                             In the

United States Court of Appeals
               For the Seventh Circuit

Nos. 12-2792 & 12-2793

U NITED STATES OF A MERICA,
                                                  Plaintiff-Appellee,
                                 v.

JAMA M IRE and H ASSAN R AFLE,
                                            Defendants-Appellants.


            Appeals from the United States District Court
     for the Southern District of Indiana, Indianapolis Division.
     No. 1:11-cr-00015-WTL-KPF—William T. Lawrence, Judge.


       A RGUED A PRIL 12, 2013—D ECIDED JULY 25, 2013




 Before B AUER, P OSNER, and F LAUM, Circuit Judges.
  B AUER, Circuit Judge. This case introduces a new
drug culture to the Seventh Circuit: the underground
world of “khat.”
  Jama Mire and Hassan Rafle became involved in a
conspiracy to distribute khat in the Indianapolis area.
Mire’s business, the Somali House of Coffee, served as a
place where people could get the “stuff” and enjoy it in
comfort. Government agents received a tip from a con-
2                                   Nos. 12-2792 & 12-2793

cerned Somali man about this khat-distribution con-
spiracy and launched an investigation into it. Mire and
Rafle were each indicted on one count of conspiracy
to possess with intent to distribute cathinone, in viola-
tion of 21 U.S.C. §§ 841(a) and 846. Mire was indicted
on two additional counts: (1) knowingly using or main-
taining a place for the purpose of distributing and using
cathinone, in violation of 21 U.S.C. § 856(a)(1); and
(2) possession with intent to distribute a mixture or
substance containing cathinone, in violation of 21 U.S.C.
§ 841(a). And after a bench trial, Mire and Rafle were
found guilty on all counts.
   The Defendants appeal their convictions; the sentences
they received are not at issue. Mire and Rafle contend,
first, that their due process rights were violated
because they were not given fair warning that the pos-
session of khat may be illegal; and second, that the
district court erred under Daubert in admitting govern-
ment expert witness testimony regarding khat plants
that were seized at the coffee house and tested for
cathinone, a controlled substance. Mire also contends
that his conviction for conspiracy to distribute khat and
his conviction for maintaining a place for the distribu-
tion or use of khat violate the Double Jeopardy Clause;
and anyway, that the evidence at trial was not sufficient
to support any of his convictions.
    Finding each of the arguments without merit, we affirm.
Nos. 12-2792 & 12-2793                                      3

                    I. BACKGROUND
    A. What is Khat?
  This is the first case involving khat to appear before this
Court, so we take the opportunity to explain it. Khat,1
pronounced “kY+t”—the common name for the plant
Catha Edulis—grows in parts of East Africa and the
Arabian Peninsula. It is known as the drug-of-choice
among Somali men who chew the leaves or mix them
in with tea for the stimulant effects. It is not smoked or
eaten in any fashion. The use of khat in Somalia is legal
and an accepted pastime, and the plant is readily sold in
the marketplace and stores. Estimates put its use among
Somali men as being equivalent to caffeine or tobacco
use among the American population. See Edward G.
Armstrong, Research Note: Crime, Chemicals, and Culture:
On the Complexity of Khat, 38 J. D RUG ISSUES 631, 633
(2008) [hereinafter Armstrong, Research Note] (noting
that 75% of Somali men use khat). U.S. pop culture
has even referenced the use of khat in Somalia, including
the 2001 Oscar-winning film Black Hawk Down.
See Black Hawk Down, INTERNET M OVIE D ATABASE,
http://w w w .im db.com/title/tt0265086/?ref=ttqt_qt_tt
(last visited July 8, 2013).



1
   “Street Names: Khat has over 40 street names to include
Abyssinian Tea, African Salad, Bushman’s Tea, Chat, Gat, Kat,
Miraa, Oat, Qat, Somali Tea, Tohai, Taschat.” Fact Sheet, KHAT
A KA : Catha Edulis, DRUG ENFORCEMENT ADMIN.,
http://www.justice.gov/d ea/pubs/pressrel/pr072606a.htm l
(last visited July 8, 2013).
4                                    Nos. 12-2792 & 12-2793

  Khat “the plant” is not illegal in the United States. It is
not listed in the U.S. Code or the Code of Federal Regula-
tions (CFR) controlled substances schedules. See, e.g.,
United States v. Hassan, 542 F.3d 968, 972 (2d Cir. 2008);
United States v. Caseer, 399 F.3d 828, 833 (6th Cir. 2005);
United States v. Hussein, 351 F.3d 9, 15 (1st Cir. 2003). The
plant, however, contains two controlled substances,
cathinone and cathine, that produce an energetic and
excited state that allows a user to combat fatigue
and function at a higher level. See U.S. Food and Drug
Administration, Basis for the Recommendation for Control
of Cathinone into Schedule I of the Controlled Substances Act
10, 12 (Nov. 5, 1992) [hereinafter FDA Report]. As a
result, cab drivers in the United States have been known
to use khat during their shifts.2 See Caseer, 399 F.3d at
831. “Fresh” khat is sold in “bundles,” costing approxi-
mately $40 to $70 in the United States. “Dried” khat, also
known as “garraba” or “G20,” is sold in packs or “baggies”
for about $40 each.
  Cathinone, a Schedule I drug, has properties similar
to those of amphetamine and is the stronger of the
two controlled substances found in khat leaves. It was
added to the U.S. Controlled Substance Act (CSA) in
1993.3 See 21 C.F.R. § 1308.11(f)(3); FDA Report, at 18.



2
  An audio recording of a call played at trial included a cab
driver saying he did nothing for hours during his shift
because he was too high from the garraba he chewed.
3
  Synthetic cathinone is one of the key ingredients in the
increasingly-popular recreational drug “bath salts.” See Drug
                                                (continued...)
Nos. 12-2792 & 12-2793                                            5

Cathine, on the other hand, is a Schedule IV controlled
substance and the weaker of the two. See 21 C.F.R.
§ 1308.14(f)(1). Not all khat leaves contain the same or
similar amounts of either substance, however; some
contain none. The regulation of khat then is dependent
upon the particular chemical composition of each leaf,
which may vary depending on the size of the plant
and when the plant was harvested. See Schedules of
Controlled Substances: Placement of Cathinone and 2,5-
Dimethoxy-4-ethylamphetamine Into Schedule I, 58 Fed.
Reg. 4316, 4317 (Jan. 14, 1993) (“When khat contains
cathinone, khat is a Schedule I substance. During either
the maturation or the decomposition of the plant mate-
rial, cathinone is converted to cathine, a Schedule IV
substance. . . . When khat does not contain cathinone, but
does contain cathine, khat is a Schedule IV substance.”).
  Once a khat plant or shrub is harvested, the cathinone
in the plant metabolically breaks down into the less
potent substance cathine. This breakdown occurs
roughly thirty to forty-eight hours after harvesting but,
again, varies depending on the particular plant and
whether steps are taken to preserve the plant’s initial
chemical composition. See Armstrong, Research Note, at
639. In other words, fresh khat leaves have a greater
ratio of cathinone to cathine than old, dried up leaves,



3
  (...continued)
Facts: Synthetic Cathinones (“Bath Salts”), N AT ’L I NST . ON D RUG
A BUSE , http://www.drugabuse.gov/publications/drugfacts/
synthetic-cathinones-bath-salts (last visited July 8, 2013).
6                                  Nos. 12-2792 & 12-2793

thereby producing greater psychoactive effects on the
user. This is why khat growers expedite the process
of harvesting the plants and shipping them to the
intended destinations: khat users purchase the leaves
for their desired effects, and a slow or delayed shipping
process naturally diminishes the effect of each leaf
upon consumption. See United States v. Abdulle, 564 F.3d
119, 125 (2d Cir. 2009) (“[A] newly harvested leaf may
contain cathinone, while the same leaf a few days later
may contain only cathine, the weaker, Schedule IV stimu-
lant.”). And at some point, khat leaves might not have
any trace of the controlled substances and ingesting
them would have the same effect as chewing leaves off
an oak tree. See Argaw v. Ashcroft, 395 F.3d 521, 526 (4th
Cir. 2005) (“At this juncture, there is no reasonable
basis for the conclusion that khat always contains
cathine.”). For this reason, khat generally arrives in the
United States within five or six days after it has been
harvested.
  The only way to determine whether a particular khat
leaf has cathinone or cathine is to chemically analyze it.
This is important because, unlike marijuana or peyote,
law enforcement personnel cannot determine whether
possession of a given khat plant is illegal by simply
looking at the plant. Cf. 21 C.F.R. §§ 1308.11(d)(23),
(d)(26) (listing “marijuana” and “peyote” as controlled
substances).


    B. The Facts
  Hussein Ahmed was a cab driver and known khat
dealer in the Indianapolis, Indiana area. Ahmed had
Nos. 12-2792 & 12-2793                                 7

“fresh” khat connections in Europe who would send
packages of it to him at: his residence, rented mailbox
stores, and the Somali House of Coffee (the coffee
house) before Mire became its owner. Once Ahmed
received a package, which usually contained 30 to 200
bundles of khat, he repackaged the bundles into smaller
quantities. This made for easier distribution of the
product to local street buyers stretching from
Indianapolis to Columbus, Ohio. One continuing problem
for Ahmed was that some of his packages of fresh khat
were intercepted by U.S. Customs officials. But for the
packages he did receive, he would send back money
using international money transfer businesses, including
Dahabshil, Inc., Amal Express, and Western Union. And
in doing so, he often used fake aliases to evade law en-
forcement detection.
  Ahmed also distributed “dried” khat, which he pur-
chased domestically, in boxes from Ethiopian sources.
These boxes contained plastic trash bags full of garraba
and weighed approximately 8 kilograms. One box cost
Ahmed anywhere from $800 to $1,600.
  Ahmed had another problem, however; he needed
help selling and distributing the khat he purchased. To
overcome it, he reached out to others for assistance. One
person Ahmed looked to was his roommate, Rafle, who
fled from Somalia in the 1990s and eventually landed in
Indianapolis. This made sense because Rafle was often
present when Ahmed opened the khat shipments
at their apartment and repackaged the “goods” for distri-
bution.
8                                   Nos. 12-2792 & 12-2793

  Rafle had two main roles in the conspiracy. First, he
often sent money back to Ahmed’s sources overseas on
Ahmed’s behalf. The amount would vary, but on one
particular occasion, Rafle sent $700 to a “Guleed Ismail” in
Holland. Guleed Ismail was one of Ahmed’s sources
for fresh khat from September 2007 until February 2011.
Additionally, Rafle was a truck driver by trade. Accord-
ingly, he could transport khat from Columbus to Indiana-
polis, and vice versa, while on the road. Government
wiretaps captured a few conversations between
Ahmed and Rafle when Rafle was commuting to and
from Columbus. One such wiretap involved a khat trans-
action that was to occur and included Ahmed
apprising Rafle to tell the seller that he was sent by the
“Sultan.” Another call included Ahmed advising Rafle
to “change to local roads,” and Ahmed testified that he
told Rafle to drive the speed limit to avoid law enforce-
ment scrutiny. Ahmed paid Rafle approximately $400
per trip in exchange for acting as his drug courier.
  Ahmed also wanted to distribute khat locally in a
secure setting in Indianapolis; that is how the Somali
House of Coffee and Mire became involved. Mire, born
in Mogadishu, Somalia, immigrated to the United States
with his family in 2004 and eventually made his way to
Indianapolis, Indiana. In early 2009, he became the sole
proprietor of the coffee house. The coffee house was
also known by its previous name, Hargeisa Coffee;
Hargeisa is a city in Somalia. It was at the coffee house
where Mire’s troubles began.
 Ahmed testified that in April 2009, shortly after Mire
purchased the coffee house, he reached out to Mire to
Nos. 12-2792 & 12-2793                                  9

discuss selling khat there. The former owner of the
coffee house, Handule Mohammed, was a player in
Ahmed’s khat conspiracy and previously allowed Ahmed
to send khat there. Testimony indicated that the
Somali community in Indianapolis was a tight-knit
group and was known to hang out at the coffee house
together.
  Ahmed thought the coffee house, now under Mire’s
direction and control, would be a good place to return
and sell khat. Mire, a new business owner, wanted to
increase profits at the coffee house, and Ahmed knew
that. Ahmed’s selling point was that his khat sales
would bring more customers to the coffee house and
Mire would see an increase in his legitimate business
sales in return. Mire agreed.
  Some time thereafter, Mire expanded the coffee house
to include a large room at the front of the building. This
room was decorated as a lounge and had dark-tinted
windows facing the street. The coffee house had other
smaller rooms at the back of the building. One of these
smaller rooms was where Ahmed kept the khat he
sold there. Ahmed did not have a key to that room, or
any other room, at the coffee house.
  Ahmed testified that he sold khat at the coffee house
about four to five times per week from approximately
April 2009 until April 2010, and this was done with
Mire’s knowledge and permission. During this time
period, the number of customers at the coffee house
increased: often times, there were as many as fifteen
to eighteen people chewing khat at a time. Testi-
10                                  Nos. 12-2792 & 12-2793

mony indicated that the renovated coffee house “lounge,”
with its tinted exterior windows and couches, served as
an ideal place to enjoy the substance. Many of the khat
users present were cab drivers in the area.
   In March 2010, Mire began selling khat at the coffee
house on his own. Ahmed in fact testified that Mire
went into business for himself; he did not supply Mire
with khat to sell, share in any of Mire’s profits, or assist
Mire in any pertinent way with respect to selling khat
at the coffee house after April 2010. A recorded conversa-
tion between Ahmed and his friend Sayid Awale on
September 17, 2010, corroborated that information.
Awale asked Ahmed where he could get “green leaves,”
another name for garraba, and Ahmed told him “the
little fat one who owns the place sells the stuff.” Ahmed
testified that “the little fat one” was Mire; context demon-
strates that “the stuff” was garraba and “the place” was
the coffee house.
  Other testimony indicating that Mire was knowingly
selling khat at the coffee house after April 2010 came
from Jafar Tuti, a cab driver in Chicago, Illinois.
Tuti rented a mailbox at a UPS store in Indianapolis in
September 2010; Mire was present with Tuti at the time.
Tuti had planned to move to Indianapolis from
Chicago, but when that did not occur, he gave Mire the key
to the UPS mailbox: instead of returning the key, Mire
continued to use the mailbox himself. Tuti paid
between $60 to $100 to rent the mailbox for three
months; Mire paid Tuti $800 to continue using it in Tuti’s
name. The owner of the UPS branch where the mailbox
Nos. 12-2792 & 12-2793                                 11

was located testified that only Mire was authorized to
receive packages at the mailbox.
  Unbeknownst to the Defendants, a confidential
human source (CHS) of Somali heritage, Ali Jama, tipped
off the FBI in an attempt to “clean up” the Somali com-
munity in Indianapolis; he wanted to eradicate the use
of khat. In April 2009, the CHS met with Special Agent
Todd Samargia and Task Force Officer Andy Burks and
told them that Ahmed, among others, was involved in a
khat-trafficking conspiracy in the area. The CHS said
the drug activity began around 2007 and explained the
details regarding how the khat was shipped to the
United States, where it was coming from, and how the
conspirators used fictitious information on the postal
labels. FBI agents used this information to launch an
investigation into the khat-distribution scheme in India-
napolis. The agents followed up on the CHS’s tip and
tracked the shipping of khat, conducted wiretaps on
individuals believed to be involved in the conspiracy,
engaged in surveillance of the coffee house, and had
the CHS participate in a few controlled drug buys of
khat at the coffee house.
   The information gathered led to two indictments
being returned against Ahmed, Rafle, Mire, and many
others in the Southern District of Indiana on February 15,
2011. On February 17, Mire was arrested, and a search
warrant was executed at the Somali House of Coffee.
The coffee house search turned up numerous large bags
filled with dried khat. Luke Augustine, a Senior Forensic
Chemist for the Drug Enforcement Administration,
12                                 Nos. 12-2792 & 12-2793

tested the khat plants seized for the presence of cathinone
and cathine. Some of the plants tested positive for
cathinone; some tested positive for cathine; and some
did not have a trace of either controlled substance.
  After Mire was arrested and informed of his Miranda
rights, FBI Special Agent Jeremy Michaelis asked Mire
about the khat found at the coffee house. Mire did not
just deny ownership of the bags; he said it must have
been placed there by his “enemies.” Furthermore, Mire
went so far as to say that he had never before seen
garraba in Indianapolis. Agent Samargia also had an
opportunity to speak with Mire. He showed Mire a photo-
graph of a man in the coffee house surrounded by
bags presumably of garraba. Mire denied knowing who
was in the photo, what was in the bags, or where the
photo was taken. Agent Samargia testified that the
photo was obtained from Mire’s personal cell phone,
which was found during the search of the coffee house.
  On July 12, 2011, a superseding indictment was filed;
eight individual defendants were named. Mire and Rafle
were both listed in Count I, conspiracy to possess with
intent to distribute cathinone in violation of 21 U.S.C.
§§ 841(a) and 846. Mire was also listed in Count II, know-
ingly using or maintaining a place for the purpose of
distributing and using cathinone in violation of 21 U.S.C.
§ 856(a)(1); and Count III, possession with intent to dis-
tribute a mixture or substance containing cathinone
in violation of 21 U.S.C. § 841(a). Five of the named indi-
viduals pleaded guilty in some capacity, including
Ahmed, who agreed to cooperate with the government
Nos. 12-2792 & 12-2793                                    13

in exchange for leniency. The case against Mire, Rafle,
and another co-conspirator continued.
  The government informed the Defendants that it in-
tended to call Dr. Augustine and Theresa Browning, DEA
Forensic Chemists, to testify as experts regarding the
testing of khat plants for cathinone. On October 7, 2011,
Mire filed a motion to exclude that testimony. 4 Rafle
joined the motion on March 12, 2012. The Defendants
contended that the testing procedures underlying the
experts’ testimony were unreliable and incomplete.
  The district court conducted a Daubert hearing on the
motion on March 19, 2012. See Daubert v. Merrell Dow
Pharms., 509 U.S. 579 (1993). On April 23, 2012, the
court denied the Defendants’ motion to exclude, as we
discuss in full detail below.
  A bench trial for Mire, Rafle, and the other co-conspirator
was held from March 12, 2012, through March 30, 2012.
The bulk of the government’s case came from Ahmed’s
testimony. Other significant testimony came from
Dr. Augustine, Agent Michaelis, and Agent Samargia. At
the close of the government’s case, all three defendants
moved for a judgment of acquittal pursuant to Federal


4
  Co-defendant Abdikadar Hodan filed the first motion to
exclude the government’s expert testimony, which Mire re-
quested to join on August 12, 2011. Hodan pleaded guilty to
the charges against him on September 1, 2011, so his motion
was rendered moot. By invitation of the district court, Mire
requested Hodan’s motion be reinstated and treated as if
Mire had originally filed it. The district court obliged.
14                                  Nos. 12-2792 & 12-2793

Rule of Criminal Procedure 29(a). They argued, among
other things, that (1) the CSA violated the Due Process
Clause of the Fifth Amendment because it did not
provide fair warning that the possession of khat could
be illegal; (2) the government did not prove they “knew”
khat contained a controlled substance; and (3) the gov-
ernment did not prove an “agreement” to violate 21
U.S.C. § 841(a) as required by the conspiracy count.
  On April 4, 2012, the district court found Rafle guilty on
Count I and Mire guilty on Counts I, II, and III. The
court found the third defendant not guilty.
   On April 23, 2012, the district court denied the
Rule 29(a) motions in their entirety; the court also issued
its factual findings and an entry of judgment as to Mire
and Rafle. Rafle was sentenced to a prison term of
twelve months and one day for his conviction on
Count I. The district judge sentenced Mire to sixteen-
month prison terms on Counts I, II, and III; the terms
to run concurrently.


                    II. DISCUSSION
  Mire and Rafle seek to have their convictions over-
turned. They each contend, first, that their due pro-
cess rights were violated because the CSA and its cor-
responding regulations do not provide fair warning
that the possession of khat may be illegal, and second,
that the district court erred under Daubert in admitting
the government’s expert testimony regarding the chem-
ical composition of the khat leaves tested. Mire puts
Nos. 12-2792 & 12-2793                                      15

forth two additional contentions: his conviction for con-
spiracy to distribute khat, 21 U.S.C. §§ 841(a)(1) and 846,
and his conviction for maintaining a place for the dis-
tribution or use of khat, 21 U.S.C. § 856(a)(1), violate
the Double Jeopardy Clause; and alternatively, the gov-
ernment did not present sufficient evidence sup-
porting each of his convictions. We address the four
contentions in turn.


  A. Fair Warning
  The Defendants’ “fair warning” argument is that the
CSA violates the Due Process Clause because the regula-
tions do not provide sufficient notice to persons of ordi-
nary intelligence that khat plants may contain cathinone
or cathine and, therefore, may be illegal to possess.
This argument is one of first impression in this Court,
but all of our sister circuits who have considered it have
rejected it. See United States v. Hassan, 578 F.3d 108, 122
(2d Cir. 2008); Caseer, 399 F.3d at 839; United States v.
Sheikh, 367 F.3d 756, 764 (8th Cir. 2004). We review this
question of law de novo, United States v. Ketchum, 201
F.3d 928, 934 (7th Cir. 2000), and join the other circuits
and reject it as well.
  The Due Process Clause requires a criminal statute
to “give fair warning of the conduct that it makes a
crime.” Bouie v. City of Columbia, 378 U.S. 347, 350-51 (1964).
The Clause is violated when “a criminal statute . . . fails
to give a person of ordinary intelligence fair notice that
his contemplated conduct is forbidden by the statute.
The underlying principle is that no man shall be held
16                                  Nos. 12-2792 & 12-2793

criminally responsible for conduct which he could not
reasonably understand to be proscribed.” United States
v. Harriss, 347 U.S. 612, 617 (1954). But we will strike
down a statute only when it contains “terms so vague
that [persons] of common intelligence must necessarily
guess at its meaning and differ as to its application.”
Gresham v. Peterson, 225 F.3d 899, 907 (7th Cir. 2000)
(quoting Roberts v. United States Jaycees, 468 U.S. 609,
629 (1984)).
  The issue here is not whether the statute is vague in
and of itself. The CSA specifically provides that
cathinone and cathine are controlled substances. See 21
C.F.R. §§ 1308.11(f)(3), 1308.14(f)(1). No one disputes
that. Rather, the Defendants maintain that, even though
cathinone and cathine are specifically prohibited, “the
regulations do not give an ordinary person any indica-
tion that khat is illegal, and in fact, tend to suggest that
it is not illegal.” This argument is based on the fact
that “khat” is not listed in the CSA or the regulations,
yet it still may be illegal to possess at certain times, de-
pending on the chemical composition of a particular
plant or leaf—i.e., whether it contains cathinone or
cathine, two terms that are unfamiliar to most people.
We are thus looking at a statute that may be more ap-
propriately described as “underinclusive,” because
persons of ordinary intelligence would not necessarily
know that khat is (or contains) a controlled substance
even after reading the statutory text, as opposed to a
statute that cannot be understood on its face. See Caseer,
399 F.3d at 836 (explaining that cathinone is an
“obscure scientific term” and “the controlled substances
Nos. 12-2792 & 12-2793                                   17

schedule’s vagueness derives not from the language’s
imprecision but rather from the schedule essentially
being written in a language foreign to persons of
ordinary intelligence”). And in these situations, the risk
of an individual being “trapped” is high. The Supreme
Court in Bouie explained,
    When a statute on its face is vague or overbroad, it
    at least gives a potential defendant some notice, by
    virtue of this very characteristic, that a question
    may arise as to its coverage, and that it may be held
    to cover his contemplated conduct. When a statute on
    its face is narrow and precise, however, it lulls the
    potential defendant into a false sense of security,
    giving him no reason even to suspect that conduct
    clearly outside the scope of the statute as written
    will be retroactively brought within it by an act of
    judicial construction.
Bouie, 378 U.S. at 353.
  The government puts forth two contentions as to why
the situation discussed in Bouie is not present here. First,
the government says that the Supplementary Informa-
tion published in the Federal Register explains the con-
nection between cathinone, cathine, and khat. The Gov-
ernment is partially correct; the Supplementary Infor-
mation does discuss the connection. See 58 Fed. Reg. 4317
(discussing the connection between cathinone, cathine,
and khat); see also Schedules of Controlled Sub-
stances; Temporary Placement of Cathine ((+)-
norpseudoephedrine), Fencamfamin, Fenproporex and
Menfenorex Into Schedule IV, 53 Fed. Reg. 17459 (May 17,
18                                 Nos. 12-2792 & 12-2793

1988) (discussing the connection between cathine
and khat). That information, however, was never incorpo-
rated or published in the CFR, and there is no reference
to khat in the CFR. See Hussein, 351 F.3d at 13.
   Next, the government directs us to the U.S. Sentencing
Guidelines, which provide a marijuana equivalency
for khat-related offenses even though neither cathinone
nor cathine are explicitly mentioned. See U.S.S.G. § 2D1.1,
comment. n.8(D) (listing one gram of khat as being equiva-
lent to 0.01 grams of marijuana). But on these facts, we
simply cannot accept the government’s contention that
this additional information cures the “underinclusive”
problem. Many of the questions during oral argument
focused on the general nature of khat—e.g., how the
word is pronounced, what it is, how it is used, who uses
it, and what its effects are. With these questions in
mind, an ordinary person would not understand or
generally know that khat contains two controlled sub-
stances, let alone cathinone and cathine. See Caseer, 399
F.3d at 838-39 (rejecting the government’s arguments
that the Supplementary Information and the Sentencing
Guidelines cure “a vague criminal statute of its constitu-
tional defect”).
   The government is not without recourse, however; a
lifeline is available. The Supreme Court has noted that
“a scienter requirement may mitigate a law’s vagueness,
especially with respect to the adequacy of notice to
the complainant that his conduct is proscribed.” Vill. of
Hoffman Estates v. Flipside, Hoffman Estates, 455 U.S. 489,
499 (1982). The statutes at issue here require “actual
Nos. 12-2792 & 12-2793                                      19

knowledge” that khat contains a controlled substance;
they contain a scienter requirement. See 21 U.S.C.
§§ 841(a)(1), 856(a)(1) (requiring that the defendant com-
mitted the offense “knowingly” or “intentionally”).
Accordingly, the Defendants could not have been con-
victed of violating the statutes unless they had actual
knowledge that khat—fresh or dried—contains a con-
trolled substance. See Hassan, 578 F.3d at 120-21; Caseer,
399 F.3d at 839, 841-42; Hussein, 351 F.3d at 14-19. This
requirement saves the statutes. See Hassan, 578 F.3d at 120-
21; Caseer, 399 F.3d at 839, 841-42; Hussein, 351 F.3d at 14-
19; see also Boyce Motor Lines, Inc. v. United States, 342 U.S.
337, 342 (1952) (“The statute punishes only those who
knowingly violate the Regulation. This requirement of
the presence of culpable intent as a necessary element
of the offense does much to destroy any force in the
argument that application of the Regulation would be
so unfair that it must be held invalid.”).
  Like our sister circuits who have considered the reg-
ulations involving khat, we are mindful that “it would
be helpful to people, who actually resort to statutes
and regulations to determine whether their conduct is
lawful, for Congress, through the statutory or regulatory
scheme, to include the word ‘khat’ in the CSA.” Hassan,
578 F.3d at 121. This is especially true considering that
not all khat leaves contain cathinone or cathine and
that other plants containing controlled substances are
specifically listed in the schedules. See Caseer, 399 F.3d
at 847-50 (Holschuh, J., dissenting) (discussing other
plants, like marijuana, peyote, the poppy plant, and coca
leaves, that are “themselves listed in the schedules by
20                                    Nos. 12-2792 & 12-2793

their commonly known names”) (emphasis omitted). But
this does not invalidate the statutes at issue on
Due Process grounds; the Defendants’ fair warning chal-
lenge fails.5


    B. Expert Testimony under Daubert
  The Defendants’ second challenge is to the admission
under Daubert of the government’s expert testimony
regarding the presence of cathinone and cathine in the
khat plants tested. Federal Rule of Evidence 702 permits
expert testimony on an issue, provided the testimony is
helpful to the trier of fact, is based on sufficient facts
or data, and is the product of reliable principles and
methods. Fed. R. Evid. 702. The district court is tasked
with determining whether the requirements of Rule 702
are satisfied. Bielskis v. Louisville Ladder, Inc., 663 F.3d
887, 893 (7th Cir. 2011) (citing Daubert, 509 U.S. at 589). In
doing so, the court considers a non-exhaustive list of
guideposts: (1) whether the scientific theory on which
the expert’s testimony is based can be or has been
tested; (2) whether the theory has been subjected to peer
review and publication; (3) the known and potential
rate for error; and (4) whether the theory has been gener-
ally accepted in the relevant scientific, technical, or profes-
sional community. Am. Honda Motor Co. v. Allen, 600
F.3d 813, 817 (7th Cir. 2010) (citing Daubert, 509 U.S. at 593-


5
  To the extent the Defendants attempt to bring the Equal
Protection clause into the purview of their fair warning chal-
lenge, we reject this without further discussion.
Nos. 12-2792 & 12-2793                                   21

94); Bradley v. Brown, 42 F.3d 434, 437 (7th Cir. 1994).
We give the district court “wide latitude” in performing
this gate-keeping function and determining whether
expert testimony is admissible. Lapsley v. Xtek, Inc., 689
F.3d 802, 810 (7th Cir. 2012).
  The government called Dr. Augustine, a DEA Forensic
Chemist, to testify at trial regarding the results from
his analysis of the khat plants seized and tested.
Dr. Augustine testified that many of the plants he
analyzed tested positive for the controlled substances
cathinone and cathine. He also testified that there were
some plants that did not include either of the controlled
substances.6 The Defendants objected to this testimony
before trial, contending that it was not based on reliable
methodology. The district court held a Daubert hearing
on the issue.
  At the hearing, the government called John Chappell,
another DEA Forensic Chemist, to testify regarding
the procedures and methods Dr. Augustine used to
analyze khat for the presence of cathinone and cathine.
Dr. Chappell testified that the proposed testimony was
based on an analysis of the plant material using a
process called gas chromatography-mass spectrometry,
also known as “GC-MS.” GC-MS yields a “qualitative”
result, as opposed to a “quantitative” result. Dr. Chappell
explained that the difference between the two “results” is
that a qualitative analysis involves testing the plant for


6
  The khat plants with a “negative” result had no bearing on
the prosecution of the Defendants.
22                                    Nos. 12-2792 & 12-2793

the presence of a particular substance while ruling out
the possibility of other substances being present; a quanti-
tative analysis determines the particular amount of the
substance tested for in the plant. DEA procedures do
not require quantitative testing of khat.
   With respect to GC-MS testing as utilized to detect the
presence of cathinone and cathine in khat, Dr. Chappell’s
testimony encompassed the non-exhaustive Daubert
factors. He first discussed several studies and published
literature detailing the use of GC-MS to detect cathinone
and cathine in khat. Next, Dr. Chappell stated that GC-MS
methodology had been subjected to various peer-review
studies and directed the court to several peer-
reviewed publications, including one that he co-authored.
See John S. Chappell & Marsha M. Lee, Cathinone preserva-
tion in khat evidence via drying, FORENSIC S CIENCE INTERNA-
TIONAL, Feb. 25, 2010, at 108-120; Marsha M. Lee, The
Identification of Cathinone in Khat (Catha edulis): A
Time Study, 40 J. F ORENSIC S CI. 116 (1995). With respect
to the third factor, he described the rate of error as “infini-
tesimal.” Finally, Dr. Chappell testified that GC-MS
testing was a proper and common way to analyze khat
plants for the presence of cathinone and cathine.
  In response, the Defendants called Daniel McCoy, a
toxicologist for over thirty years, to testify that the tests
were inadequate. Dr. McCoy testified that the tests were
inadequate because they did not include a “limit of
blank,” a “limit of detection,” or a “quantitative compo-
nent.” A limit of blank is the “highest apparent analyte
concentration expected to be found when replicates of
Nos. 12-2792 & 12-2793                                    23

a sample containing no analyte are tested”; a limit of
detection is the “lowest analyte concentration likely to
be reliably distinguished from the [limit of blank] and
at which detection is feasible.” David A. Armbruster &
Terry Ply, Limit of Blank, Limit of Detection and Limit of
Quantitation, 29 C LIN. B IOCHEM . R EV. S49, S49-52 (Supp. I
Aug. 2008), available at http://www.ncbi.nlm.nih.gov/
pmc/articles/PMC2556583/. These assertions as to why
Dr. Augustine’s testing was unreliable, which the district
court rejected after applying Daubert, are the same as
those the Defendants present on appeal. We thus look
to whether the district court’s rejection of these
arguments was “manifestly erroneous.” See Lapsley, 689
F.3d at 809.
  In its written decision denying the Defendants’ motion
to exclude, the district court addressed the issue of
false positives. The court noted Dr. Chappell’s testimony
that the qualitative analysis uses “negative controls” as
“blanks” to verify that there is no “independent source
of contamination in the preparation of the sample for
analysis.” The court also noted that GC-MS analysis
requires the tester to make sure that the “testing instru-
ment” is not contaminated by a substance not actually
present in the object tested. In the event of a “false posi-
tive,” that sample result is invalidated and tossed out.
We think this discussion was sufficient for the court to
conclude that the rate of error in the testing was low,
a critical guidepost under Daubert.
  The district court next addressed the issue of limit of
blank and limit of detection in the testing. The court
24                                 Nos. 12-2792 & 12-2793

noted Dr. Chappell’s testimony that these terms, and
their corresponding meanings, are not generally applied
in forensic drug analysis. Dr. Chappell had previously
explained,
     These terms are not generally applied in the forensic
     drug analysis of solid dosage forms because they are
     much simpler mixtures as opposed to toxicology,
     which involves, invariably, bodily fluids like blood
     or urine, which are very complex samples and also
     have typically very low concentrations of drug sub-
     stances, as I understand.
The district court also considered Dr. Chappell’s testi-
mony that in forensic evidence, these terms are not as
important because the materials he and Dr. Augustine
deal with, as opposed to other toxicologists, are “usually
much more concentrated in the amount of the drug sub-
stance” being analyzed and are “simpler mixtures.” And
more importantly, the testers are not limited to a
certain sample size. As Dr. Chappell testified, “If the
[sample size] turns out to be inadequate for the detec-
tion or identification of a controlled substance, it’s
possible to take more material, examine it again, and be
able to eventually maybe see whether there is some-
thing more present in a sample.” This information,
coupled with the Defendants’ failure to point to any-
thing undermining it, adequately supports the district
court’s conclusion that the GM-CS testing of the leaves
did not need a “limit of detection” or a “limit of blank”
to be admissible.
 The Defendants’ final argument, that the testing was
unreliable because it did not encompass a quantitative
Nos. 12-2792 & 12-2793                                    25

component, is without support. The Defendants do not
assert that the testing for the presence of cathinone or
cathine can never be done; they concede that science
can determine “trace” amounts of the substances.
Instead, their argument is framed around a misguided
belief that a precise amount of the substance needs to be
calculated. In making this argument, they liken the situa-
tion here to the fact that the majority of dollar bills in
the United States have traces of cocaine on them, see
Theresa K. Casserly, Evidentiary and Constitutional Implica-
tions of Employee Drug Testing Through Hair Analysis, 45
C LEV. S T. L. R EV. 469, 474 n.49 (1997) (“In Miami, it is
reported that there is cocaine on every dollar bill.” (citing
Constance Holden, Hairy Problems for New Drug Testing
Method, SCIENCE, Sept. 1990, at 1099)), and people are
not put in jail for the possession of dollar bills. But as
we pointed out at oral argument, people do not ingest
dollar bills to get the effects of cocaine (at least not rea-
sonably); people do chew khat leaves for the stimulant
effects.
  Furthermore, the CSA and its accompanying regula-
tions prohibit the possession of cathinone if it can affect
the nervous system, regardless of the amount. See 21
C.F.R. § 1308.11(f) (explaining that cathinone in
Schedule I includes “any material, compound, mixture,
or preparation which contains any quantity . . . having
a stimulant effect on the central nervous system”) (em-
phasis added). It is irrelevant as to whether the
precise amount of the controlled substance found in a
khat plant could actually produce the effects the user
desires; a “trace” amount can have a stimulant effect on
the nervous system even if the user does not get “high.”
26                                   Nos. 12-2792 & 12-2793

To find in the Defendants’ favor, we would have to
write an additional element into the offenses: that khat
leaves must have a “certain amount” of cathinone
versus “any quantity.” That is not our job, and we
decline to do so. See Urnikis-Negro v. Am. Family Prop.
Servs., 616 F.3d 665, 684 (7th Cir. 2010) (stating that “[o]ur
job is to apply the statute as Congress has written it”).
Finally, the fact that one khat plant may be illegal to
possess (because it contains a controlled substance)
whereas another may be completely legal (because
the controlled substances have fully broken down
into others) makes no difference in this case or to the
application of the Daubert analysis. The Defendants’
argument that a qualitative assessment is insufficient
because it does not say “how much” cathinone or cathine
is in a given leaf or plant easily fails; the district court
correctly rejected it.
  As to the Defendants’ other arguments, including
that the research articles Dr. Chappell discussed were
not peer reviewed and that there were other “serious
defects in the methods used by the government chemists
to test the khat materials,” we have considered them
and find them unpersuasive. The record establishes that
the district court properly followed Daubert and did
not abuse its discretion by admitting the government’s
expert testimony.


  C. Double Jeopardy
  Mire argues that his convictions and subsequent sen-
tences under 21 U.S.C. §§ 841(a)(1) and 846 (conspiracy
Nos. 12-2792 & 12-2793                                    27

to possess with intent to distribute cathinone) and 21
U.S.C. § 856 (knowingly maintaining a place for the
distribution or use of cathinone) violate the Double Jeop-
ardy Clause. This challenge was not raised in the
district court, so we review for plain error. See United
States v. Fluker, 698 F.3d 988, 1003 (7th Cir. 2012).
  The Double Jeopardy Clause states that no person shall
“be subject for the same offense to be twice put in
jeopardy of life or limb.” U.S. C ONST. amend. V. In other
words, “a person may not be convicted and punished for
two separate offenses arising out of the same act
unless ’each [offense] requires proof of a fact which the
other does not.’ ” United States v. Larsen, 615 F.3d 780, 786
(7th Cir. 2010) (quoting Blockburger v. United States, 284
U.S. 299, 304 (1932)). Our inquiry, also known as the
Blockburger test, takes us to the elements of the offenses
at issue: “[i]f each statute contains an element that the
other does not, then the offenses are different. If one
statute has an element missing from the second, but all
of the second’s elements are in the first, then the second
is a lesser included offense of the first.” United States
v. Loniello, 610 F.3d 488, 491 (7th Cir. 2010). Only in the
latter situation is the Double Jeopardy Clause violated.
  A conviction for conspiracy under 21 U.S.C. §§ 841(a)
and 846 required the government to prove beyond a rea-
sonable doubt that: (1) there was a conspiracy to possess
cathinone with an intent to distribute it, and (2) Mire
knowingly or intentionally became a party to the agree-
ment. A conviction under § 856, however, required the
government to prove that: (1) Mire knowingly used or
28                                 Nos. 12-2792 & 12-2793

maintained a place, and (2) he did that for the purpose of
distributing or using cathinone. Looking at these
offenses and their elements, it is clear on their face that
there is no Double Jeopardy violation. Mire acknowl-
edges that the conspiracy count required proof of an
“agreement”; there is no agreement requirement for a
conviction under § 856. Mire also acknowledges that a
conviction under § 856 required proof that a defendant
“used or maintained a place”; there is no similar
element in §§ 841(a) or 846.
  That the conspiracy offense “functionally” has no
element that § 856 does not have because of the facts of
this case, as Mire asserts, makes little difference. Even
assuming that the agreement for the conspiracy to violate
§ 841(a) involved Mire’s ability to “maintain a place”—the
Somali House of Coffee—it is well-settled that “the com-
mission of a substantive offense and the conspiracy to
commit that offense are two separate crimes.” United States
v. Somers, 950 F.2d 1279, 1283 (7th Cir. 1991). If that is
the case, surely the principle of “two separate crimes”
applies to a conspiracy offense and an offense com-
pletely separate from the substantive offense of the con-
spiracy. Furthermore, proof of an “overt act,” or that
Mire actually maintained the Somali House of Coffee for
the purpose of distributing or using cathinone, is not
required for a conspiracy conviction. See United States v.
Nunez, 673 F.3d 661, 663 (7th Cir. 2012). As we explained,
proof of an overt act was required for a conviction
under § 856. There is nothing special about this case or
the offenses charged that takes it outside the reach of
these long-standing principles.
Nos. 12-2792 & 12-2793                                   29

  The facts underlying each conviction no doubt overlap.
But the offenses are effectively different, and we
presume Congress intended separate punishments for
each offense. See United States v. Faulds, 612 F.3d 566, 569
(7th Cir. 2010); United States v. Xiong, 595 F.3d 697, 698
(7th Cir. 2010). Mire’s Double Jeopardy challenge fails.


  D. Sufficiency of the Evidence
  Mire’s final challenge is to the sufficiency of the
evidence underlying all three of his convictions. His first
contention is the government did not prove the “actual
knowledge” element in each count—i.e., that Mire “knew”
khat plants contained a controlled substance. See 21
U.S.C. §§ 841(a)(1), 846, and 856(a)(1). His second conten-
tion is the government did not prove the “agreement”
required for the conspiracy conviction under 21 U.S.C.
§ 846. Our inquiry on these questions is whether “after
viewing the evidence in the light most favorable to
the prosecution, any rational trier of fact could have
found the essential elements of the crime beyond a rea-
sonable doubt.” Jackson v. Virginia, 443 U.S. 307, 319
(1979). And in making this determination, it is axiomatic
that we will not “weigh the evidence or second-guess
the [trier of fact’s] credibility determinations.” United
States v. Stevens, 453 F.3d 963, 965 (7th Cir. 2006). Thus,
we will only overturn a verdict for insufficiency of the
evidence “if the record is devoid of the evidence from
which a reasonable jury could find guilt beyond a rea-
sonable doubt.” United States v. Stevenson, 680 F.3d 854,
856 (7th Cir. 2012).
30                                   Nos. 12-2792 & 12-2793

  We begin with Mire’s contention that he did not “know”
khat contained a controlled substance, specifically,
cathinone. Initially, it is important to note that the
mens rea for the offenses charged—21 U.S.C. §§ 841(a)(1),
846, and 856(a)(1)—only required the government to
prove that Mire conspired to distribute, maintained a
place to distribute, or possessed with intent to distribute
any controlled substance. See, e.g., Abdulle, 564 F.3d at 126;
Hussein, 351 F.3d at 18; see also United States v. Turcotte,
405 F.3d 515, 526 n.2 (7th Cir. 2005) (acknowledging the
Hussein case and stating the “baseline principle that
defendants must know that the substances in
their possession are controlled substances to be con-
victed under the CSA, even if they do not know the
exact identity of the substance they possess”). It does not
matter whether Mire knew that khat contained cathinone
or cathine; all that matters is Mire knew that khat con-
tained an illegal substance. This distinction is key
because having to prove a defendant knew the particular
controlled substance at issue would be a much more
difficult undertaking.
  Unlike many of the cases in which we review a suffi-
ciency of the evidence claim, Mire’s trial was a bench trial.
We therefore know exactly what evidence the trier of
fact relied on when rendering his decision. Here, in the
entry of judgment, the district judge specifically dis-
cussed Mire’s statements to Agent Michaelis in which
he denied having ever seen khat or owning the khat
found at the Somali House of Coffee, in addition to
Mire’s statement that the khat had been placed there by
his “enemies.” As the district judge wrote, “Denial of
Nos. 12-2792 & 12-2793                                   31

ownership of the khat and deflecting responsibility for
it are strong circumstantial evidence that Mire knew
that the khat contained an illegal substance.” We agree
with the judge’s assessment of the information and
cannot say that no rational jury could reach the same
conclusion. See United States v. Skidmore, 894 F.2d 925, 928
(7th Cir. 1990) (concluding that the defendant’s “denial
of ownership reinforce[d] the inference that he knew
about the presence of cocaine”). Mire’s contention that
the government did not prove that he “knew” khat con-
tained a controlled substance is wrong.
  We move to Mire’s argument regarding the “agreement”
requirement of his conspiracy conviction. See 21 U.S.C.
§ 846; United States v. Speed, 656 F.3d 714, 717 (7th Cir.
2011) (explaining that the government must show an
agreement between two or more persons to engage in
criminal conduct to attain a conviction for conspiracy).
Ahmed testified at trial that in 2009, before he started
selling khat at the coffee house, he had a conversation
with Mire about selling khat there. Ahmed also
testified that the parties agreed that selling khat at the
coffee house would bring in more customers and
increase business for Mire. That is what occurred.
Between 2009 and March 2010, Ahmed sold khat at
the coffee house, and Mire allowed khat to be stored in
an unlocked back room of the building. Ahmed said
he did not have keys to the room; we can
thus presume that Mire, as the owner and operator
of the coffee house, held the keys and permitted the
khat’s storage there. In other words, if Mire did not want
32                                   Nos. 12-2792 & 12-2793

khat there, he could have easily prevented it by simply
locking the door. The district judge found Ahmed’s
testimony both credible and persuasive, and we have no
reason to disagree with those findings. We also be-
lieve Ahmed’s testimony demonstrates overwhelmingly
that the parties operated under an agreement and had
a mutually-beneficial relationship: Ahmed sold khat at
the coffee house; individuals went to the coffee house
for the khat; and once the individuals were at the coffee
house, they purchased legitimate items like coffee, tea,
and sandwiches. An important factor in the success of
any retail business is foot traffic. Like a saloon that
offers video poker to attract patrons, Mire’s agreement
with Ahmed brought in the customers necessary to
keep the Somali House of Coffee afloat.
  It is true that Mire started selling khat on his own in
March or April 2010, but that did not undo the
conspiracy (or the agreement) that had already occurred.
See United States v. Read, 658 F.2d 1225, 1233 (7th Cir. 1981)
(explaining that a participant may withdraw from a
conspiracy, but he is “still liable . . . for his previous
agreement and for the previous acts of his co-conspirators
in pursuit of the conspiracy”). The information in the
record precludes Mire from convincing us that no
rational jury could conclude he and Ahmed were parties
to an agreement. Thus, Mire’s challenge to his con-
spiracy conviction suffers the same fate as all the other
challenges on appeal.
Nos. 12-2792 & 12-2793                                33

                  III. CONCLUSION
  Having now described the underground world of
“khat,” and for the reasons discussed above, we A FFIRM .




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