                  FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                    No. 06-10538
                  Plaintiff-Appellee,
                 v.                            D.C. No.
                                            CR-91-00446-FRZ
FELIPE DE JESUS CORONA-VERBERA,
                                               OPINION
              Defendant-Appellant.
                                        
        Appeal from the United States District Court
                 for the District of Arizona
         Frank R. Zapata, District Judge, Presiding

                  Argued and Submitted
        October 15, 2007—San Francisco, California

                   Filed December 7, 2007

       Before: Robert R. Beezer, Stephen S. Trott, and
               N. Randy Smith, Circuit Judges.

                   Opinion by Judge Trott




                            16037
              UNITED STATES v. CORONA-VERBERA           16041


                         COUNSEL

Andrea L. Matheson, Matheson Law Firm, P.C., Tucson, Ari-
zona, for the defendant-appellant.

George Ferko, Assistant United States Attorney, Tuscon, Ari-
zona, for the plaintiff-appellee.


                         OPINION

TROTT, Circuit Judge:

   Felipe de Jesus Corona-Verbera (“Corona-Verbera”)
appeals his jury conviction and four concurrent eighteen-year
sentences for (1) conspiracy to import cocaine in violation of
21 U.S.C. §§ 952(a), 960(a)(1), 960(b)(1)(B)(ii), and 963; (2)
conspiracy to possess with intent to distribute marijuana and
cocaine in violation of 21 U.S.C. §§ 841(a)(1), 841(b)(1)
(A)(vii), 841(b)(1)(A)(ii)(II), and 846; (3) importation of
cocaine in violation of 21 U.S.C. §§ 952(a), 960(a)(1), and
960(b)(1)(B)(ii), and 18 U.S.C. § 2; and (4) possession with
intent to distribute cocaine in violation of 21 U.S.C.
§§ 841(a)(1) and 841(b)(1)(A)(ii)(II), and 18 U.S.C. § 2. We
16042          UNITED STATES v. CORONA-VERBERA
must decide (1) whether a nearly five-year delay between
events giving rise to the indictment and the return of the
indictment constituted a due process violation; (2) whether, in
spite of a nearly eight-year delay between the indictment and
arrest, our government was diligent in searching for Corona-
Verbera and bringing him to trial; (3) whether there was suffi-
cient evidence to convict Corona-Verbera on all four counts;
and (4) whether four concurrent eighteen-year sentences were
unreasonable. We have jurisdiction under 28 U.S.C. § 1291,
and we affirm.

                                 I

                       BACKGROUND

   The Sinaloa Cartel, led by Joaquin Guzman Loera (“El Chap-
po”),1 was one of the largest drug trafficking organizations in
Mexico during the late 1980s. One of El Chappo’s “top aids,”
co-conspirator Angel Martinez-Martinez (“Martinez”), testi-
fied at Corona-Verbera’s trial that the purpose of the Sinaloa
Cartel was to obtain drugs, primarily cocaine, and smuggle
the drugs into the United States for sale.

   Corona-Verbera’s current legal troubles stem from his
involvement with the Sinaloa Cartel. The story, as it pertains
to Corona-Verbera, began in May of 1990, when, as a result
of a tip, United States Customs agents set up surveillance on
a warehouse in Douglas, Arizona (“Douglas Warehouse”).
The agents followed a flatbed truck from the Douglas Ware-
house to a farmhouse complex in Queen Creek, Arizona
(“Queen Creek Complex”). They maintained surveillance on
the Queen Creek Complex for two days. During those two
days of surveillance, law enforcement officials observed
“flashes” emanating from inside one of the structures that
they believed were caused by either welding or cutting with
a torch.
  1
   Also referred to as Chappo Guzman.
               UNITED STATES v. CORONA-VERBERA            16043
   On May 11, 1990, agents obtained and executed a search
warrant for the Queen Creek Complex. During the search,
they discovered an empty false compartment underneath the
bed of the flatbed truck they had followed from the Douglas
Warehouse. The agents subsequently seized 2,037 pounds of
cocaine from boxes in a building in the Queen Creek Com-
plex.

   Following the Queen Creek seizure, on May 17, 1990, the
agents executed a search warrant at the Douglas Warehouse.
To their surprise, they discovered a steel drainage grate in the
floor covering a door disguised as a concrete plate. The door
could not be opened manually, so agents used a jackhammer
to break through it. Underneath, they found a tunnel.

   The tunnel (“Douglas Tunnel”) was approximately 200 feet
long and ran from the Douglas Warehouse under the border
to the home of Francisco Camarena-Macias (“Camarena”) in
Agua Prieta, Mexico. Martinez testified that Camarena was El
Chappo’s attorney. The concrete-lined tunnel was equipped
with a cart similar to a miner’s cart, electricity, a ladder, an
air compressor system, a pulley system like that of an eleva-
tor, and tubular piping that was used to drain water from the
tunnel.

  On the Mexico side, the tunnel was accessed by activating
a hydraulic system inside the Camarena residence. When the
agents turned on what appeared to be a water spigot located
outside of the house, the spigot activated the hydraulic system
and raised a false sub-floor under a pool table, revealing the
entrance to the tunnel.

   At Corona-Verbera’s trial, Martinez testified that one of the
Sinaloa Cartel’s primary entry points for smuggling drugs was
the Agua Prieta, Mexico and Douglas, Arizona border. He
said that to facilitate moving drugs from Mexico into the
United States, El Chappo asked Corona-Verbera to build a
tunnel between Agua Prieta and Douglas. Martinez testified
16044         UNITED STATES v. CORONA-VERBERA
that El Chappo told him that “the architect Corona made me
a f****** cool tunnel.”

   Martinez further testified he first met Corona-Verbera at El
Chappo’s residence in 1987. At that time, El Chappo intro-
duced Corona-Verbera as “the architect Corona.” Martinez
said he “never saw anybody except architect Corona refer to
Mr. Chappo Guzman in the informal ‘tu.’ ” He testified also
that Corona-Verbera had built other structures for El Chappo,
and had previously used hydraulic systems to design hidden
underground “clavos,” or stashes, for El Chappo. Adalberto
Romero (“Romero”), an employee at Douglas Redi-Mix in
Arizona, testified that he received a shipment of equipment
consisting of pistons “like a hydraulic lift,” water pumps, and
generators for delivery into Mexico. When he questioned
Corona-Verbera and Camarena about the equipment, they told
him it was for a gas station in Guadalajara, Mexico.

   William Woods (“Woods”), a contractor who poured con-
crete at the Douglas Warehouse, testified that he had been
Corona-Verbera’s friend. He said Corona-Verbera was the
architect at the warehouse and was at the site “throughout the
whole construction.” Woods said that Corona-Verbera told
him that the warehouse was supposed to be a washbay for
trucks. He testified also that Corona-Verbera told him that the
drains Woods’ crew had installed at the site were too small
and to tear them out.

   Woods’ testimony was corroborated by Boniface Lomeli
(“Lomeli”), a concrete construction worker at the warehouse,
and by Romero, who continued to work for Douglas Redi-
Mix after Camarena bought the company. Lomeli testified
that Corona-Verbera told him the purpose of the warehouse
was to wash trucks. However, there was no plumbing or water
in the warehouse. Lomeli testified also that the drainage
grates in the warehouse were too high for water to drain.
Lomeli testified further that Corona-Verbera had him rip out
otherwise functional two-by-two drains that had been
              UNITED STATES v. CORONA-VERBERA            16045
installed at the warehouse and replace them with two-by-four
drains, regardless of the cost. The two-by-four drains con-
cealed the door to the tunnel. Romero testified he told
Corona-Verbera that there was no place for the drainage to
actually drain, and Corona-Verbera told him it was none of
his business and to pour the cement.

   Shortly after the discovery of the tunnel, Corona-Verbera
was charged in the District of Arizona on May 25, 1990, by
complaint, with drug crimes, and a warrant was issued for his
arrest.

  The first indictment in this case was returned in 1988. On
March 24, 1993, a federal grand jury returned a superceding
indictment against others involved in the conspiracy, but still
did not name Corona-Verbera as a defendant. On April 26,
1995, a federal grand jury returned a second superceding
indictment. This indictment named Corona-Verbera as a
defendant. A third superceding indictment also naming
Corona-Verbera as a defendant was returned on August 8,
2001. Corona-Verbera was arrested in Mexico pursuant to a
provisional arrest warrant on January 23, 2003. Extradition
was granted to the United States on March 20, 2003.

   Corona-Verbera’s first appearance in court in the United
States was on February 11, 2004. He subsequently asked for
eight continuances, the first on March 4, 2004, and the last on
October 7, 2005. On March 9, 2006, the district court judge
denied Corona-Verbera’s motions to dismiss for pre-
indictment delay and violation of constitutional speedy trial
rights. His trial began on March 14, 2006 and a guilty verdict
was returned on March 29, 2006.

   The pre-sentence report determined that Corona-Verbera’s
total offense level was forty. After applying a two-level
enhancement because Corona-Verbera used his skills as an
architect to facilitate the crime, the report recommended a
sentence of 292 months due to the quantity of cocaine
16046         UNITED STATES v. CORONA-VERBERA
involved. At the sentencing hearing on August 21, 2006,
Corona-Verbera objected to the two-level enhancement and to
the recommended sentence because of the disparity between
his recommended sentence and those of his co-conspirators.
In its discretion, the district court sentenced Corona-Verbera
to four concurrent eighteen-year sentences, a downward
departure of more than six years, based on the disparity in
sentencing with respect to his co-conspirators. The district
court awarded Corona-Verbera credit for time served dating
back to his arrest in Mexico.

                              II

                       DISCUSSION

  A.    Pre-Indictment Delay

   [1] “The Fifth Amendment guarantees that defendants will
not be denied due process as a result of excessive preindict-
ment delay.” United States v. Sherlock, 962 F.2d 1349, 1353
(9th Cir. 1989). Generally, any delay between the commission
of a crime and an indictment is limited by the statute of limi-
tations. United States v. Huntley, 976 F.2d 1287, 1290 (9th
Cir. 1992). In some circumstances, however, “the Due Pro-
cess Clause requires dismissal of an indictment brought
within the [statute of] limitations period.” Id.

   [2] We review for abuse of discretion a district court’s
denial of a motion to dismiss for pre-indictment delay under
the Fifth Amendment’s Due Process Clause. United States v.
Barken, 412 F.3d 1131, 1134 (9th Cir. 2005). In order to suc-
ceed on his claim that he was denied due process because of
pre-indictment delay, Corona-Verbera must satisfy both
prongs of a two-part test. First, he must prove “actual, non-
speculative prejudice from the delay.” Huntley, 976 F.2d at
1290. Second, the length of the delay is weighed against the
reasons for the delay, and Corona-Verbera must show that the
delay “offends those ‘fundamental conceptions of justice
               UNITED STATES v. CORONA-VERBERA             16047
which lie at the base of our civil and political institutions.’ ”
Sherlock, 962 F.2d at 1353 54 (quoting United States v.
Lovasco, 431 U.S. 783, 790 (1977)). The second prong of the
test applies only if Corona-Verbera has demonstrated actual
prejudice. Barken, 412 F.3d at 1136. We have held that estab-
lishing prejudice is a “heavy burden” that is rarely met. Hunt-
ley, 976 F.2d at 1290. “Generalized assertions of the loss of
memory, witnesses, or evidence are insufficient to establish
actual prejudice.” United States v. Manning, 56 F.3d 1188,
1194 (9th Cir. 1995). Consequently, Corona-Verbera must
show both that lost testimony, witnesses, or evidence “mean-
ingfully has impaired his ability to defend himself,” and “[t]he
proof must demonstrate by definite and non-speculative evi-
dence how the loss of a witness or evidence is prejudicial to
[his] case.” Huntley, 976 F.2d at 1290.

   Corona-Verbera argues that he suffered actual prejudice
because the delay prevented him from: 1) tracking down wit-
nesses or calling witnesses who died after the indictment to
support his “mere presence” defense; 2) locating architectural
plans showing what he was constructing in Agua Prieta; 3)
producing destroyed financial records documenting his lawful
earnings; and 4) having his expert examine the physical evi-
dence that was not preserved, including the tunnel itself and
a drain grate Corona-Verbera allegedly purchased.

  [3] With respect to lost witnesses, Corona-Verbera’s claim
of prejudice fails for two reasons. First, the indictment was
brought within the five-year statute of limitations. We have
held that, generally, protection from lost testimony “falls
solely within the ambit of the statute of limitations.” Sherlock,
962 F.2d at 1354 (citations omitted).

   [4] Second, Corona-Verbera’s arguments are based on gen-
eralized speculation as to what lost or deceased witnesses
would have said. He offers no affidavits nor any non-
speculative proof as to how he was prejudiced by the loss of
his witnesses. In Sherlock, we found no prejudice where the
16048          UNITED STATES v. CORONA-VERBERA
record did not indicate how witnesses “would have testified
had their memories not dimmed.” Id. Similarly, when a defen-
dant fails to make a specific showing as to what a deceased
witness would have said, any argument of prejudice is pure
conjecture. Manning, 56 F.3d at 1194. Furthermore, allega-
tions of prejudice “must be supported by non-speculative
proof.” United States v. Doe, 149 F.3d 945, 949 (9th Cir.
1998). Consequently, Corona-Verbera has not established that
the loss of potential witnesses constituted a meaningful
impairment to his ability to defend himself.

   Similarly, the mere absence of records is not enough to
establish actual prejudice. Manning, 56 F.3d at 1194. In Man-
ning, we declined to find prejudice when the defendant argued
that the loss of access to credit card records could have
explained his location at the time of the crime. Id. Corona-
Verbera’s argument that financial or architectural records
would have established lawful income and work is not persua-
sive. Financial records could establish lawful earnings, but the
mere existence of such records would not necessarily estab-
lish that Corona-Verbera had no unlawful income. Similarly,
the existence of architectural plans showing construction of a
legitimate residence would not be persuasive evidence estab-
lishing Corona-Verbera’s innocence. Anyone designing an
illegal drug tunnel would be unlikely to include drawings of
such a tunnel on plans submitted to a government agency.

   [5] Corona-Verbera’s preservation of evidence argument
stemming from the destruction of the tunnel is also not per-
suasive. “[W]here adequate substitutes exist for missing non-
testimonial evidence, prejudice does not exist.” Barken, 412
F.3d at 1135. Corona-Verbera has not established that the lack
of preservation of the tunnel and the grate caused actual, sub-
stantial prejudice. His only argument is that his expert did not
have an opportunity to examine them. This argument fails
because the record contains numerous descriptions and photo-
graphs of the tunnel and the grate, and Corona-Verbera’s
claim that the pictures were inadequate is not convincing.
                UNITED STATES v. CORONA-VERBERA                  16049
   [6] We hold that the district court did not abuse its discre-
tion in denying Corona-Verbera’s motion to dismiss.2

  B.    Federal Rule of Criminal Procedure 48(b)

   We review for abuse of discretion the denial of a motion to
dismiss for pre-indictment delay under Federal Rule of Crimi-
nal Procedure 48(b). Id. at 1134. The district court denied
Corona-Verbera’s motion because there was no suggestion of
purposeful or oppressive delay. See United States v. Talbot,
51 F.3d 183, 187 (9th Cir. 1995). However, we affirm the dis-
trict court on different grounds: Rule 48(b) “clearly is limited
to post-arrest situations.” United States v. Marion, 404 U.S.
307, 319 (1971); see also Barken, 412 F.3d at 1136 (“Rule
48(b) comes into play only after a defendant has been placed
under arrest.”). Corona-Verbera’s reliance on this rule to sup-
port his claim of unlawful pre-trial delay is misplaced.

  C.    Speedy Trial

   [7] The Sixth Amendment guarantees that “[i]n all criminal
prosecutions, the accused shall enjoy the right to a speedy and
public trial.” U.S. CONST. amend. VI. Once the accused
demands a speedy trial, the government must “make a ‘dili-
gent, good-faith effort’ to bring the accused before the court
for trial.” United States v. Sandoval, 990 F.2d 481, 484 (9th
Cir. 1993) (quoting Smith v. Hooey, 393 U.S. 374, 383
(1969)).

  We review de novo the district court’s resolution of a claim
under the Sixth Amendment’s Speedy Trial Clause, but we
will not overturn the district court’s subsidiary factual find-
  2
    Although we need not address the reasons for the delay because
Corona-Verbera has not demonstrated actual prejudice, Barken, 412 F.3d
at 1136, we note that he has failed to show that the delay was caused by
the government attempting “to gain tactical advantage” over him. Sher-
lock, 962 F.2d at 1354 (quoting Lovasco, 431 U.S. at 795).
16050          UNITED STATES v. CORONA-VERBERA
ings unless they are clearly erroneous. United States v. Greg-
ory, 322 F.3d 1157, 1160 (9th Cir. 2003).

   We assess the merits of Corona-Verbera’s “claimed viola-
tion of the Sixth Amendment speedy trial right by applying a
balancing test involving four factors: (1) the length of the
delay; (2) the reason for the delay; (3) the defendant’s asser-
tion of his right to a speedy trial; and (4) the prejudice to the
defendant.” Id. at 1161 (citing Barker v. Wingo, 407 U.S. 514,
530 (1972)).

    1.   Length of Delay

   [8] “The length of the delay is to some extent a triggering
mechanism.” Barker, 407 U.S. at 530. Most courts have found
a delay that approaches one year is presumptively prejudicial.
Gregory, 322 F.3d at 1161-62. We hold that the nearly eight-
year delay between indictment and arrest is presumptively
prejudicial and sufficient to trigger inquiry into the other three
factors.

    2.   Reason for Delay

   [9] We next address the reason for the delay. Whether or
not our government is required formally to seek extradition
and execute an arrest warrant when it believes extradition is
futile is an issue of first impression in this Circuit. The Sec-
ond Circuit addressed the issue in United States v. Blanco,
861 F.2d 773, 778 (2d Cir. 1988). In Blanco, the court held
that seeking extradition of a defendant from Colombia would
have been futile and “[d]ue diligence does not require the
government to pursue goals that are futile.” Id. We agree with
the Second Circuit and hold that where our government has
a good faith belief supported by substantial evidence that
seeking extradition from a foreign country would be futile,
due diligence does not require our government to do so.

  In this case, the trial court found that:
               UNITED STATES v. CORONA-VERBERA            16051
    [T]he Government . . . presented evidence through
    the testimony of Agent Grant Murray, which was not
    refuted by Defendant’s expert, that Mexico was not
    extraditing Mexican citizens on narcotics charges
    until the late 1990s, and while the Government did
    not cease its efforts to locate and arrest the Defen-
    dant, any efforts by the Government to extradite the
    Defendant earlier would have been futile.

   [10] Agent Grant Murray testified that Corona-Verbera’s
name was put into the National Crime Information Center
(“NCIC”) computer system in 1990. Entries were kept also in
the border computer system. When the 1995 superceding
indictment was returned, that information was entered also
into NCIC and the border computer system. These actions
constitute diligence on the part of the government. See United
States v. Aguirre, 994 F.2d 1454, 1455-57 (9th Cir. 1993)
(upholding district court’s finding that the government was
diligent when the only action agents took was entering
“stops” on defendant).

   [11] In an attempt to locate Corona-Verbera and execute
the arrest warrant by enlisting the help of the public, the gov-
ernment contacted Unsolved Mysteries and America’s Most
Wanted. Unsolved Mysteries aired a segment in the United
States on the Douglas Tunnel twenty times between 1991 and
1997 and at least once in Mexico in 2000 or 2001. America’s
Most Wanted aired a segment on the Douglas Tunnel in 1996.
The Unsolved Mysteries program contains a mug shot and
narration regarding Corona-Verbera. Agent Murray testified
Corona-Verbera’s name was mentioned in both documenta-
ries.

   [12] Furthermore, the government offered testimony that it
believed that seeking extradition of a Mexican national on
drug charges during the 1990s would have been futile. This
belief was backed by substantial evidence. Agent Murray tes-
tified that he contacted an Assistant United States Attorney
16052          UNITED STATES v. CORONA-VERBERA
(“AUSA”) seeking a provisional warrant for Corona-Verbera,
and that the AUSA informed him “the Mexican government
was not extraditing nationals back to the United States.” An
expert for the defense agreed that from 1980 to 1996 no Mex-
ican nationals were extradited to the United States. Finally, a
United States Department of State (“DOS”) report admitted at
the motion hearing supports the government’s assertion that
extradition would have been futile. With respect to extradition
from Mexico to the United States on drug charges, the report
indicates that one Mexican national was extradited both in
1999 and 2000; eleven people were extradited in 2001; and
seventeen people were extradited in 2002. Corona-Verbera
was extradited in 2003 after Agent Murray received a tip in
October of 2002 and obtained a provisional arrest warrant and
an extradition. The DOS report supports the government’s
belief that very few people were extradited on drug charges
from Mexico to the United States before 2002, the year when
the government found Corona-Verbera. Consequently, if the
government was not able to extradite Corona-Verbera, it also
could not execute the arrest warrant.

   Corona-Verbera argues that this case is like Doggett v.
United States, 505 U.S. 647 (1992). On its facts, Doggett is
distinguishable. In that case, the district court found the gov-
ernment’s actions were negligent. The Supreme Court
accepted the district court’s determination of negligence
which it reviewed “with considerable deference.” Id. at 652.
In Corona-Verbera’s case, the district court did not find that
the government was negligent, to the contrary.

   [13] We conclude, as did the district court, that the govern-
ment exercised due diligence in this case. Substantial evi-
dence supports the government’s assertion that extradition
from Mexico on drug related charges prior to 2002 was
extremely rare. The futility of extradition, combined with the
government’s entry of Corona-Verbera into NCIC and border
stop computers, and the airing of the Most Wanted and
Unsolved Mysteries segments, indicate that the government
               UNITED STATES v. CORONA-VERBERA             16053
did not simply forget about Corona-Verbera. Rather, after
extradition became more likely in 2002, the government
obtained an arrest warrant and diligently sought extradition.
Consequently, the reason for delay weighs against dismissal.

    3.   Assertion of Right to Speedy Trial

   [14] Corona-Verbera asserted his right to a speedy trial
only after he had asked for eight continuances, including one
request after objecting to a continuance requested by the gov-
ernment. Because Corona-Verbera asserted his speedy trial
right only after requesting numerous continuances, we find
this factor weighs neither in favor of dismissal nor in favor of
the government.

    4.   Prejudice to Corona-Verbera

   The remaining factor is prejudice. We have already con-
cluded that the nearly eight-year delay between the indictment
and arrest is presumptively prejudicial. “While such presump-
tive prejudice cannot alone carry a Sixth Amendment claim
without regard to the other Barker criteria, it is part of the mix
of relevant facts, and its importance increases with the length
of delay.” Doggett, 505 U.S. at 655-56 (internal citations
omitted). Therefore, we must “weigh the reasons for and the
extent of the delay against the evidence of actual prejudice.”
United States v. Beamon, 992 F.2d 1009, 1013 (9th Cir. 1993)
(citing Doggett, 505 U.S. at 656). If the government pursued
Corona-Verbera “with reasonable diligence from his indict-
ment to his arrest, his speedy trial claim would fail” unless
Corona-Verbera can show “specific prejudice to his defense.”
Doggett, 505 U.S. at 656.

  [15] Corona-Verbera argues that under Doggett, he does
not need to show specific prejudice because the government
was negligent in pursuing him. We disagree. The district court
found, and we agree, that the government’s actions in pursu-
16054             UNITED STATES v. CORONA-VERBERA
ing Corona-Verbera were diligent.3 Consequently, Corona-
Verbera is required to demonstrate specific prejudice; preju-
dice is not presumed. See id. at 656; Manning, 56 F.3d at
1194.

   [16] One of the three traditional ways to show prejudice is
by demonstrating that the defense was impaired. Doggett, 505
U.S. at 654. Corona-Verbera’s arguments for prejudice here
are the same as those he raised in his due process claim. We
concluded above that Corona-Verbera has not demonstrated
actual prejudice. We concluded also that the eight-year delay
between the indictment and the arrest was due only to the
futility of seeking extradition from Mexico of a Mexican
national on drug charges. On balance, this factor weighs
against dismissal because the government pursued Corona-
Verbera with reasonable diligence, and, again, he has not
demonstrated specific prejudice.

   [17] Although the nearly eight-year delay from the time of
the indictment to the time of arrest was lengthy, balancing the
Barker factors, dismissal is not warranted. We therefore hold
there was no violation of Corona-Verbera’s Sixth Amendment
speedy trial right.

  D.    Insufficiency of the Evidence

   We review de novo claims of insufficient evidence. United
States v. Stanton, 501 F.3d 1093, 1099 (9th Cir. 2007). “There
is sufficient evidence to support a conviction if, ‘viewing the
evidence in the light most favorable to the prosecution, any
rational trier of fact could have found the essential elements
  3
    Because we agree that the government was diligent, we do not find
United States v. Shell, 974 F.2d 1035 (9th Cir. 1992), persuasive. In that
case, we upheld the dismissal of an indictment based on a five-year delay
between indictment and arrest. Unlike the present case, in Shell, the delay
was caused by the government’s negligent misplacement of the prosecu-
tion file, and therefore the appellant was not required to show actual preju-
dice. Id. at 1036.
               UNITED STATES v. CORONA-VERBERA             16055
of the crime beyond a reasonable doubt.’ ” United States v.
Deeb, 175 F.3d 1163, 1168 (9th Cir. 1999) (quoting Jackson
v. Virginia, 443 U.S. 307, 319 (1979)). Conflicting evidence
is to be resolved in favor of the jury verdict, and “all reason-
able inferences are to be drawn in favor of the government.”
United States v. Alvarez-Valenzuela, 231 F.3d 1198, 1201-02
(9th Cir. 2000).

    1.   Counts 1 and 2

    [18] The jury found Corona-Verbera guilty of conspiracy to
import cocaine and conspiracy to possess with intent to dis-
tribute marijuana and cocaine. Corona-Verbera and the gov-
ernment both agree that a conspiracy existed. “Once the
existence of a conspiracy is established, evidence which
establishes beyond a reasonable doubt that a defendant is even
slightly connected with the conspiracy is sufficient to convict
. . . .” United States v. Boone, 951 F.2d 1526, 1543 (9th Cir.
1991). A defendant may be “slightly connected” even if he
did not know all the conspirators, did not know all the details
of the conspiracy, did not participate in the conspiracy from
the outset, and did not participate in all the enterprises of the
conspiracy. See United States v. Herrera-Gonzalez, 263 F.3d
1092, 1095 (9th Cir. 2001). Additionally, circumstantial evi-
dence that the defendants acted with a common goal is suffi-
cient also to prove agreement, and agreement may be inferred
from conduct, express agreement is not necessary. United
States v. Hegwood, 977 F.2d 492, 497 (9th Cir. 1992).

  Corona-Verbera argues that he was “merely present” and
had no knowledge of this conspiracy. Therefore, we must
determine whether there is sufficient evidence to tie Corona-
Verbera to the criminal activities. Herrera-Gonzalez, 263
F.3d at 1095. We have explained that “[t]he mere presence of
a defendant in suspicious circumstances is not enough to
imply knowledge.” Hegwood, 977 F.2d at 498. Additionally,
mere presence “at the location of a conspiracy’s activities,
while the activities are taking place, knowing that they are
16056         UNITED STATES v. CORONA-VERBERA
taking place, without proof of intentional participation in the
conspiracy, cannot support a conspiracy conviction.”
Herrera-Gonazalez, 263 F.3d at 1097.

   [19] Here, there was sufficient evidence for a reasonable
juror to find that Corona-Verbera intentionally participated in
the conspiracy and was more than “merely present” at both
the ingress and egress of the tunnel. Corona-Verbera was an
active participant in the construction of both Camarena’s resi-
dence and the warehouse. Various witnesses identified
Corona-Verbera as the architect at both sites, reflecting that
he was more than “merely present.” Thus, a reasonable juror
could have concluded that Corona-Verbera had control over
both sites as the architect.

   Further, although Corona-Verbera denies any knowledge of
the drug conspiracy and consequently the tunnel, there is con-
siderable evidence to the contrary. Jesus Garcia (“Garcia”), a
contractor and roofer working on the Camarena home, testi-
fied that “Corona was the architect for the whole project.”
During construction of the Camarena home, there was a four-
foot hole filled with sand and gravel where the recreation
room at the Camarena house was supposed to be. Garcia was
told by an unknown person that the hole was eventually going
to be an Olympic sized swimming pool. However, when
agents discovered the tunnel, there was no swimming pool,
instead there was a tunnel, accessed through the recreation
room of the Camarena home. A reasonable juror could have
concluded the swimming pool story was a cover, and that as
the architect for the residence, Corona-Verbera perpetuated
that story to hide the fact that the hole was actually the
entrance to the tunnel.

   Lomeli, Woods, and Romero testified that Corona-Verbera
told them the purpose of the warehouse was to wash trucks.
However, there was no plumbing or water in the warehouse.
Lomeli and Romero testified also that the drainage grates that
concealed the tunnel’s egress were too high for water to drain.
              UNITED STATES v. CORONA-VERBERA            16057
Lomeli and Woods testified further that Corona-Verbera had
them rip out otherwise functional two-by-two drains that had
been installed at the warehouse and replace them with two-
by-four drains, regardless of the cost. The two-by-four drains
covered the access to the tunnel. A reasonable juror could
have concluded from this testimony that Corona-Verbera
knew that the warehouse was not designed to wash trucks,
and that his orders to tear out the drains indicated he knew
that the drains were not large enough to bring drugs out of the
tunnel.

   The tunnel entrance at the Camarena’s home was opened
by activating a hydraulic system. Romero testified he deliv-
ered pistons “like a hydraulic lift,” to Corona-Verbera and
Camarena. Martinez testified that in the past, Corona-Verbera
built or repaired other structures for El Chappo equipped with
hydraulic systems concealing hidden “clavos.” Several ware-
houses and complexes owned by El Chappo had similar
devices in the floor that hid underground rooms. Martinez tes-
tified that El Chappo said he asked Corona-Verbera to build
the tunnel. Martinez further testified that Corona-Verbera and
El Chappo were close enough acquaintances that Corona-
Verbera referred to El Chappo with the familiar “tu” instead
of the formal “usted.” If the jury believed Martinez and
Romero, it reasonably could have concluded that Corona-
Verbera designed the tunnel using hydraulic lifts similar to
former designs for El Chappo, that Corona-Verbera had a
close relationship with El Chappo, and that Corona-Verbera
knew the tunnel he designed was going to be used for smug-
gling drugs.

   Corona-Verbera argues that Martinez’s “uncorroborated”
testimony is the only testimony linking Corona-Verbera to the
conspiracy. During the trial, Corona-Verbera’s attorney exten-
sively questioned Martinez about his prior conflicting testi-
mony, and the jury heard it all. A reasonable juror could have
accepted some parts of Martinez’s testimony as true and
rejected others. See United States v. Heredia, 483 F.3d 913,
16058         UNITED STATES v. CORONA-VERBERA
923 n.14 (9th Cir. 2007) (en banc). Additionally, much of
Martinez’s testimony was corroborated in part by circumstan-
tial evidence and other witnesses including Corona-Verbera’s
friend, Woods.

   [20] Taken together, viewed in the light most favorable to
the prosecution, we hold there was enough evidence for a rea-
sonable juror to find Corona-Verbera was more than “merely
present,” and he intentionally participated in the conspiracy.
We affirm as to counts 1 and 2.

    2.   Counts 19 and 20

   [21] Counts 19 and 20 relate to the seizure of the cocaine
from Queen Creek on May 11, 1990. Three legal theories can
support a conviction for possession with intent to distribute:
aiding and abetting, co-conspirator liability, and dominion
and control. United States v. Ramirez-Robles, 386 F.3d 1234,
1240 (9th Cir. 2004). We hold there is sufficient evidence to
uphold Corona-Verbera’s conviction as an aider and abetter.

   A conviction for aiding and abetting requires the govern-
ment to prove that Corona-Verbera associated himself with
the venture, “that he participate[d] in it as in something that
he wishe[d] to bring about, [and] that he [sought] by his
action to make it succeed.” Id. at 1241. A conviction may not
be upheld based on “mere casual association with conspiring
people.” Id. (internal quotation marks omitted). Circumstan-
tial evidence may support a conviction as an aider and abetter.
Id.

   [22] We have concluded from the record that a reasonable
juror could have found that Corona-Verbera participated in an
international drug conspiracy when he designed the Douglas
Tunnel. The purpose of the tunnel was to bring drugs into the
United States from Mexico. Thus, Corona-Verbera partici-
pated in a venture that he wished to bring about, and in
designing the tunnel, he sought to make the venture succeed.
               UNITED STATES v. CORONA-VERBERA            16059
   [23] There was also sufficient circumstantial evidence that
the drugs seized at Queen Creek were imported into the
United States through the tunnel and transported to Queen
Creek in the flatbed truck followed by government agents.
Agents followed the flatbed truck from the Douglas Ware-
house located at the tunnel egress. Agents testified they
observed flashes of light from the Queen Creek Complex and
later discovered that the truck they followed from the ware-
house had a hidden compartment, which was opened with a
welding torch. In fact, when they found the truck, the hidden
compartment was exposed and the false bed laid over the top
of it. Martinez testified that El Chappo told him a large ship-
ment of drugs had been seized by the United States after the
drugs had been brought into the United States through the tun-
nel. A reasonable juror could have concluded, based on the
testimony of law enforcement and Martinez, that the drugs
located at Queen Creek were imported from Mexico into the
United States through the tunnel; that the drugs were loaded
into the flatbed truck at the warehouse; and that the flashes of
light observed by agents were the false bed being removed so
the drugs could be taken from the flatbed truck.

   [24] Furthermore, around the same time the drugs were
seized, Corona-Verbera and his family disappeared from their
trailer in Douglas, and the school records for Corona-
Verbera’s children show they were absent beginning on May
11, 1990, the day the cocaine was seized. A reasonable juror
could have concluded Corona-Verbera knew that the seized
cocaine was transported through the tunnel and knew also that
he was in danger of being arrested for his involvement in
importing drugs. Viewed in the light most favorable to the
prosecution, a reasonable juror could have found Corona-
Verbera guilty on counts 19 and 20, and we so hold.

  E.   Sentencing

  After United States v. Booker, 543 U.S. 220 (2005), we no
longer review sentences imposed by a district court de novo.
16060           UNITED STATES v. CORONA-VERBERA
Booker replaced the de novo standard of review “with an
abuse-of-discretion standard that we called ‘reasonable-
ness.’ ” Rita v. United States, 127 S. Ct. 2456, 2470 (2007)
(Stevens, J., concurring). We review for clear error the district
court’s factual findings. United States v. Kimbrew, 406 F.3d
1149, 1151 (9th Cir. 2005). Finally, we review for abuse of
discretion a district court’s determination that a defendant’s
particular abilities constitute a “special skill” because it is an
application of law to the facts. Id. at 1151; United States v.
Lee, 296 F.3d 792, 795 (9th Cir. 2002).

   Corona-Verbera raises three arguments regarding his four
concurrent eighteen-year sentences: 1) the sentence was
grossly disproportionate to the sentences imposed on co-
conspirators Martinez and Camarena; 2) the district court’s
factual findings that he used his special skill as an architect
to facilitate the crimes were erroneous because there is no evi-
dence that Corona-Verbera used his skills as an architect; and
3) an eighteen-year sentence is tantamount to a life sentence,
in violation of the United States-Mexico Extradition Treaty
and the terms of the extradition agreement. We disagree.

  1.    Sentence Disparity

   Corona-Verbera argues that his sentence was grossly dis-
proportionate to those of his co-conspirators, Camarena and
Martinez. Unlike Corona-Verbera, Camarena entered a guilty
plea and accepted responsibility. He was sentenced to ten
years. Likewise, Martinez entered a guilty plea, accepted
responsibility, and agreed to cooperate with the government
and testify against his co-conspirators. He was sentenced to
eighteen years.

   We assess whether the ultimate sentence is reasonable in
light of the factors in 18 U.S.C. § 3553(a). United States v.
Nichols, 464 F.3d 1117, 1124 (9th Cir. 2006).

       To comply with the requirements of Booker, the dis-
       trict court must have sufficiently considered the
                 UNITED STATES v. CORONA-VERBERA            16061
       Guidelines as well as the other factors listed in
       § 3553(a). This requirement does not necessitate a
       specific articulation of each factor separately, but
       rather a showing that the district court considered the
       statutorily-designated factors in imposing a sentence.

United States v. Knows His Gun, 438 F.3d 913, 918 (9th Cir.
2006). “[T]he need to avoid unwarranted sentencing dispari-
ties is only one factor a district court is to consider in impos-
ing a sentence.” United States v. Marcial-Santiago, 447 F.3d
715, 719 (9th Cir. 2006).

   [25] Corona-Verbera has not demonstrated that the district
court overlooked any of these factors. Furthermore, the dis-
trict court considered at length the disparity between Corona-
Verbera’s sentence and those of his co-conspirators. The court
found that the disparity warranted a variance “substantially
below the advisory guideline.” Consequently, the court
imposed a sentence seventy-six months below the applicable
Guideline range. We hold that the disparity in sentencing here
was not so disproportionate as to render the eighteen-year
sentence unreasonable.

  2.     Special Skills Enhancement

   The Sentencing Guidelines allow a district court judge to
impose a two-level sentence enhancement if the defendant
“used a special skill, in a manner that significantly facilitated
the commission or concealment of the offense.” U.S.S.G.
§ 3B1.3. A “special skill” is “a skill not possessed by mem-
bers of the general public and usually requiring substantial
education, training or licensing. Examples would include
pilots, lawyers, doctors, accountants, chemists, and demoli-
tion experts.” U.S.S.G. § 3B1.3. cmt. 4.

   We apply a two-part test to determine whether or not a skill
constitutes a “special skill” within the meaning of the guide-
lines. Lee, 296 F.3d at 798. First, we determine whether the
16062          UNITED STATES v. CORONA-VERBERA
skill is possessed by members of the general public. Id. Sec-
ond, we determine whether the skill requires substantial train-
ing, education or licensing, and is analogous to the skills
described in the application note. Id. at 798-99. We have held
that cheating at cards does not constitute a special skill
because it is useless outside the criminal context. United
States v. Liang, 362 F.3d 1200, 1203 (9th Cir. 2004). We have
held also that driving an eighteen-wheeler without mishap
over a period of several years does constitute a special skill
because it is a skill well beyond that possessed by the general
public. United States v. Mendoza, 78 F.3d 460, 465 (9th Cir.
1996).

   [26] Corona-Verbera was an architect. This is a legitimate
skill outside of the criminal context, and it is not a skill pos-
sessed by the general public. The district court found, based
on the jury verdict, that because of his skills as an architect,
Corona-Verbera was hired to build the Douglas Tunnel, the
Camarena home, and the Douglas Warehouse. This finding
was not clearly erroneous, nor was the application of these
facts to the law an abuse of discretion in light of the evidence
presented at trial that the tunnel was highly sophisticated. The
tunnel was lined with concrete; accessed with a hidden
hydraulic system; and equipped with electricity, a pulley sys-
tem like that of an elevator, an air compressor system, and
tubular piping used to drain the tunnel of water. Furthermore,
because all require substantial education, the skill of an archi-
tect is analogous to those of pilots, lawyers, doctors, accoun-
tants, and demolition experts. We affirm the special skills
enhancement.

  3.    Extradition Agreement and Treaty Violation

  The specific agreement between the United States and
Mexico to extradite Corona-Verbera contains a binding assur-
ance from our Ambassador to Mexico that the United States
will neither seek nor impose a death sentence or life imprison-
ment. Predicated upon this assurance, Corona-Verbera argues
               UNITED STATES v. CORONA-VERBERA            16063
that because he is fifty-three years old, his eighteen-year sen-
tence is “tantamount to a life sentence” in violation of the
terms of his extradition. He intermingles with this argument
an assertion that a life sentence constitutes “cruel and extreme
punishment,” and that Articles 18 and 22 of the Mexican Con-
stitution prohibit the imposition of punishment that can be so
characterized. He argues also that because a life sentence con-
stitutes cruel and extreme punishment, it violates the United
States-Mexico Extradition Treaty. Corona-Verbera attempts
to support these arguments with a decision of the Supreme
Court of Mexico holding that Mexico will not extradite sus-
pects facing a life sentence on the ground that life imprison-
ment constitutes “unusual or extreme punishment.” See
Rodrigo Labardine, Life Imprisonment and Extradition: His-
torical Development, International Context, and the Current
Situation in Mexico and the United States, 11 Sw. J. L. &
Trade Am. 1, 52 (2005). We find these inventive arguments
not convincing.

   [27] Neither our Ambassador’s letter nor the Treaty itself
mention any prohibition against a sentence imposing a precise
term of years. Likewise, no mention is made of “unusual or
extreme punishment” or any equivalent thereof. See Extradi-
tion Treaty Between the United States of America and the
United Mexican States, U.S.-Mex., May 4, 1978, 31 U.S.T.
5059. Accordingly, the simple answer to Corona-Verbera’s
argument is that he was not sentenced to life in prison. He
was sentenced to eighteen years in prison, with credit for
more than four years served. Moreover, his projected release
date is at the age of sixty-four.

                              III

                       CONCLUSION

   Corona-Verbera has not demonstrated actual prejudice with
respect to his claims of unlawful delay. The government was
diligent in its efforts to bring Corona-Verbera to trial and was
16064         UNITED STATES v. CORONA-VERBERA
not required to seek extradition from Mexico when it believed
extradition was futile. Therefore, Corona-Verbera’s Sixth
Amendment claim fails. There was sufficient evidence for a
reasonable juror to convict Corona-Verbera on counts 1, 2,
19, and 20. Finally, the eighteen-year sentence was reasonable
and did not violate any treaty obligations or the terms of the
extradition agreement.

  AFFIRMED
