the money ‘was
cleaned’”).

No such circumstance is present in this case. There was
a simple, benign reason for paying the mortgage in Thomas’s
name: Thomas was the mortgagor, making it easier for Farrell
 12
to pay the mortgage in her name than to make clear to the
mortgage company that payments in his name were to be
applied to her mortgage. And, as discussed above, making
the mortgage payments provided Farrell with legitimate
benefits, namely, rental income and a base for his drug
operation. Therefore, under the circumstances Farrell’s
decision to pay the mortgage in Thomas’s name does not
reasonably suggest a purpose to conceal the source of the
funds. Cf. United States v. Sanders, 928 F.2d 940, 946 (10th
Cir. 1991) (insufficient evidence of purpose to conceal where
defendant purchased cars in daughter’s name but defendant
was “present at these purchases[, was] readily identified by
the respective salespersons involved,” and “conspicuously”
used the cars).

Second, the Government points to Farrell’s alleged
“belief that, by paying the mortgage from 1993 to 2001, he
acquired a property interest in the building.” The
Government does not, however, explain how this alleged
belief shows a design to conceal the source of the funds. We
find this alleged belief has little or no probative value because
it does not distinguish mere spending from laundering;
legitimate spending to pay for real estate ordinarily comes
with the expectation of acquiring a property interest.

Third, the Government emphasizes that Farrell “refuse[d]
to deal with government entities regarding the Rosedale
building, such as paying sanitation bills or helping with tax
filings, and [refused] to provide Thomas with money to
handle such bills.”3 Left again to grope for the significance of
this allegation, we find none. For starters, this allegation

3
We understand the evidence to show, and the Government’s
position to be, that Farrell refused to pay for the preparation of “tax
papers” for the building, not that he refused to pay the taxes on the
building.
 13
relates not to the use (and thus possible cleansing) of the
illicit funds but rather to the funds’ non-use, the significance
of which is at best unclear. Moreover, Farrell’s refusal to pay
sanitation and tax-preparation bills may have reflected
nothing more than his desire to avoid diminishing the profit
from his investment in the Rosedale building. If Thomas was
willing to pay these bills even while Farrell was collecting the
rent, then Farrell had no incentive to pay them. Or Farrell
may have avoided paying the bills because he did not want
his name associated with a building he knew was used for
drug activities.

In sum, no reasonable jury could conclude that Farrell’s
purpose in paying the mortgage on the Rosedale building was
to conceal the source of illegally obtained funds. We
therefore vacate Farrell’s conviction on Count 2 for
conspiring to launder money.4

B. The IRS Records

Farrell contends the district court erred in admitting into
evidence certified statements by the IRS that he had not filed
income tax returns for the years 1998 through 2002. The
district court admitted these statements not to prove Farrell
was guilty of tax evasion but rather to rebut Farrell’s
contention that he had “legitimate income and not illegitimate
income” from “drug trafficking.” Under Federal Rule of
Evidence 404(b), evidence of other “crimes, wrongs, or acts is
not admissible to prove the character of a person in order to
show action in conformity therewith,” but it may be
admissible for another purpose. Because the introduction of
such evidence runs the risk the jury will convict the defendant

4
In consequence, we need not reach Farrell’s contention that
the evidence was insufficient to establish an agreement with
Fletcher to commit this offense.
 14
simply for being a bad person, the district court must be alert
to whether the probative value of the evidence is
“substantially outweighed by the danger of unfair prejudice,”
in which case the court must exclude it. FED. R. EVID. 403.
“We accord substantial deference to the district court’s
rulings on these issues.” United States v. Lawson, 410 F.3d
735, 741 (D.C. Cir. 2005); see also Henderson v. George
Wash. Univ., 449 F.3d 127, 133 (D.C. Cir. 2006) (“the
appellate court is extremely wary of second-guessing the
legitimate balancing of interests undertaken by the trial
judge” pursuant to Rule 403).

Farrell contends admitting the IRS records violated both
Rule 404(b) and Rule 403. He argues the IRS records were
inadmissible under Rule 404(b) because they were “probative
of nothing more than that [he] just was a tax deadbeat and he
was a bad citizen.” Farrell argues the evidence was
inadmissible under Rule 403 because whatever probative
value it might have had was “substantially outweighed by the
danger of unfair prejudice,” specifically the risk that the
evidence would unfairly suggest he was the “type of
dishonest person” who would deal drugs near a church or
launder money. As Farrell points out, the district court did
not give a limiting instruction as to the purpose for which the
IRS records were admitted.

We need not decide whether the district court erred, as
Farrell claims. To the extent the purported errors relate to
Farrell’s conviction on Count 2 for money laundering, they
are moot because we reverse that conviction on a different
ground, supra. To the extent they relate to Farrell’s drug-
related convictions on Counts 1, 3, and 13-15, they were
harmless. An error is harmless and thus to be disregarded if it
“does not affect substantial rights.” FED. R. CRIM. P. 52(a);
see 28 U.S.C. § 2111.
 15
In determining whether an error is harmless, the court
measures the harm in terms of whether the error had
substantial and injurious effect or influence in
determining the jury’s verdict, not merely whether the
record evidence [would be] sufficient absent the error to
warrant a verdict of guilt. Consequently, an evidentiary
error is harmless if ... the case is not close ....

Ashcraft & Gerel v. Coady, 244 F.3d 948, 953 (D.C. Cir.
2001) (quotation marks and citation omitted). Of course, “the
Government bears the burden of proving an error is
‘harmless.’” United States v. Perry, 479 F.3d 885, 891 (D.C.
Cir. 2007).

In this case, none of the drug charges was “close”; the
Government presented overwhelming evidence of Farrell’s
guilt on each drug-related count, to wit:

Count 1: The Government was required to prove Farrell
agreed “knowingly or intentionally ... to ... distribute ... or
possess with intent to ... distribute” five kilograms or more of
powder cocaine, 50 grams or more of crack cocaine (i.e.,
cocaine base), or 100 grams or more of heroin. See 21 U.S.C.
§§ 841(a)(1), (b)(1)(A)(ii)-(iii), (b)(1)(B)(i) & 846. We
detailed in Part I some of the evidence in support of this
charge: Farrell and Fletcher coordinated their dealings with a
drug source, their sales of powder cocaine to Thomas
Jackson, and their sale of heroin to Harry Jackson; Farrell and
Law jointly sold powder cocaine to Mason; and Law told
Mason that Farrell was his source for the powder cocaine and
heroin he was selling to Mason. The evidence in support of
the other drug counts, which we consider presently, also
shows Farrell’s participation in the conspiracy.

Count 3: The Government was required to prove Farrell
“knowingly open[ed], lease[d], rent[ed], use[d], or
 16
maintain[ed]” the Rosedale building “for the purpose of
manufacturing, distributing, or using” powder cocaine, crack
cocaine, or heroin. See 21 U.S.C. § 856(a). As detailed in
Part I, both apartment #3, which was rented by Farrell’s co-
conspirator Law, and apartment #4, which was evidently not
rented, contained drugs and drug paraphernalia. Apartment
#4 also contained links to Farrell, as well as to Fletcher and
Law, specifically, Farrell’s and Fletcher’s business cards and
a coffee grinder matching a piece of a coffee grinder in Law’s
apartment. And although Karlene Thomas was the Rosedale
building’s owner of record, Farrell had effective control. Not
only was he collecting the rent from the tenants and paying
the mortgage, he was also doing the leasing and he excluded
Thomas by changing the locks on the building.

Count 13: Much of the evidence that establishes Farrell’s
guilt under Counts 1 and 3 also proves he knowingly or
intentionally possessed with intent to distribute the 15 grams
of crack cocaine found in apartment #4 of the Rosedale
building – or at least aided and abetted that possession, for
which he would be liable as a principal. See 21 U.S.C.
§ 841(a)(1), (b)(1)(B)(iii); 18 U.S.C. § 2.

Count 14: The Government was required to prove Farrell
knowingly or intentionally distributed powder cocaine. See
21 U.S.C. § 841(a)(1), (b)(1)(C). On November 25, 2003,
Mason, who was cooperating with FBI agents, met Law
outside Law’s aunt’s house, where he gave Law $3,500 in
marked bills for 125 grams of powder cocaine. Law did not,
however, give Mason the cocaine at that time; rather, they
agreed Law would give Mason the drugs later that day at the
Shiloh Baptist Church. Farrell entered the church some 20 to
30 minutes after Law had done. Five to ten minutes later,
Farrell and Law exited the church together and got into
Farrell’s van. After Mason arrived, Law left Farrell’s van
carrying a brown paper bag containing powder cocaine,
 17
which he gave to Mason in Mason’s car. That night, a
Metropolitan Police officer conducting a traffic stop of Farrell
seized $3,411, of which $3,030 was in marked bills the FBI
had provided to Mason earlier that day for the controlled
purchase from Law.

Count 15: As with Count 14, the Government was
required to prove Farrell knowingly or intentionally
distributed powder cocaine to Valentine-Bey. On November
26, 2003, at the direction of FBI agents, Valentine-Bey
bought 250 grams of powder cocaine from Farrell outside the
Shiloh Baptist Church.

Farrell argues the admission of the IRS records showing
he had failed to file tax returns for several years was
nonetheless prejudicial because the records “bolstered the
credibility of the cooperating witnesses whose testimony was
the core of the government’s proof of the narcotics
conspiracy.” Farrell’s theory appears to be that, insofar as the
cooperating witnesses testified about Farrell’s drug activities,
their testimony was bolstered by the inference Farrell fears
the jury drew from the IRS records, namely, that Farrell was
dishonest and therefore the type of person who would deal
drugs as charged. Farrell advances no reason, however, to
doubt the credibility of the cooperating witnesses upon whose
testimony the Government built its case against him, and so
his objection founders; an error that bolsters the credibility of
a witness is harmless unless that witness’s testimony is
“otherwise[ ]suspect.” United States v. Cunningham, 145
F.3d 1385, 1394 (D.C. Cir. 1998); see also United States v.
Lampkin, 159 F.3d 607, 613 (D.C. Cir. 1998) (error not
harmless where witness’s credibility “was very much in doubt
throughout the trial”).

Farrell’s co-defendant Law, however, has questioned the
credibility of one of those witnesses, namely, Mason. As
 18
described above, Mason testified about his transactions with
Law and about Law’s relationship with Farrell. Attempting to
undermine Mason’s credibility, Law argues that “Mason
made many vague and contradictory statements concerning
the quantity of drugs he allegedly bought from Mr. Law”; that
there was evidence contradicting Mason’s testimony about
where the transactions between Mason and Law occurred; and
that Mason’s testimony was motivated by his plea bargain,
under which he would gain leniency from prosecutors for his
own actions. The connection between Mason’s testimony and
any general inference of Farrell’s bad character that the jury
might have drawn from the IRS records is so attenuated that
the IRS records could not have bolstered Mason’s credibility,
let alone affected the jury’s decision with respect to Farrell.
We conclude the admission of the IRS records was, if
erroneous, harmless with respect to the drug-related charges.

C. The Binder Tabs

At trial, the Government played recordings of numerous
phone calls between Farrell and others. To assist the jury in
following those recordings, the Government provided tabbed
binders of transcripts of the recordings. The Government
contended ten of those recorded conversations were between
Farrell and drug sources in New York, which in turn showed
he had a leadership role in the conspiracy. Although the
transcripts of those ten conversations were labeled as being
between Farrell and an “Unknown Male,” the Government
placed seven of them behind a tab labeled “Farrell & NY
Source #1” and the other three behind a tab labeled “Farrell &
NY Source #2.” Farrell disputed the Government’s
contention that he was speaking with drug sources in those
conversations; the participants had not identified themselves
in the recordings, and no witness at trial identified the people
with whom Farrell was speaking. The jury nonetheless
agreed with the Government, which resulted in the
 19
enhancement of Farrell’s sentences by virtue of his leadership
role in the conspiracy. See U.S.S.G. § 3B1.1(a). Farrell
contends the district court, pursuant to Federal Rule of
Evidence 403, should have refused to let the Government use
the tabs because their usefulness “was substantially
outweighed by unfair prejudice.” A “more neutral label, such
as ‘Farrell & Unknown Male,’” he argues, “would have just
as effectively assisted the jury in turning to the appropriate
section within the binder.” We hold the district court did not
abuse its discretion.

“The principal risk of indiscriminately permitting the use
of transcripts by jurors is that ... the jurors may ... transform
the transcript into independent evidence of the recorded
statements.” United States v. Holton, 116 F.3d 1536, 1540
(D.C. Cir. 1997). A district court, however, has discretion to
permit the use of a transcript “for the limited purpose of being
used as a jury aid [to] help prevent jury confusion and wasted
time as a tape is being played,” provided the court uses
“procedures ... to ensure that the jury does not rely on one
party’s version of the transcript instead of the tape recording.”
Id. at 1541-43 (quotation marks omitted); see also United
States v. Slade, 627 F.2d 293, 302-04 (D.C. Cir. 1980). In
Holton, we prescribed certain precautionary procedures,
including instructing the jurors “the tape recording constitutes
evidence of the recorded conversations and the transcript is an
interpretation of the tape,” “they should disregard anything in
the transcript that they do not hear on the recording itself,”
and if only one party submits a transcript, then “the jury must
be informed that the transcript is only one party’s version.”
116 F.3d at 1542-43. Depending upon the circumstances, we
pointed out, additional procedures may be necessary. See id.
at 1543.

It is undisputed that the district court gave the requisite
Holton instructions. Farrell claims the instructions were
 20
nonetheless inadequate because they addressed only the
“transcripts.” The tabs, Farrell says, “were not part of the
transcript, but were extraneous to the transcript.” In order to
agree with Farrell, we would have to conclude the district
court was required to find that, in the absence of an
instruction specifically addressing the tabs, the jury would
believe it could consider the tabs as evidence. In light of the
instructions the district court gave, we conclude the district
court need not have attributed such a peculiar belief to the
jury.

First, the tabs were obviously part of the Government’s
presentation and organization of the transcripts. More
important, the clear import of the district court’s instructions
was that only the tapes were to be considered as evidence of
the recorded conversations. When the binders were first
presented to the jury, the court explained:

The evidence in this case is what you hear on the tape
recordings, not what is printed on these transcript pages.
These transcript pages have been prepared and provided
to you solely for whatever assistance they may be to you
in identifying the speaker[s] who are speaking or the
words that are spoken.

Similarly, after the close of the evidence, the district
court instructed the jury: “Transcripts of these tape recorded
conversations have been shown to you solely for your
convenience ... in identifying the speakers as the[] recordings
were being played. ... What you hear on the tape[s]
themselves is evidence in the case.” Although it might have
been prudent for the district court to expand the Holton
instructions expressly to reach the binders and tabs, we will
not require district courts to presume the jury lacks common
sense. We therefore reject Farrell’s challenge to the use of
the binder tabs.
 21
D. The Reasonableness of the Sentences

Farrell was sentenced to concurrent terms of 324 months
imprisonment for each offense relating to a quantity of drugs,
namely, Counts 1 and 13-15. He contends these sentences
were unreasonable because the district court “failed to take
into account the increasing[ly] prevalent view that sentences
based upon the crack cocaine Sentencing Guidelines were
improperly harsh when compared to those issued for
involvement with powder cocaine.”

“[W]e ... review any sentence, whether within the
[Sentencing] Guidelines range or not, to ensure that it is
reasonable in light of the sentencing factors that Congress
specified in 18 U.S.C. § 3553(a).” United States v. Dorcely,
454 F.3d 366, 374 (D.C. Cir. 2006) (quotation marks
omitted).5 A “sentence within a properly calculated
Guidelines range is entitled to a rebuttable presumption of
reasonableness.” Dorcely, 454 F.3d at 376; see Rita v. United
States, 127 S. Ct. 2456, 2462 (2007).

We reject Farrell’s contention because, contrary to his
assertion, the district court, when considering the factors
enumerated in § 3553(a), clearly took account of the
Guidelines’ disparate treatment of sentences for crack and for

5
Section 3553(a) “tells the sentencing judge to consider (1)
offense and offender characteristics; (2) the need for a sentence to
reflect the basic aims of sentencing, namely (a) ‘just punishment’
(retribution), (b) deterrence, (c) incapacitation, (d) rehabilitation;
(3) the sentences legally available; (4) the Sentencing Guidelines;
(5) Sentencing Commission policy statements; (6) the need to avoid
unwarranted disparities; and (7) the need for restitution. The
provision also tells the sentencing judge to ‘impose a sentence
sufficient, but not greater than necessary, to comply with’ the basic
aims of sentencing as set out above.” Rita v. United States, 127 S.
Ct. 2456, 2463 (2007).
 22
powder cocaine offenses. Indeed, the district court calculated
the sentencing range as though Farrell’s offenses involved
powder rather than crack cocaine. The resulting sentencing
range was 262-327 months imprisonment, rather than 360
months to life imprisonment. After noting that Farrell’s
crimes were not “victimless,” that he was “quite along in
age,” and that his health was declining, the district court
settled upon concurrent sentences of 324 months
imprisonment for each of Counts 1 and 13-15, which was
well below the Guidelines range for crack cocaine, but within
(albeit near the high end of) the Guidelines range when crack
cocaine is treated as powder cocaine. Thus the district court
accounted for the relative harshness of sentences for crack
cocaine offenses under the Guidelines; indeed, the court
eliminated the disparity altogether.

Though Farrell’s arguments for re-sentencing focus
almost exclusively upon the Guidelines’ disparate treatment
of crack and of powder cocaine offenses, he throws the court
a curveball at the end of his brief. In May 2007, the
Commission amended the Guidelines to lower by two the
base offense level for certain crack cocaine offenses, which
would reduce but not eliminate the disparity. See Sentencing
Guidelines for United States Courts, 72 Fed. Reg. 28,558,
28,571-73 (2007); Nat’l Fed. Defender Sentencing Res.
Counsel, Applying the Crack Amendments 101 (Nov. 1,
2007), available at http://www.fd.org/pdf_lib/crack.pdf.6
Farrell asserts these amendments “are indicative of a shift

6
The amended Guidelines took effect on November 1, 2007.
Sentencing Guidelines for United States Courts, 72 Fed. Reg. at
28,558. The Commission subsequently voted to give retroactive
effect to the amendments, effective March 3, 2008. Sentencing
Guidelines for United States Courts, 73 Fed. Reg. 217, 217, 220
(Jan. 2, 2008). We express no view as to what effect, if any, these
amendments have upon Farrell’s sentences.
 23
away from the draconian penalties for those involved with
cocaine, be it of a powder or crack variety.” (Emphasis
added.) But it does not follow from this recent effort to
reduce the disparity between the sentences for crack and for
powder cocaine offenses that the Commission is troubled by
the sentences for powder cocaine offenses. Obviously, one
can eliminate the disparity without altering the sentences for
powder cocaine offenses, as the district court did here.

Finding Farrell’s arguments without merit, we conclude
his below-Guidelines sentences were reasonable.

III. Nathaniel Law

Law argues the district court erred by denying his motion
to suppress without holding an evidentiary hearing or
allowing him to be present. We reject this challenge because
the district court properly decided the motion as a question of
law. Law claims the district court improperly denied his
request for an entrapment instruction. We deny this claim
because Law offered no evidence of inducement. Law also
argues his life sentence was unlawful because (1) the district
court improperly aggregated the amount of drugs involved in
the conspiracy; (2) the government presented insufficient
evidence of Law’s involvement in a conspiracy that sold each
drug quantity; and (3) his prior crimes were not felony drug
offenses. We reject all three arguments because the district
court rightly aggregated the drug amounts, the evidence was
more than sufficient, and Law waived his argument that his
prior crimes were not felony drug offenses. The government
concedes that Law’s conviction for selling crack cocaine,
Count 11, merges with his conviction for selling the same
drugs near a school, Count 12. Accordingly, we reverse that
conviction and remand for re-sentencing. Finally, like
Farrell, Law joins both of Fletcher’s challenges to the
 24
Government’s expert opinion testimony, which, as discussed
in Part IV, we reject.

A. The Motion to Suppress

After executing a search warrant on Law’s apartment
(apartment #3) in the Rosedale building, FBI agents
discovered a key seized from Law during his prior arrest fit
the lock of the adjacent unit (apartment #4). Since the
warrant did not authorize the search of this apartment, they
asked landlord Thomas for permission to do so. She said the
apartment was “currently vacant and [was] being used to store
some furniture and other matters” and Law “might have a set
of keys to Apartment #4, but could not provide details
concerning why.” After further discussion, she consented to
the search of apartment #4. Inside, agents found drugs and
other incriminating evidence. The district court rejected
Law’s motion to suppress this evidence without holding an
evidentiary hearing or allowing him to be present.7

Law argues this was error. A defendant is entitled to an
evidentiary hearing on his motion to suppress “only upon
factual allegations which, if established, would warrant
relief.” United States v. Thornton, 454 F.2d 957, 967 n.65
(D.C. Cir. 1971). Under the Due Process Clause, a
“defendant is guaranteed the right to be present at any stage
of the criminal proceeding that is critical to its outcome if his
presence would contribute to the fairness of the procedure,”
and this can include a suppression hearing. Kentucky v.
Stincer, 482 U.S. 730, 745 (1987); see United States v.
Hodge, 19 F.3d 51, 52-53 (D.C. Cir. 1994). Nevertheless, a
defendant’s presence is not required if the court can decide
the suppression motion as a matter of law. See Valdez v.

7
At the time, Law was in another state undergoing a
competency evaluation.
 25
Gunter, 988 F.2d 91, 93-94 (10th Cir. 1993). Accordingly,
the viability of both of Law’s claims – the right to an
evidentiary hearing and right to be present – turns on whether
the district court needed to resolve any disputes of material
fact to decide Law’s suppression motion.

Law argues the search of apartment #4 violated the
Fourth Amendment because the agents had no search warrant.
The district court concluded Thomas had authority to consent
to the search and, even if she did not, the FBI agents
reasonably believed she did. The second theory suffices for
our purposes. “[C]onsent of one who possesses common
authority over premises or effects is valid as against the
absent, nonconsenting person with whom that authority is
shared.” United States v. Matlock, 415 U.S. 164, 170 (1974).
While a landlord cannot ordinarily consent to a search of a
tenant’s home, see Chapman v. United States, 365 U.S. 610,
616-17 (1961), she can consent to a search of an unleased
apartment, see United States v. Kelly, 551 F.2d 760, 764 (8th
Cir. 1977). Even if a landlord does not have authority to
consent to a search, agents may rely upon her assurance that
she has such authority, if objective circumstances make
reliance reasonable. See Illinois v. Rodriguez, 497 U.S. 177,
188 (1990). Whether that reliance was reasonable is a
question of law. United States v. James, 353 F.3d 606, 615
(8th Cir. 2003). Thus the question for us is whether, under
Law’s version of events, the FBI agents reasonably relied
upon Thomas’s representation that apartment #4 was
unleased.

According to Law’s motion to suppress, Thomas told the
agents apartment #4 was “currently vacant and [was] being
used to store some furniture and other matters” and that Law
“might have a set of keys.” Under these circumstances, the
agents reasonably relied on Thomas’s representation that she
had authority to consent to a search of the apartment. After
 26
all, Thomas told them the apartment was “currently vacant,”
which is the equivalent of being unleased, see WEBSTER’S
THIRD NEW INTERNATIONAL DICTIONARY 2527 (1981)
(“vacant” means “not filled or occupied by an incumbent,
possessor, or officer”), and landlords have authority to
consent to searches of unleased units, see Kelly, 551 F.2d at
764. It was reasonable for the agents to believe Thomas knew
the occupancy status of one of only four apartment units in
her building. Admittedly, Thomas’s inability to explain why
Law had keys to the apartment makes this a closer case; but
this fact, taken by itself, was not sufficient to undermine her
credibility. Law points to United States v. Whitfield, 939 F.2d
1071 (D.C. Cir. 1991), where this court held the police did
not reasonably rely on a mother’s consent to search the room
of her 29-year-old son. But the present case is far different
because Thomas told the agents no one lived in the apartment.
In sum, the district court did not err by refusing to hold an
evidentiary hearing and by denying Law an opportunity to be
present.8

B. The Entrapment Instruction

Law argues the district court improperly denied his
request for an entrapment instruction. He was entitled to this
instruction if there was “sufficient evidence from which a
reasonable jury could find entrapment.” United States v.
Glover, 153 F.3d 749, 754 (D.C. Cir. 1998) (alterations
omitted). We review the district court’s decision not to give
the instruction de novo, viewing the facts in the light most
favorable to Law. Id. at 752.

8
We decline to address whether Federal Rule of Criminal
Procedure 43 ever applies to a suppression hearing, because that
rule does not require a defendant be present at a “hearing on a
question of law,” as was the case here. FED. R. CRIM. P. 43(b)(3).
 27
The entrapment defense protects an “otherwise law-
abiding citizen who, if left to his own devices, likely would
have never run afoul of the law.” Jacobson v. United States,
503 U.S. 540, 553-54 (1992). This defense “has two related
elements: government inducement of the crime, and a lack of
predisposition on the part of the defendant to engage in the
criminal conduct.” Glover, 153 F.3d at 754. If the defendant
meets the initial burden of proving government inducement,
the government can rebut by demonstrating he was
nevertheless predisposed to commit the crime. When a
government informant buys drugs from a defendant, the
defendant can show inducement by pointing to “evidence of
reluctance” to sell the drugs or the informant’s use of
“persuasive overtures,” beyond those “ordinarily present in a
drug transaction.” Id. While a government agent’s appeal to
friendship could, under some circumstances, be a “persuasive
overture,” we have never found such a plea “sufficiently
strong” to satisfy this requirement. See United States v.
Evans, 216 F.3d 80, 90 (D.C. Cir. 2000).

Nor is this the case to do so. Law sold powder cocaine to
his friend Mason after Mason had become a government
informant. Yet, Law had never been reluctant to sell drugs to
Mason, as he had sold him powder cocaine for several years
before Mason ever became an informant. Moreover, while
Law and Mason were longtime friends, Mason denied using
this friendship to get Law to sell him drugs and Law
presented no evidence to the contrary. There is similarly no
evidence to support Law’s claim that Mason used the threat of
force to induce the drug sale. Law also sold crack cocaine to
Atcherson and an unnamed informant, but Law points to no
evidence he was reluctant to make this sale; and, he offers no
evidence that either Atcherson or the unnamed informant
appealed to Law’s friendship. Moreover, any negative
inference that one could draw from the government’s failure
to tape-record Law’s transactions with Mason and Atcherson
 28
cannot make up for Law’s failure to present any evidence of
entrapment. In sum, Law failed to introduce sufficient
evidence to meet his initial burden of showing government
inducement.

C. The Mandatory Life Sentence

21 U.S.C. § 841(a)(1) makes it unlawful for anyone
“knowingly or intentionally ... to manufacture, distribute, or
dispense, or possess with intent to manufacture, distribute, or
dispense, a controlled substance.” A defendant convicted of
violating § 841(a) “shall be sentenced to a mandatory term of
life imprisonment without release” if the violation involved
either 50 grams or more of crack cocaine or 5 kilograms or
more of cocaine powder, and the offender has two or more
prior convictions for “felony drug offense[s].” The jury
convicted Law, under 21 U.S.C. § 846, of conspiring, in
violation of these provisions of § 841, to distribute 50 grams
or more of crack cocaine (more precisely, of 150 grams or
more), 5 kilograms or more of powder cocaine, and 100
grams or more of heroin, and the government showed he had
been convicted of three prior felony drug offenses.
Accordingly, the district court imposed a mandatory life
sentence. Law argues we should overturn this sentence
because: (1) the district court improperly aggregated the
amount of drugs involved in the conspiracy; (2) the
government presented insufficient evidence of Law’s
involvement in a conspiracy that sold each drug quantity; and
(3) his prior crimes were not felony drug offenses. We reject
the first two challenges and find Law waived the third.

1. The aggregation of drug amounts

A defendant convicted of conspiring to deal drugs in
violation of § 846 “shall be subject to the same penalties as
those prescribed for the offense” in § 841(a). 21 U.S.C.
 29
§ 846. Law claims this means the district court can sentence
a defendant convicted of conspiracy under § 846 only for the
largest “offense” (violation of § 841(a)) within that
conspiracy. Thus, if a conspiracy involves five sales of 10
grams of crack cocaine, the district court can only sentence
the defendant like someone who sold 10 grams of crack
cocaine, not like someone who sold 50 grams. Law argues
the district court erred by allowing the jury to aggregate the
drug quantities throughout the conspiracy, and then by relying
on this figure to impose the mandatory life sentence. Since
Law never raised this argument before the district court, we
review for plain error. See United States v. Coles, 403 F.3d
764, 767 (D.C. Cir. 2005).

We join our sister circuits in holding a defendant
convicted of conspiracy to deal drugs, in violation of § 846,
must be sentenced, under § 841(b), for the quantity of drugs
the jury attributes to him as a reasonably foreseeable part of
the conspiracy. See United States v. Pressley, 469 F.3d 63,
65-67 (2d Cir. 2006) (per curiam); United States v. Gori, 324
F.3d 234, 237 (3d Cir. 2003); United States v. Pruitt, 156
F.3d 638, 644-45 (6th Cir. 1998). As the Supreme Court has
explained, a “single agreement to commit several crimes
constitutes one conspiracy.” United States v. Broce, 488 U.S.
563, 570-71 (1989). As a result, a single violation of the
conspiracy statute encompasses all of the crimes reasonably
foreseeable within that conspiracy. See United States v.
Walker, 160 F.3d 1078, 1093 (6th Cir. 1998) (a “conspiracy is
a single violation of the drug laws, and the fact that this
particular conspiracy was characterized by separate
transactions is a fact of no legal significance”). Here, the
conspiracy was dealing drugs, and thus the entire sum of the
drugs within the conspiracy constituted a single conspiracy
violation. Accordingly, the district court did not commit
 30
plain error by relying on the jury’s aggregated drug quantity
determination in imposing the life sentence on Law.9

2. The sufficiency of the evidence

Law argues that even if the jury could aggregate the drug
sales, the government did not present sufficient evidence that
he took part in a conspiracy involving the alleged quantity of
each of the three drug types. In evaluating Law’s sufficiency
challenge, “[w]e review the sufficiency of the evidence de
novo, considering it in the light most favorable to the
government, to determine whether any rational trier of fact
could have found [Law] guilty beyond a reasonable doubt of
all the required elements of the crime.” Valdes, 475 F.3d at
1322.

We find the government presented ample evidence that
Law took part in a conspiracy involving at least 50 grams of
crack cocaine, 5 kilograms of powder cocaine, and 100 grams
of heroin. “The drug conspiracy statute, 21 U.S.C. § 846,
dispenses with the usual requirement of an overt act and
requires only an agreement to commit” a violation of
§ 841(a). United States v. Baugham, 449 F.3d 167, 171 (D.C.
Cir. 2006). Farrell supplied Law with drugs to sell, and both
Fletcher and Farrell accompanied him during drug sales.
Moreover, Law lived in the Rosedale building, which was a
distribution center for the conspiracy. Inside of his apartment
and the adjacent apartment #4, police found drugs, drug
paraphernalia, and business cards for Farrell and Fletcher.

9
Law’s related Sixth Amendment claims that (1) his trial
counsel was ineffective for failing to raise the aggregation
argument, and (2) the jury did not find he conspired to sell a
sufficient quantity of each drug type in a single transaction, fail for
the same reason.
 31
This is more than enough to show Law agreed to distribute
drugs with Farrell and Fletcher.

In addition, the government presented overwhelming
evidence as to the drug quantities in the conspiracy. We
discuss only the sales in which Law personally participated,
as those are sufficient to sustain his conviction:

At least 50 grams of crack cocaine: Cyrus testified Law
sold him 62 grams of “cocaine,” when Fletcher, Cyrus’s
regular supplier, went out of town. Law points out Cyrus
only testified he bought “cocaine” from Law, not specifically
crack cocaine. However, Cyrus testified: (1) he bought crack
cocaine from Fletcher approximately 45 times, and over half
those purchases were of 62 grams; (2) he bought powder
cocaine from Fletcher only one time; (3) he paid Fletcher
$2000 for 62 grams of crack cocaine; and (4) he paid Law
$2000 for 62 grams of “cocaine” on the day in question. The
jury could have concluded the “cocaine” Cyrus was referring
to was crack – after all, that is what Cyrus almost always
bought from Fletcher, at the same price.10 If this is not
enough, Law sometimes accompanied Fletcher when he made
crack sales to Cyrus – involvement sufficient to give Law
reasonable knowledge that the conspiracy sold far more than
50 grams of crack cocaine. In addition, Law sold Atcherson a
total of 181.9 grams of crack cocaine over 6 transactions.
The jury could reasonably have concluded at least some of
these sales were part of the conspiracy. For example, Fletcher
was near the scene for one sale and Law entered Fletcher’s
minivan during this transaction.

10
There is also nothing to Law’s argument that this deal was
not in furtherance of the conspiracy, as the jury had ample evidence
to conclude Law was simply taking on his co-conspirator’s role.
 32
At least 5 kilograms of powder cocaine: Mason testified
Law sold him between 125 and 250 grams of powder cocaine
at least once a week between September 2000 and February
2003, which would total at least 13 kilograms. At another
point, he testified he bought powder cocaine at least 20 to 30
times from Law and added that he bought “at least” 9
kilograms in total. Law challenges Mason’s credibility
because of this inconsistency and because Mason claimed
some of the drug buys took place at the Center, even though it
had been padlocked by 2001. However, Mason never
claimed he bought cocaine at the Center after it closed.
Moreover, this is merely an argument about credibility and
we give “full play to the right of the jury to determine
credibility.” United States v. Foster, 783 F.2d 1087, 1088
(D.C. Cir. 1986). Finally, there is little doubt these sales were
part of the conspiracy, as Mason testified Law told him his
source was “brother,” which was Farrell’s nickname.

At least 100 grams of heroin: Mason testified Law sold
him 250 grams of heroin, which Farrell supplied.11

3. The felony drug offenses

Law claims the district court improperly imposed a life
sentence under § 841(b) because his three prior convictions
were not “felony drug offenses.” We conclude Law has
waived this objection by failing to raise it to the district court.

11
In a footnote in his opening brief, Law suggests the
insufficiency of the evidence was exacerbated by the prosecutor
making prejudicial comments during closing argument. While we
see nothing wrong with the prosecutor’s comments, we treat Law’s
argument as waived because he failed to develop it. See
Democratic Cent. Comm. of D.C. v. Wash. Metro. Area Transit
Comm’n, 485 F.2d 786, 790 n. 16 (D.C. Cir. 1973).
 33
21 U.S.C. § 851 establishes the procedural framework for
deciding whether a defendant had been convicted of a prior
felony offense. Under § 851(a), the government must file “an
information” identifying the prior conviction. Under
§ 851(b), the district court must then tell the defendant he has
to “affirm[] or den[y] that he has been previously convicted as
alleged in the information,” and that “any challenge to a prior
conviction which is not made before sentence is imposed may
not thereafter be raised to attack the sentence.” § 851(b)
(emphasis added). The defendant must then respond, in
writing, under § 851(c), which explains, in pertinent part,
“[a]ny challenge to a prior conviction, not raised by response
to the information before an increased sentence is imposed in
reliance thereon, shall be waived unless good cause be shown
for failure to make a timely challenge.” § 851(c)(2)
(emphasis added). Here, the government alleged Law had
been convicted of three prior felony drug offenses and Law
did not dispute this claim.

Without citing any authority, Law argues the phrase “any
challenge to a prior conviction” in subsections (b) and (c)(2)
refers only to a collateral challenge to a prior conviction, not
to arguments that the prior conviction was not a felony
offense. The text of § 851 and its carefully defined
framework doom his argument. As explained above, the
government must first allege all aspects of a prior conviction,
including felony offense status; the court must then tell the
defendant he has to raise “any challenge”; and, finally, the
defendant must bring “any challenge” or waive the argument.
It strains credulity to argue “any challenge” refers only to
collateral attacks on the prior conviction, as opposed to any
challenges whatsoever to the government’s claims as to the
conviction, including allegations about offense status. See
United States v. Brooks, 508 F.3d 1205, 1208-09 (9th Cir.
2007) (strongly suggesting the § 851 waiver applies to
challenges to “the validity or nature of [the defendant’s]
 34
conviction”) (emphasis added). Indeed, courts have regularly
held the § 851 waiver applies to arguments that the prior
conviction has not become final, even though these are not
collateral challenges. See, e.g., United States v. VanDoren,
182 F.3d 1077, 1083 (9th Cir. 1999); United States v. French,
974 F.2d 687, 696-97 (6th Cir. 1992) (as amended).

In this case, the government filed papers, under § 851(a),
showing Law had been convicted of three felony drug
offenses. The district court then informed Law, as required
by § 851(b), that he would waive any challenge he did not
raise now. Law did not bring “any challenge” under § 851(c).
Accordingly, since Law did not argue his crimes were not
felony drug offenses before the district court, and has not
shown good cause for failing to do so, he may not now raise
them “to attack the sentence.” § 851(b).12

D. Other Sentencing Issues

The government concedes Law’s conviction for selling
crack cocaine to Atcherson, Count 11, merges with his
conviction for selling the same drugs near a school, Count 12.

12
In arguing his prior crimes were not “felony drug offenses,”
Law relies upon United States v. West, 393 F.3d 1302, 1305 (D.C.
2005), which held a crime is a “felony drug offense” only if it is
both punishable by more than one year in prison and characterized
as a felony by the punishing jurisdiction. However, after oral
argument in this case, the Supreme Court decided Burgess v.
United States, 128 S. Ct. 1572 (2008), which rejected the approach
in West and held a “felony drug offense” is any offense
“‘punishable by imprisonment for more than one year under any
law of the United States or of a State or foreign country,’”
regardless of how the punishing jurisdiction classifies it. Id. at
1573 (quoting 21 U.S.C. § 802(44)). Since all of Law’s prior
convictions were punishable by more than one year in prison, he
would not have prevailed even if he did not waive this argument.
 35
Conviction on both counts violates the Double Jeopardy
Clause and we vacate the distribution conviction on Count 11
and remand for re-sentencing. See United States v. Baylor, 97
F.3d 542, 548 (D.C. Cir. 1996). During re-sentencing, the
district court should address the inconsistency between Law’s
Judgment and Commitment Order, which states he was
convicted for “distribution” on Count 13, and the indictment
and jury verdict, which charge and find him guilty of
“possession with intent to distribute.”

IV. Carroll Fletcher

We now turn to Carroll Fletcher’s claims. First, Fletcher
argues that the evidence was insufficient for a jury to convict
him of Count 4, maintaining a drug residence at 200 K St.
N.W. The Government concedes on appeal that the evidence
is in fact insufficient; accordingly, we reverse Fletcher’s
conviction on that count and remand for re-sentencing.
Second, Fletcher challenges his mandatory life sentences for
his convictions on Counts 1 and 5. A life sentence is
mandatory for certain drug offenders convicted under 21
U.S.C. § 841(b)(1)(A)(iii) and § 846 who have two prior
felony drug convictions. Here, the Government relied on
Fletcher’s 1977 and 1987 drug convictions as the two prior
felony drug convictions. Fletcher argues that (1) the 1977
conviction was “set aside” under the Federal Youth
Corrections Act (FYCA) and (2) the Government did not
sufficiently prove the conviction because it relied only on a
docket sheet entry. Even assuming his 1977 conviction was
set aside under the FYCA, however, the conviction still
counts for purposes of sentencing under § 841(b). We need
not decide at this stage whether the Government adequately
proved the 1977 conviction: We are already remanding
Fletcher’s convictions for re-sentencing because we are
reversing his drug-residence conviction; and on remand, the
Government plans to provide additional proof of Fletcher’s
 36
1977 conviction. Third, Fletcher and his co-defendants
Farrell and Law raise a Confrontation Clause challenge to
expert witness testimony by a police detective; that argument
is inconsistent with our precedents. Fourth, Fletcher, Farrell,
and Law contend that the Government’s expert forensic
scientist gave improper expert testimony; we reject that claim.

A. Maintaining a Drug Residence

The jury found Fletcher guilty of Count 4, maintaining a
drug residence at 200 K Street in violation of 21 U.S.C.
§ 856(a)(1). Section 856(a)(1) makes it unlawful to
“knowingly open, lease, rent, use, or maintain any place,
whether permanently or temporarily, for the purpose of
manufacturing, distributing, or using any controlled
substance.” See United States v. Lancaster, 968 F.2d 1250,
1254 (D.C. Cir. 1992). On appeal, Fletcher argues that the
evidence shows that another person rented and maintained the
200 K Street apartment; Fletcher further contends that there
was no evidence that he owned, leased, lived in, had a key to,
or had any control over the apartment; the evidence showed
only that he went there occasionally to carry out drug
transactions. The Government concedes on appeal that the
evidence is insufficient to support Fletcher’s conviction on
this count. Accordingly, we reverse Fletcher’s § 856(a)(1)
conviction; as the Government acknowledges, we must
therefore remand Fletcher’s case for re-sentencing.

B. The Mandatory Life Sentence

The jury found Fletcher guilty of, among other counts,
(1) conspiracy to possess with intent to distribute and
conspiracy to distribute five kilograms or more of cocaine, 50
grams or more of cocaine base, and 100 grams or more of
heroin in violation of 21 U.S.C. §§ 841 and 846 (Count 1) and
of (2) distributing 50 grams or more of cocaine base in
 37
violation of § 841 (Count 5). For each of these counts, the
district court sentenced Fletcher to life imprisonment without
release – a mandatory sentence for offenders such as Fletcher
who were convicted under those provisions “after two or
more prior convictions for a felony drug offense have become
final.” § 841(b)(1)(A); see also § 846 (“Any person who
attempts or conspires to commit any offense defined in this
subchapter shall be subject to the same penalties as those
prescribed for the offense, the commission of which was the
object of the attempt or conspiracy.”).

Fletcher had two prior felony drug convictions: a 1977
conviction for possession with intent to distribute a controlled
substance and a 1987 conviction for conspiracy to distribute a
controlled substance. He argues that the § 841 and § 846
mandatory life sentences do not apply to him, however,
because (1) the 1977 conviction was later “set aside” under
§ 5021 of the Federal Youth Corrections Act, and (2) the
Government did not prove his 1977 conviction sufficiently.
See Federal Youth Corrections Act, 18 U.S.C. § 5005 et seq.,
(1976), repealed by Comprehensive Crime Control Act of
1984, Pub. L. No. 98-473, § 218(a)(8), 98 Stat. 1976, 2027.

Even if we assume Fletcher’s 1977 conviction was set
aside under the Federal Youth Corrections Act – a question
we need not decide – the district court still must take it into
account in determining his sentence under § 841(b). The term
“set aside” and the related term “expunge” have unfortunately
not acquired settled meanings. Compare U.S.S.G. § 4A1.2,
cmt. n.10 (conviction removed from criminal record “for
reasons unrelated to innocence or errors of law” such as a
conviction removed from criminal record to serve a social
policy goal, for example “to restore civil rights or to remove
the stigma associated with a criminal conviction,” is “set
aside”), with Dickerson v. New Banner Inst., Inc., 460 U.S.
103, 115 (1983) (under Iowa law, “expunction does not alter
 38
the legality of the previous conviction and does not signify
that the defendant was innocent of the crime to which he
pleaded guilty”). The FYCA uses the term “set aside” in the
same way the Sentencing Commission does – to designate a
conviction removed from a criminal record for policy reasons
unrelated to innocence or legal error, namely, “to promote the
rehabilitation of youth offenders.” Tuten v. United States,
460 U.S. 660, 663-65 (1983). If expungement or set-aside of
a conviction is designed to allow an individual to make a
fresh start, then if the individual commits a later crime, he or
she may forfeit the benefits of the expungement for purposes
of recidivist sentencing provisions, at least unless Congress
provides otherwise. For as we have recognized, “[s]ociety’s
stronger interest is in punishing appropriately an unrepentant
criminal.” United States v. McDonald, 991 F.2d 866, 872
(D.C. Cir. 1993).

Consistent with that principle, some federal recidivist
provisions expressly exempt expunged or set-aside
convictions. For example, the federal Sentencing Guidelines
do not count “expunged” convictions for a defendant’s
criminal history, although the Guidelines do count set-aside
convictions. See U.S. SENTENCING GUIDELINES MANUAL
§ 4A1.2(j) (2007); see also United States v. Fosher, 124 F.3d
52, 58 (1st Cir. 1997); Gass v. United States, 109 F.3d 677,
679-80 (11th Cir. 1997); United States v. Nicolace, 90 F.3d
255, 258 (8th Cir. 1996); United States v. Wacker, 72 F.3d
1453, 1479 (10th Cir. 1995); United States v. Levi, 45 F.3d
453, 457 (D.C. Cir. 1995) (conviction set aside under FYCA
was “properly included in determining [defendant’s]
sentence”); United States v. Ashburn, 20 F.3d 1336, 1343 (5th
Cir. 1994); United States v. McDonald, 991 F.2d at 871-72;
but see United States v. Kammerdiener, 945 F.2d 300, 301
(9th Cir. 1991).
 39
For purposes of sentences imposed under § 841,
however, Congress has not exempted from the “prior
convictions” that must be counted those convictions removed
from a criminal record for policy reasons unrelated to
innocence or an error of law. The courts of appeals that have
considered this § 841 question therefore have counted prior
felony drug convictions even where those convictions had
been set aside, expunged, or otherwise removed from a
defendant’s record for such reasons. See, e.g., United States
v. Norbury, 492 F.3d 1012, 1015 (9th Cir. 2007); United
States v. Sampson, 385 F.3d 183, 194-95 (2d Cir. 2004);
United States v. Graham, 315 F.3d 777, 783 (7th Cir. 2003);
cf. United States v. Acosta, 287 F.3d 1034, 1037 (11th Cir.
2002); United States v. Cisneros, 112 F.3d 1272, 1281-82
(5th Cir. 1997); United States v. Meraz, 998 F.2d 182, 183-88
(3d Cir. 1993); United States v. Campbell, 980 F.2d 245, 251
(4th Cir. 1992). We agree with those courts of appeals and
reach the same result here.

We now turn to Fletcher’s argument that the 1977
conviction was not sufficiently proved. The Government
must prove the conviction beyond a reasonable doubt. See 21
U.S.C. § 851(c)(1). The Government relied on a docket-sheet
entry to prove the 1977 conviction, but Fletcher claims that
the docket sheet was insufficient because it lacks “the
necessary indicia of reliability.” See United States v. Price,
409 F.3d 436, 445 (D.C. Cir. 2005). We need not address that
contention. Because we are reversing Fletcher’s drug-
residence conviction, we are already remanding his case for
re-sentencing. And the Government has informed the court
that, on remand, it will submit a copy of the judgment and
order of commitment for Fletcher’s 1977 conviction,
presumably eliminating any argument about the fact of the
conviction. If on remand the Government adequately proves
Fletcher’s 1977 conviction by producing the judgment and
commitment order, the district court must continue to count
 40
the 1977 conviction in determining Fletcher’s sentences for
Counts 1 and 5.

C. The Expert Testimony of Detective Thomas

All three defendants contest the admission of Detective
Tyrone Thomas’s expert testimony about the typical
operations of narcotics dealers, arguing that it was testimonial
hearsay admitted in violation of the Sixth Amendment as
interpreted in Crawford v. Washington, 541 U.S. 36 (2004).
Because the defendants did not object to Thomas’s testimony
at trial, we review the admission of the testimony only for
plain error. See FED. R. CRIM. P. 52(b); United States v.
Olano, 507 U.S. 725, 731-37 (1993). Defendants have shown
no error, much less plain error, because – as we have
previously held – Crawford does not limit the admissibility of
expert witness testimony.

In Crawford, the Supreme Court held that the
Confrontation Clause of the Sixth Amendment bars the
introduction of “testimonial” out-of-court statements by
witnesses who are not subject to cross-examination. See 541
U.S. at 68-69. The three defendants argue that Detective
Thomas formed his opinion about the typical operations of
narcotics dealers over the course of thousands of interviews,
and that his testimony is in reality the testimony of thousands
of out-of-court “witnesses” who were not subject to cross-
examination. But as this court has previously explained (in a
case involving this same expert), Crawford “did not involve
expert witness testimony and thus did not alter an expert
witness’s ability to rely on (without repeating to the jury)
otherwise inadmissible evidence in formulating his opinion
under Federal Rule of Evidence 703.” United States v.
Henry, 472 F.3d 910, 914 (D.C. Cir. 2007). Here, as in
Henry, Thomas testified based on his experience as a
narcotics investigator; he did not relate statements by out-of-
 41
court declarants to the jury. We therefore find that admission
of Thomas’s testimony was not error, much less plain error.

D. The Expert Testimony of Forensic Chemist Waninger

All three defendants contend that the district court erred
in denying a motion to strike the expert testimony of Eileen
Waninger, an FBI forensic chemist. Waninger testified that
evidence recovered from trash cans behind the Rosedale
building and from apartments # 3 and # 4 contained residue of
controlled substances, including cocaine base, cocaine
powder, and heroin. After allowing the prosecution to recall
Waninger so she could explain testing procedures in greater
detail, the district court denied the objection to her testimony.
We review the district court’s decision to admit the testimony
under an abuse-of-discretion standard. See Gen. Elec. Co. v.
Joiner, 522 U.S. 136, 146 (1997).

Defendants argue that the district court should have
barred Waninger’s testimony because the evidence “did not
establish that her conclusions ... were reliable.” Under
Daubert, the district court “must focus ‘solely on principles
and methodology, not on the conclusions that they generate.’”
Ambrosini v. Labarraque, 101 F.3d 129, 133 (D.C. Cir. 1996)
(quoting Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579,
595 (1993)). In acting as gatekeeper, the court “must
determine first whether the expert’s testimony is based on
‘scientific knowledge;’ and second, whether the testimony
‘will assist the trier of fact to understand or determine a fact
in issue.’” Id. (quoting Daubert, 509 U.S. at 592). As this
court noted in Ambrosini, the Daubert Court outlined four
factors that the district court could use to evaluate scientific
validity: “(1) whether the theory or technique can be and has
been tested; (2) whether the theory or technique has been
subjected to peer review and publication; (3) the method’s
known or potential rate of error; and (4) whether the theory or
 42
technique finds general acceptance in the relevant scientific
community.” Id. at 134. The court further emphasized that
the inquiry is a flexible one; the factors outlined are not
“necessarily applicable in every case or dispositive; nor are
[they] exhaustive.” Id.

Here, Waninger explained that, following FBI
Laboratory protocol of identifying residue “by more than one
technique,” she used at least two of the three following tests
to identify the residue on each item: (1) ion mobility
spectrometry, (2) infrared spectroscopy, and (3) gas
chromatography/mass spectrometry. She testified that ion
mobility spectrometry is an accepted “screening technique” in
forensic chemistry; that it has been used for “many, many
years”; that it is regularly used, including in Drug
Enforcement Agency narcotics testing and airport explosives
testing; and that a “lot of papers have been written” about its
use. She testified that infrared spectroscopy, a technique that
passes infrared light through a sample to determine its unique
chemical spectra, is used worldwide by forensic chemists to
detect controlled substances; that she has used it for ten years;
and that it has “been around a lot longer than that.” Finally,
Waninger testified about the third technique, gas
chromatography/mass spectrometry, which allows chemists to
“separate the components in a mixture and identify the
chemicals in them based upon their mass spectrum.” She
testified that the technique is “scientifically accepted,” that
she has used it for more than 15 years, and that it is widely
used by forensic chemists for the detection of controlled
substances. Waninger also explained that she represents the
FBI on a scientific working group for the analysis of seized
drugs, and that the group has published recommendations on
the minimum standards for qualitative identification of the
presence of a controlled substance using those techniques.
She further testified that her FBI laboratory followed those
standards.
 43
Waninger’s testimony that all three techniques have been
established for many years, are widely used, and are accepted
in the relevant scientific community is sufficient to satisfy the
“limited” Daubert inquiry. See Ambrosini, 101 F.3d at 134
(“General acceptance in the relevant scientific community
may be sufficient to permit the admissibility of expert
testimony ....”); see also United States v. Vitek Supply Corp.,
144 F.3d 476, 485-86 (7th Cir. 1998) (finding that techniques
including gas chromatography/mass spectrometry are “widely
used and generally accepted in the fields of analytical and
forensic chemistry”). We also note the expert’s personal
experience. See Kumho Tire Co. v. Carmichael, 526 U.S.
137, 148-49, 151-52 (1999). Waninger had worked at the
FBI’s Quantico lab for ten years, had previously worked as a
forensic scientist for a state police department for four years,
and had testified as a forensic chemistry expert at least 40
times “in federal and state courts throughout all of the United
States” as well as internationally. The district court did not
err in admitting her testimony.

V. Conclusion

For the reasons stated above, the judgments of the district
court are affirmed in part and reversed in part. The cases are
remanded to the district court for re-sentencing consistent
with this opinion.

So ordered.