                       PUBLISHED


UNITED STATES COURT OF APPEALS
             FOR THE FOURTH CIRCUIT


UNITED STATES OF AMERICA,             
               Plaintiff-Appellant,
               v.                         No. 10-4417
STEPHEN GERARD DIGIOVANNI,
              Defendant-Appellee.
                                      
       Appeal from the United States District Court
        for the District of Maryland, at Baltimore.
            Catherine C. Blake, District Judge.
                 (1:09-cr-00421-CCB-1)

                  Argued: May 12, 2011

                  Decided: July 25, 2011

         Before MOTZ and DIAZ, Circuit Judges,
          and HAMILTON, Senior Circuit Judge.



Affirmed by published opinion. Senior Judge Hamilton wrote
the opinion in which Judge Motz and Judge Diaz joined.


                        COUNSEL

ARGUED: Ayn Brigoli Ducao, OFFICE OF THE UNITED
STATES ATTORNEY, Baltimore, Maryland, for Appellant.
Marta Kahn, Baltimore, Maryland, for Appellee. ON BRIEF:
Rod J. Rosenstein, United States Attorney, Baltimore, Mary-
2                   UNITED STATES v. DIGIOVANNI
land, for Appellant. William B. Purpura, PURPURA & PUR-
PURA, Baltimore, Maryland, for Appellee.


                             OPINION

HAMILTON, Senior Circuit Judge:

  The United States appeals from an order of the district
court granting the motion to suppress certain evidence filed
by the defendant, Stephen Digiovanni. We affirm.

                                   I

   On July 28, 2009, at approximately 11:53:00 a.m., Trooper
Christopher Conner of the Maryland State Police observed
Digiovanni’s car traveling northbound on Interstate 95 (I-95),
in northeast Maryland, near the towns of North East and Per-
ryville. In Trooper Conner’s opinion, Digiovanni’s car was
traveling too close to the car in front of him, in violation of
Maryland law. Consequently, Trooper Conner activated his
patrol car’s blue lights (which in turn activated his patrol car’s
video and recording equipment) and effectuated a stop of
Digiovanni’s car.

   At approximately 11:53:39 a.m., Trooper Conner
approached Digiovanni’s car, now stopped on the right shoul-
der of the road, identified himself as a Maryland state trooper,
and asked Digiovanni to provide his driver’s license and the
car’s registration, explaining to Digiovanni that he was fol-
lowing the car in front of him "entirely too close." In
response, Digiovanni, who was the sole occupant of the car,
indicated that the car he was driving was a rental car, so he
provided the rental contract, along with his Massachusetts
driver’s license. As Digiovanni handed over these items,
Trooper Conner directed him to exit the car, which he did.1
    1
    As the requested items were passed, Trooper Conner noticed Digiovan-
ni’s hands were trembling.
                     UNITED STATES v. DIGIOVANNI                         3
Such direction occurred at approximately 11:54:09 a.m., or
about thirty seconds after Trooper Conner first approached
Digiovanni’s car. According to Trooper Conner, he asked
Digiovanni to exit the car for the purpose of issuing him a
warning ticket and for the purpose of determining whether
there was criminal activity afoot.2

   While collecting Digiovanni’s driver’s license and the
rental contract, Trooper Conner noticed two shirts hanging in
the rear passenger compartment and a hygiene bag on the
back seat. He also noticed the interior of the car was clean. At
the suppression hearing, Trooper Conner testified that the
hanging shirts suggested Digiovanni may be involved in drug
trafficking activity, because, through his experience, non-drug
traffickers traveling on vacation would have such items
packed in a clothing bag. Trooper Conner also testified that
the hygiene bag on the back seat was suggestive of drug traf-
ficking activity, because there was no other visible luggage in
the car. As for the clean condition of the interior of the car,
Trooper Conner indicated this was suggestive of drug traffick-
ing activity, because "[t]here was nothing in the vehicle indi-
cating that [he was] living on the road, nonstop driving."

   At the suppression hearing, Trooper Conner testified that
the rental contract also made him suspicious of drug traffick-
ing activity. The rental contract indicated that the car was
rented at Fort Lauderdale International Airport the previous
day and was to be dropped off at Logan International Airport
in Boston, at a cost of $438. Trooper Conner testified that
Digiovanni’s one-way, $438 car rental was "implausible."

   After Digiovanni exited the car, he walked to the rear of the
  2
     Trooper Conner is a member of the Pro-Active Criminal Enforcement
Team (PACE), a Maryland State Police task force that focuses on criminal
traffic enforcement on Maryland roadways to identify drug, criminal, and
terrorist organizations that use motor vehicles in the furtherance of their
illicit activities.
4                   UNITED STATES v. DIGIOVANNI
car, positioning himself near the guardrail. Trooper Conner
then retrieved his warning book from his patrol car and
returned to where Digiovanni was standing. At this point,
Trooper Conner asked numerous questions concerning
Digiovanni’s travel history and travel plans. All parties seem
to acknowledge that perhaps three of these questions related
to the justification for the stop, in that, based on his answers,
Digiovanni may have offered an explanation for driving too
close to the car in front of him. In response to this question-
ing, Digiovanni indicated that: (1) he was traveling from Flor-
ida, where he spent the weekend with family, to Boston,
where he lived; (2) on his way to Boston, he was stopping at
his sister’s residence in New York to pick up "some paintings
and whatnot"; and (3) he took the Amtrak Auto Train from
Florida to Virginia.

   At about 11:56:40, or a little more than three minutes into
the stop, Trooper Conner turned his questioning to the subject
of drug trafficking activity, because, in his opinion, he had
reasonable suspicion that criminal activity was afoot. He
asked Digiovanni if he had any luggage in the car and if
everything in the car belonged to him. Digiovanni responded
in the affirmative to both questions. After these two questions,
Digiovanni said, "oh boy," as he tossed the cigarette he was
smoking over the guardrail. At the suppression hearing,
Trooper Conner testified that he found this remark "extremely
suspicious," because "now he is saying oh boy in response to
my questioning." Trooper Conner then asked Digiovanni what
was the matter, to which Digiovanni replied, "[i]t’s just so
hot." Trooper Conner explained to Digiovanni that people
smuggle drugs and guns up and down I-95, and that "a lot of
good people . . . agree to take a box or something . . . [that]
[t]hey really don’t know what’s in it." Trooper Conner told
Digiovanni that he was not accusing him of anything, but that
he "had a job to do out here." He asked Digiovanni if there
was any marijuana in the car. Digiovanni replied, "[n]o sir. I
never smoked marijuana in my life. It puts me to sleep."3
    3
    Trooper Conner found Digiovanni’s nonsensical answer to his mari-
juana question "extremely suspicious," because "if you never have smoked
it, you wouldn’t know that it makes you sleepy."
                  UNITED STATES v. DIGIOVANNI                  5
Trooper Conner asked Digiovanni if there was any cocaine or
heroin in the car, and Digiovanni responded in the negative.
Trooper Conner also asked Digiovanni if there was any
methamphetamine in the car, and Digiovanni indicated that
there was not. Trooper Conner followed up with, "[a]re you
sure?," to which Digiovanni replied, "I’m positive."

   At the conclusion of approximately one minute and thirty-
five seconds of questioning concerning drug trafficking activ-
ity, Trooper Conner turned his questioning to the subject of
consent. Just before asking Digiovanni for consent to search
the car, Trooper Conner told Digiovanni that he routinely
searches cars "to make sure there’s no drugs or guns" in them.
In response to his request to search the car, Digiovanni
replied, at 11:58:24 a.m., "[i]f you want to, that’s not a prob-
lem."

    For the next three minutes or so, Digiovanni attempted to
open the trunk of the car to allow Trooper Conner to search
it, but he could not open it. According to Trooper Conner, he
found this "extremely suspicious," because Digiovanni, at
some earlier time, was able to load his luggage in the trunk.
He also testified that, in his experience, drug traffickers often
disable the mechanism for opening the trunk.

   After Digiovanni was unsuccessful in opening the trunk,
Trooper Conner resumed his earlier line of questioning con-
cerning drug trafficking activity at about 12:01:41 p.m. He
asked Digiovanni if he was sure there was no marijuana in the
trunk of the car, to which Digiovanni said that he was sure
there was not. In response, Trooper Conner observed that he
had "heard people say that before and then" found drugs, so
he asked Digiovanni if he was sure, and Digiovanni
responded that he was "positive." Continuing this line of drug
questioning, Trooper Conner asked, "[s]o if I bring my drug
detection K-9, my partner and my drug detection K-9 up here,
would there be any reason why the dog would alert to the
vehicle?" Digiovanni replied, "[n]ot at all." Trooper Conner
6                     UNITED STATES v. DIGIOVANNI
asked Digiovanni again if he was sure, and Digiovanni once
again responded that he was "[p]ositive." This second inquiry
concerning drug trafficking activity lasted about one minute.

   Trooper Conner returned to his vehicle at about 12:02:37
p.m. Trooper Conner requested back up assistance, because
he "believed" Digiovanni "was engaged in criminal activity."
He then began the process of checking Digiovanni’s driver’s
license, at 12:03:31 p.m., over ten minutes after Digiovanni
was stopped. At approximately 12:07:22 p.m., Trooper Con-
ner removed his hat, exited his patrol car, and approached
Digiovanni. Although the driver’s license check was not com-
pleted by this time, a dispatcher informed Trooper Conner
that Digiovanni was not wanted on any outstanding warrants.
Trooper Conner told Digiovanni he was "waiting on [the]
license check," adding that "things are looking good," because
he was not wanted on any warrants. At 12:08:15 p.m.,
Trooper Conner told Digiovanni he was "preparing" a warn-
ing ticket for him, adding that there was "no fine" and "no
points." At 12:08:25 p.m., Trooper Conner returned to
Digiovanni his driver’s license and the rental contract, and
issued him a warning ticket and a brochure explaining "what
to expect on a traffic stop."4 At the same time, Trooper Con-
ner said, "[h]ere you go, sir. You are free to go." Immediately
(12:08:27 p.m.), Trooper Conner reminded Digiovanni that
they "were talking, . . . were talking about drugs." He then
observed that "we do have a bad problem out here, people
smuggling drugs on the interstate." After implying that
    4
     It is not entirely clear from the record when Trooper Conner began to
fill out the warning ticket, although it is clear that he completed it after he
called in Digiovanni’s driver’s license to the dispatcher. The warning
ticket issued to Digiovanni contains the date and time of the stop, his driv-
er’s license number, the initials for the State of Massachusetts, Digiovan-
ni’s full name, initials for his race and sex, the car’s license plate number,
the initials for the state in which the plates were issued, the year and make
of the car, the location of the stop, and a few miscellaneous letters and
numbers. A box for "Following Too Closely" is also checked. All total,
there are approximately 100 written characters on the ticket.
                  UNITED STATES v. DIGIOVANNI                    7
Digiovanni was bound by the earlier given verbal consent to
search, Trooper Conner asked, "[m]ay I search your car?," to
which Digiovanni replied, "[y]es." Trooper Conner then
informed Digiovanni that he had a written consent form for
him to sign. Digiovanni then walked toward his car, and
Trooper Conner told Digiovanni to "hold on a second." At
12:09:03 p.m., Digiovanni was provided the written consent
form; he signed it at 12:09:08 p.m.

   During the ensuing search, Trooper Conner and a backup
police officer recovered 34,091 pills of Oxycodone and
$1,450 in United States currency. Digiovanni was arrested
and taken to the Maryland State Police JFK Highway Bar-
racks in Perryville. At the police barracks, after being given
Miranda warnings, Digiovanni made a detailed statement,
explaining, among other things, that he was supposed to be
paid $10,000 for transporting the pills and that he had trans-
ported pills once before.

   On August 5, 2009, a federal grand jury sitting in the Dis-
trict of Maryland returned an indictment charging Digiovanni
with possession with intent to distribute Oxycodone, in viola-
tion of 21 U.S.C. § 841(a)(1). Digiovanni moved to suppress
the physical evidence seized following the search and certain
statements he made to law enforcement officers. The district
court held two hearings, one on March 12, 2010, the other on
March 17, 2010. At the conclusion of the March 17 hearing,
the district court granted Digiovanni’s motion to suppress,
setting forth in open court detailed findings of fact and con-
clusions of law.

   In its analysis, the district court observed that the initial
stop of Digiovanni’s car was "perfectly legitimate." Since the
initial stop was legitimate, the district court noted that the stop
could last no longer than necessary given the stop’s purpose,
absent consent or reasonable suspicion. Because the purpose
of the stop was to issue Digiovanni a warning ticket for trav-
eling too close to a car in front of him, the district court
8                 UNITED STATES v. DIGIOVANNI
observed that, under Fourth Circuit precedent, Trooper Con-
ner was permitted to obtain Digiovanni’s driver’s license and
vehicle registration, run a computer check, and issue the
warning ticket.

   The district court next addressed the length of the stop,
concluding that the stop lasted longer than necessary given
that the purpose of the stop was to issue Digiovanni a warning
ticket for traveling too close to the car in front of him. In so
concluding, the district court found that Trooper Conner did
not proceed with diligence in checking the validity of
Digiovanni’s driver’s license, considering the driver’s license
check was not undertaken until approximately ten minutes
into the stop. According to the district court, rather than
checking the validity of Digiovanni’s driver’s license,
Trooper Conner "diverted . . . from the ordinary purpose of
the traffic stop" and embarked on an unwarranted investiga-
tion into drug trafficking that was not supported by reasonable
suspicion. In rejecting the government’s argument that rea-
sonable suspicion supported the length of Digiovanni’s deten-
tion, the district court noted that the car was rented in Florida
and that Florida is a source state for drugs, as are many other
states on the I-95 corridor. The district court found Digiovan-
ni’s purported initial nervousness of "limited" relevance,
especially since there was "no fumbling in obtaining the
license and rental contract" and Digiovanni was cooperative
throughout the traffic stop. The district court also found
Digiovanni’s "oh boy" comment of limited relevance, because
the comment was not made in response to a question, and
Digiovanni immediately explained why he said "oh
boy"—"[i]t’s just so hot." The district court further found that
Digiovanni’s travel itinerary was "somewhat unusual," given
the expense (including the cost of the Auto Train) and the dis-
tance Digiovanni was driving, though it found that the use of
the Auto Train cut against the government’s argument,
because most drug traffickers would not want to surrender
control of their cars to ride on the Auto Train. The district
court noted that Digiovanni’s appearance and demeanor fit
                  UNITED STATES v. DIGIOVANNI                  9
into the category of a retired person, one traveling from Flor-
ida to the northeast. Moreover, the district court found
Trooper Conner’s reliance on the hanging shirts, the hygiene
bag, and the cleanliness of the car suspect, because he offered
no "reasonable explanation" for relying on these factors.

   Finding no reasonable suspicion to support the length of
Digiovanni’s detention, the district court turned to the issue of
whether Digiovanni’s written consent was voluntary, and, if
so, whether such consent attenuated the taint of the illegal
detention. The district court found that, even though Trooper
Conner used the buzz words, "you are free to go," the encoun-
ter, under the circumstances, was not consensual. According
to the district court, although Trooper Conner used these
words and returned the driver’s license and rental contract, in
virtually the same breath, he immediately returned to the sub-
ject of drugs, implying, falsely, that Digiovanni was bound by
his earlier consent. The district court also noted that the coer-
cive nature of the encounter was compounded by the fact that
Trooper Conner stood in close proximity to Digiovanni. In
view of all of the circumstances before it, the district court
concluded the written consent was involuntary. Alternatively,
the district court seemed to suggest that, even if the written
consent was voluntary, it did not purge the taint of the illegal
detention.

                               II

   The government challenges the district court’s decision,
granting Digiovanni’s motion to suppress. With regard to this
challenge, we review the district court’s factual findings for
clear error and its legal conclusions de novo. United States v.
Perkins, 363 F.3d 317, 320 (4th Cir. 2004).

   The Fourth Amendment guarantees "[t]he right of the peo-
ple to be secure in their persons, houses, papers, and effects,
against unreasonable searches and seizures." U.S. Const.
amend. IV. "[T]he underlying command of the Fourth
10                UNITED STATES v. DIGIOVANNI
Amendment is always that searches and seizures be reason-
able." Wilson v. Arkansas, 514 U.S. 927, 931 (1995).

   When a police officer stops an automobile and detains the
occupants briefly, the stop amounts to a seizure within the
meaning of the Fourth Amendment. Whren v. United States,
517 U.S. 806, 809-10 (1996); see also United States v. Arvizu,
534 U.S. 266, 273 (2002) (noting that the Fourth Amend-
ment’s protection against "unreasonable searches and sei-
zures" extends to "brief investigatory stops of persons or
vehicles"). "As a general matter, the decision to stop an auto-
mobile is reasonable where the police have probable cause to
believe that a traffic violation has occurred." Whren, 517 U.S.
at 810. Any ulterior motive a police officer may have for
making the traffic stop is irrelevant. Id. at 813; see also Ohio
v. Robinette, 519 U.S. 33, 39 (1996) (noting that reasonable-
ness under the Fourth Amendment is evaluated objectively).

   A traffic stop typically begins when a car "is pulled over
for investigation of a traffic violation." Arizona v. Johnson,
129 S. Ct. 781, 788 (2009). It typically ends when the police
officer has "no further need to control the scene, and infor-
m[s] the driver and passengers they are free to leave." Id.

  Because a traffic stop is more analogous to an investigative
detention than a custodial arrest, we treat a traffic stop,
whether based on probable cause or reasonable suspicion,
under the standard set forth in Terry v. Ohio, 392 U.S. 1
(1968). Berkemer v. McCarty, 468 U.S. 420, 439 (1984);
Pennsylvania v. Mimms, 434 U.S. 106, 109 (1977) (per
curiam); United States v. Rusher, 966 F.2d 868, 875 (4th Cir.
1992).

  Pursuant to Terry, we analyze the propriety of a traffic stop
on two fronts. First, we analyze whether the police officer’s
action was justified at its inception. Rusher, 966 F.2d at 875.
Second, we analyze whether the police officer’s subsequent
                  UNITED STATES v. DIGIOVANNI                   11
actions were reasonably related in scope to the circumstances
that justified the stop. Id.

   With regard to Terry’s first prong, there is no dispute that
the traffic stop in this case, at its inception, was justified. See
Md. Code Ann., Transp. art. § 21-310(a) ("The driver of a
motor vehicle may not follow another vehicle more closely
than is reasonable and prudent, having due regard for the
speed of the other vehicle and of the traffic on and the condi-
tion of the highway."); see also United States v. Branch, 537
F.3d 328, 335 (4th Cir. 2008) (noting that a traffic violation
"provides sufficient justification for a police officer to detain
the offending vehicle for as long as it takes to perform the tra-
ditional incidents of a routine traffic stop").

   Under Terry’s second prong, the seizure must be limited
both in scope and duration. Florida v. Royer, 460 U.S. 491,
500 (1983) (plurality opinion). With regard to the scope com-
ponent, "the investigative methods employed should be the
least intrusive means reasonably available to verify or dispel
the officer’s suspicion in a short period of time." Id. With
regard to the duration component, we evaluate "whether the
police diligently pursued a means of investigation that was
likely to confirm or dispel their suspicions quickly, during
which time it was necessary to detain the defendant." United
States v. Sharpe, 470 U.S. 675, 686 (1985); see also Illinois
v. Caballes, 543 U.S. 405, 407 (2005) (noting that a traffic
stop may become "unlawful if it is prolonged beyond the time
reasonably required to complete [its] mission"); Royer, 460
U.S. at 500 (noting that the scope of a seizure "must be care-
fully tailored to its underlying justification," and that the gov-
ernment bears the burden to "demonstrate that the seizure it
seeks to justify . . . was sufficiently limited in scope and dura-
tion to satisfy the conditions of an investigative seizure"). In
the context of traffic stops, police diligence involves request-
ing a driver’s license and vehicle registration, running a com-
puter check, and issuing a ticket. United States v. Foreman,
369 F.3d 776, 781 (4th Cir. 2004); see also Branch, 537 F.3d
12                UNITED STATES v. DIGIOVANNI
at 337 ("If a police officer observes a traffic violation, he is
justified in stopping the vehicle for long enough to issue the
driver a citation and determine that the driver is entitled to
operate his vehicle."). If a police officer seeks to prolong a
traffic stop to allow for investigation into a matter outside the
scope of the initial stop, he must possess reasonable suspicion
or receive the driver’s consent. Branch, 537 F.3d at 336.

   While conducting the tasks associated with a traffic stop, a
police officer’s "questions or actions . . . need not be solely
and exclusively focused on the purpose of that detention."
United States v. Mason, 628 F.3d 123, 131 (4th Cir. 2010).
Rather, a police officer may ask questions unrelated to the
purpose of the stop, "provided that the unrelated questioning
does not extend the encounter beyond the period reasonably
necessary to effectuate the purposes of the lawful detention."
Id.; see also Johnson, 129 S. Ct. at 788 (holding that a law
enforcement officer’s questions "into matters unrelated to the
justification for the traffic stop . . . do not convert the encoun-
ter into something other than a lawful seizure," provided those
questions "do not measurably extend the duration of the
stop"); Muehler v. Mena, 544 U.S. 93, 101-02 (2005) (holding
that unrelated questioning that did not extend a seizure did not
violate the Fourth Amendment); United States v. Soriano-
Jarquin, 492 F.3d 495, 501 (4th Cir. 2007) ("In this case, [the
police officer’s question] did not prolong the stop, as it
occurred while [a] police trainee checked the driver’s license
and registration and prepared his citations.").

   Both Mena and Johnson make clear that unrelated ques-
tioning during an investigative stop, including a traffic stop,
does not run afoul of the scope component of Terry’s prong.
See United States v. Everett, 601 F.3d 484, 494 n.10 (6th Cir.
2010) (noting that Mena and Johnson "stand for the proposi-
tion that mere questioning—on any subject—cannot violate
the scope prong of Terry," and, "[t]herefore, where Terry’s
duration prong is not at issue, as in [those cases], the subject
of the questioning" is irrelevant.). In Mena, police officers
                 UNITED STATES v. DIGIOVANNI                13
entered a house to execute a valid search warrant for weapons
and evidence of gang membership. 544 U.S. at 95-96. During
the search, an INS officer, who had accompanied the police
officers during the execution of the warrant, asked the
detained occupants various immigration-related questions
even though the law enforcement personnel did not possess
reasonable suspicion that anyone in the house was an illegal
immigrant. Id. at 96. The Court upheld the questioning, even
though such questioning was outside of the scope of the justi-
fication for the seizure, because the overall detention was not
extended by the questioning. Id. at 101-02.

   While Mena did not involve a traffic stop, the Supreme
Court’s decision in Johnson did. There, while one police offi-
cer was performing the routine tasks associated with a traffic
stop, another police officer asked a passenger about gang
affiliation. 129 S. Ct. at 784. As in Mena, the unrelated ques-
tioning in Johnson, though outside the scope of the detention,
did not extend the length of time in which the defendant was
detained. Id. at 784-88.

   In Everett, the Sixth Circuit addressed whether unrelated
questioning that lengthens a defendant’s detention gives rise
to a Fourth Amendment violation under the duration compo-
nent of Terry’s second prong. 601 F.3d at 487-96. In that
case, the defendant was stopped for speeding. Id. at 486. After
the defendant exited the car, the police officer "did not imme-
diately continue with what she testified was standard traffic-
stop procedure—i.e., checking for registration and proof of
insurance" (the defendant had earlier informed the police offi-
cer that his driver’s license was suspended), but instead asked
the defendant "‘if he had anything illegal on his person, any
weapons or narcotics or anything like that, or anything illegal
in his vehicle.’" Id. at 487. Early in its analysis, the court
noted that there were two types of prolongation cases, one
where the traffic stop has concluded, in which any subsequent
detention is impermissible without the presence of reasonable
suspicion, and those in which there is some prolongation
14                UNITED STATES v. DIGIOVANNI
before the stop is completed because the police officer is pur-
suing parallel investigative purposes, one related to the justifi-
cation for the traffic stop, the other unrelated. Id. at 492 n.9.
The court further noted that not all prolongation due to unre-
lated questioning violates the Fourth Amendment. Id. at 493.
However, some prolongation becomes "too much" when the
"totality of the circumstances surrounding the stop indicates
that the duration of the stop as a whole—including any pro-
longation due to suspicionless unrelated questioning—was
[un]reasonable." Id. at 494 (internal quotation marks omitted).
According to the court, the reasonableness of a police offi-
cer’s actions during a traffic stop turns on his diligence in
accomplishing the purposes of stop, that is, investigating
whether a traffic infraction occurred and issuing a ticket. Id.
The diligence calculus includes an examination of the subject
matter of the unrelated questioning and whether the unrelated
questioning was conducted out of concern for officer safety.
Id. at 495. A police officer may proceed with diligence, even
though he asks some questions unrelated to the stop, so long
as the police officer’s "overall course of action during a traffic
stop, viewed objectively and in its totality, is reasonably
directed toward the proper ends of the stop." Id. However, dil-
igence is not present where the police officer "definitively
abandoned the prosecution of the traffic stop and embarked
on another sustained course of investigation" or where the
unrelated questions "constituted the bulk of the interaction"
between the police officer and the defendant. Id. (citation and
internal quotation marks omitted). Applying its totality of the
circumstances diligence test to the facts of the case, the court
held the case was not "remotely close," because the single
question could not possibly constitute a definitive abandon-
ment of the investigation of the traffic stop or constitute the
bulk of the encounter between the police officer and the
defendant. Id. at 495-96.

   Recently, in Mason, we addressed the duration component
of Terry’s second prong in the context of a traffic stop. There,
the defendant was pulled over for having excessively tinted
                  UNITED STATES v. DIGIOVANNI                15
windows. 628 F.3d at 126. During the stop, a police officer
asked the defendant and a passenger questions concerning
their travel plans. Id. Such unrelated questioning lasted one to
one and one-half minutes. Id. at 131. Citing Mena and John-
son, we recognized that a traffic stop cannot be extended
beyond the time reasonably necessary to effectuate the pur-
poses of the stop. Id. at 132. Because the police officer "went
about his business promptly and with efficiency" and because
the overall delay caused by the unrelated questioning was de
minimis, we held that there was no Fourth Amendment viola-
tion with regard to the unrelated questioning. Id. In so hold-
ing, we cited case law from this court and our sister circuits
upholding de minimis delays caused by unrelated questioning.
Id. at 132 (citing United States v. Farrior, 535 F.3d 210, 220
(4th Cir. 2008); United States v. Alexander, 448 F.3d 1014,
1017 (8th Cir. 2006); United States v. Purcell, 236 F.3d 1274,
1279 (11th Cir. 2001)).

   To summarize, a traffic stop must be reasonable both in its
scope and duration. Royer, 460 U.S. at 500. Although there is
some debate whether the scope component survives the
Supreme Court’s decisions in Mena and Johnson, see, e.g.,
Reid M. Bolton, Comment, The Legality of Prolonged Traffic
Stops After Herring: Brief Delays as Isolated Negligence, 76
U. Chi. L. Rev. 1781, 1786-87 (2009), the scope of a police
officer’s actions during a traffic stop still is relevant to the
reasonableness analysis under the Fourth Amendment.
Mason, 628 F.3d at 132. This is so because, during a stop, a
police officer must act reasonably, that is, he must diligently
pursue the investigation of the justification for the stop (usu-
ally a traffic infraction), Sharpe, 470 U.S. at 686, to avoid
running afoul of the duration component of Terry’s second
prong. Like other reasonableness determinations, the dili-
gence determination examines the totality of the circum-
stances. Everett, 601 F.3d at 494. Finally, where a delay can
be characterized as de minimis under the totality of the cir-
cumstances, it will not be recognized as a Fourth Amendment
violation. Mason, 628 F.3d at 132; see also Farrior, 535 F.3d
16                UNITED STATES v. DIGIOVANNI
at 219-20 (holding that a minimal delay in conducting a dog-
sniff caused by a police officer’s inexperience was de minimis
where there was no attempt at subterfuge or stalling on the
part of the police officer) (internal quotation marks omitted).

   Turning to our case, we agree with the district court that
Trooper Conner failed to diligently pursue the purposes of the
stop and embarked on a sustained course of investigation into
the presence of drugs in the car that constituted the bulk of the
encounter between Trooper Conner and Digiovanni. In the
beginning, the traffic stop in this case stayed close to the
script approved in cases such as Branch and Foreman.
Branch, 537 F.3d at 337; Foreman, 369 F.3d at 781. Trooper
Conner asked Digiovanni for his driver’s license and the vehi-
cle’s registration. Understandably, he asked Digiovanni to
exit the car. See Mimms, 434 U.S. at 111 n.6 (holding that,
"once a motor vehicle has been lawfully detained for a traffic
violation, the police officers may order the driver to get out
of the vehicle without violating the Fourth Amendment’s pro-
scription of unreasonable searches and seizures"). However,
Trooper Conner’s actions and questions that followed bespeak
an utter lack of diligence. He asked Digiovanni numerous
questions concerning his travel history and travel plans, only
a few of which possibly related to the justification for the
stop. At the conclusion of this questioning, Trooper Conner
embarked on a sustained investigation into the presence of
drugs, instead of either completing the warning ticket or
beginning the driver’s license check. Such investigation began
with numerous questions concerning the presence of drugs in
the car. After Digiovanni could not open the trunk, Trooper
Conner had yet another opportunity to complete the warning
ticket or begin the driver’s license check. Instead, he contin-
ued his questioning of Digiovanni concerning the presence of
drugs in the car. About ten minutes into the stop, Trooper
Conner returned to his patrol car. Instead of beginning the
driver’s license check, he radioed for back-up assistance.
After doing so, Trooper Conner finally relayed Digiovanni’s
driver’s license information to the dispatcher, and, thereafter,
                  UNITED STATES v. DIGIOVANNI                 17
completed the warning ticket. Approximately fifteen minutes
into the stop, Trooper Conner returned to Digiovanni his driv-
er’s license and the rental contract, and issued him a warning
ticket. In the same breath, he returned to the subject of drugs.
Under the totality of the circumstances, we agree with the dis-
trict court that Trooper Conner did not diligently pursue the
traditional purposes of a traffic stop, i.e., investigating
whether a traffic infraction occurred and issuing a ticket. See
United States v. Peralez, 526 F.3d 1115, 1121 (8th Cir. 2008)
(holding defendant’s Fourth Amendment rights were violated
where police officer engaged in a "‘blended process’" of con-
ducting a routine traffic stop and a drug investigation, by ask-
ing questions related both to the traffic stop and the drug
investigation, and the "off-topic questions more than doubled"
the time the defendant was detained and "constituted the bulk
of the interaction between the trooper and the van’s occu-
pants").

   On appeal, the government makes four arguments seeking
to excuse Trooper Conner’s lack of diligence. First, the gov-
ernment argues that any delay caused by the unrelated ques-
tioning was de minimis, and, therefore, Digiovanni’s Fourth
Amendment rights were not violated. According to the gov-
ernment, our case is much like the Mason case, where the
delay caused by the unrelated questioning was one to one and
one-half minutes.

   We reject the government’s reliance on Mason. The delay
in this case was not de minimis. The unrelated questioning
was extensive and time-consuming. It started with some unre-
lated questioning concerning Digiovanni’s travel plans and
morphed into unrelated questioning concerning the presence
of drugs. The record, in particular the video, makes clear that
at just about every turn Trooper Conner was conducting a
drug investigation instead of a traffic infraction investigation.
Indeed, the bulk of the encounter between Trooper Conner
and Digiovanni involved a drug investigation, as the driver’s
18                UNITED STATES v. DIGIOVANNI
license check did not even begin until approximately ten min-
utes into the stop, and, in fact, it never was completed.

   Second, the government argues that, because the overall
length of the traffic stop (approximately fifteen minutes) was
reasonable, there was no Fourth Amendment violation. We
reject this argument.

   We have emphasized that "[t]he maximum acceptable
length of a routine traffic stop cannot be stated with mathe-
matical precision." Branch, 537 F.3d at 336; see also United
States v. Brigham, 382 F.3d 500, 511 (5th Cir. 2004) (noting
that there is "no constitutional stopwatch on traffic stops");
see also Robinette, 519 U.S. at 39 (noting that the determina-
tion of reasonableness does not lend itself to bright-line rules).
This is so because a multitude of factors can affect the length
of a traffic stop, some working in favor of the government,
others in favor of the defendant. For example, some computer
checks will take longer than others, depending on the speed
of the computers involved and whether the car’s occupants
possess in-state or out-of-state identifications. Cf. United
States v. Boyce, 351 F.3d 1102, 1106-07 (11th Cir. 2003)
(noting that a reasonable delay in obtaining the results of a
criminal history check does not run afoul of the Fourth
Amendment). A routine traffic stop also can lengthen in time
where the driver or one of the passengers provides inaccurate
information. Branch, 537 F.3d at 336. At the same time, a
traffic stop can lengthen where a police officer seeks to inves-
tigate a crime completely unrelated to the event that provided
the justification for the stop in the first place. Peralez, 526
F.3d at 1120-21.

   More importantly, the government’s argument fails to rec-
ognize that investigative stops must be limited both in scope
and duration. Creating a rule that allows a police officer fif-
teen minutes to do as he pleases reduces the duration compo-
nent to a bright-line rule and eliminates the scope inquiry
altogether. In its reasonableness jurisprudence, the Supreme
                  UNITED STATES v. DIGIOVANNI                 19
Court has "consistently eschewed bright-line rules," Robi-
nette, 519 U.S. at 39, and the scope of a police officer’s
actions remains relevant in the Fourth Amendment traffic stop
inquiry. Mason, 628 F.3d at 132.

   Third, the government contends that Trooper Conner was
entitled to abandon the traffic infraction purpose of the stop
because he had reasonable suspicion that criminal activity was
afoot. The concept of "reasonable suspicion" "is not readily,
or even usefully, reduced to a neat set of legal rules, but,
rather, entails common sense, nontechnical conceptions that
deal with factual and practical considerations of everyday life
on which reasonable and prudent persons, not legal techni-
cians, act." Foreman, 369 F.3d at 781.

   The Supreme Court has recognized that factors consistent
with innocent travel can, when taken together, give rise to rea-
sonable suspicion. United States v. Sokolow, 490 U.S. 1, 9
(1989) ("Any one of these factors is not by itself proof of any
illegal conduct and is quite consistent with innocent travel.
But we think taken together they amount to reasonable suspi-
cion."). The articulated innocent factors collectively must
serve to eliminate "a substantial portion of innocent travelers
before the requirement of reasonable suspicion will be satis-
fied." Foreman, 369 F.3d at 781.

  The reasonable suspicion standard is an objective one, so
we examine the facts within the knowledge of Trooper Con-
ner to determine the presence or nonexistence of reasonable
suspicion. Id. "Additionally, it must be noted that, because the
Terry reasonable suspicion standard is a commonsensical
proposition, ‘[c]ourts are not remiss in crediting the practical
experience of officers who observe on a daily basis what tran-
spires on the street.’" Id. at 782 (quoting United States v.
Lender, 985 F.2d 151, 154 (4th Cir. 1993)).

   In deciding to prolong the traffic stop to allow for an inves-
tigation into drug trafficking activity, Trooper Conner relied
20                UNITED STATES v. DIGIOVANNI
on the following facts: (1) the car was rented; (2) the car was
coming from a known drug source state (Florida); (3) the car
was traveling on I-95, a known drug corridor; (4) the car was
clean; (5) two shirts were hanging in the rear passenger com-
partment; (6) there was a hygiene bag on the back seat; (7)
Digiovanni’s hands were trembling when he handed over his
driver’s license and the rental contract; (6) during the travel
history questions, instead of answering the question, "[s]o
you’re coming from Florida?," with a "yes," Digiovanni
replied, "I have property in Florida"; (8) Digiovanni’s travel
itinerary; and (9) Digiovanni’s "oh boy" comment.

   In United States v. Foster, 634 F.3d 243 (4th Cir. 2011), we
expressed "concern about the inclination of the Government
toward using whatever facts are present, no matter how inno-
cent, as indicia of suspicious activity." Id. at 248. The same
can be said about many of the facts relied upon by Trooper
Conner. Trooper Conner’s reliance on the hanging shirts bor-
ders on the absurd. He labeled them as suspicious because
non-drug traffickers would pack the shirts in a clothing bag.
While it is true that we rely upon the "experience and special-
ized training" of the police officer, United States v. Johnson,
599 F.3d 339, 343 (4th Cir. 2010), the "Government must also
be able to either articulate why a particular behavior is suspi-
cious or logically demonstrate, given the surrounding circum-
stances, that the behavior is likely to be indicative of some
more sinister activity than may appear at first glance." Foster,
634 F.3d at 248. Here, the government offered no plausible
explanation to support Trooper Conner’s reliance on the two
hanging shirts. Equally absurd is Trooper Conner’s reliance
on the clean car and the hygiene bag on the back seat. The
vast majority of rental cars are delivered to the renter clean,
and, considering that Digiovanni took the Auto Train, it is not
surprising that the car was clean when it was stopped by
Trooper Conner. And there is nothing suspicious about a
hygiene bag located on the back seat of a car.

   There is no question that Trooper Conner was entitled to
rely to some degree on Digiovanni’s trembling hands. See Illi-
                  UNITED STATES v. DIGIOVANNI                 21
nois v. Wardlow, 528 U.S. 119, 124 (2000) ("[N]ervous, eva-
sive behavior is a pertinent factor in determining reasonable
suspicion"). However, the district court understandably dis-
counted this fact, because, as the video reveals, Digiovanni
appeared calm and cooperative throughout the encounter. See
Mason, 628 F.3d at 129 (relying on police officer’s testimony
that an innocent individual’s initial nervousness usually sub-
sides). With regard to the "oh boy" comment, we cannot dis-
turb the district court’s finding that this comment was not an
expression of nervousness (and could not plausibly be con-
strued as such), but rather a comment concerning the hot July
weather. Moreover, our review of the video reveals that
Trooper Conner’s characterization of the "oh boy" comment,
as well as his reliance on Digiovanni’s answer to his "[s]o
you’re coming from Florida?" question, are examples of "post
hoc rationalizations to validate those seizures that happen to
turn up contraband." Foster, 634 F.3d at 249.

   With regard to the car rental, the traveling on I-95, and the
traveling from Florida factors, there is little doubt that these
facts enter the reasonable suspicion calculus. See United
States v. Brugal, 209 F.3d 353, 358 (4th Cir. 2000) (en banc)
(citing car rental travel along I-95 from a source city as fac-
tors contributing to reasonable suspicion). With regard to
Digiovanni’s travel itinerary, Trooper Conner certainly was
entitled to rely, to some degree, on its unusual nature in deter-
mining whether criminal activity was afoot. Id. at 360-61
(noting that an unusual travel itinerary, coupled with other
facts, can support a finding of reasonable suspicion).

   Nevertheless, we agree with the district court that reason-
able suspicion was not present to turn this routine traffic stop
into a drug investigation. The articulated facts, in their total-
ity, simply do not eliminate a substantial portion of innocent
travelers. Id. at 361. When he was stopped, Digiovanni was
traveling from Florida on I-95 in a car he rented the previous
day. For part of the trip, he took the Auto Train. Digiovanni’s
Auto Train trip clearly cuts against the government’s argu-
22                UNITED STATES v. DIGIOVANNI
ment, because drug traffickers routinely avoid places such as
airports and train and bus hubs to evade law enforcement
and/or drug detention dogs. Moreover, because a driver is
separated from his car on the Auto Train, it is unlikely that a
drug trafficker would use this mode of transportation. It is
true that Digiovanni’s travel itinerary is unusual—not many
people are flying from Boston to Miami for the weekend,
renting a car for the return trip to Boston, traveling part of the
way on the Auto Train, and stopping in New York to pick up
some paintings. The problem for the government is that this
unusual travel itinerary is not keyed to other compelling
suspicious behavior. For example, in Brugal, the defendant’s
unusual travel itinerary was coupled with other compelling
suspicious behavior. Id. at 360-61 (holding that unusual travel
itinerary, coupled with, among other factors, evidence of
flight, and defendant’s implausible story that he exited the
interstate to look for gas at an exit that showed no signs of
activity created reasonable suspicion permitting the continua-
tion of a traffic stop). In this case, other than Digiovanni’s
unusual travel itinerary, there is nothing compellingly suspi-
cious about the case. There is no evidence of flight, suspicious
or furtive movements, or suspicious odors, such as the smell
of air fresheners, alcohol, or drugs. All the government can
link to the unusual travel itinerary are the facts that
Digiovanni rented a car from a source state, was stopped on
I-95, and was initially nervous. Such facts, without more, sim-
ply do not eliminate a substantial portion of innocent travel-
ers. Id. at 361.

   Finally, the government argues that Digiovanni’s voluntary
written consent to search the car was an act of free will that
purged the taint of any alleged Fourth Amendment violation
arising from the illegal seizure. Because the purported act of
free will is Digiovanni’s consent to search, the government
must prove by a preponderance of the evidence that his con-
sent to search was voluntary and that his consent was an act
of free will sufficient to purge the taint of the Fourth Amend-
ment violation. Brown v. Illinois, 422 U.S. 590, 603-04
                  UNITED STATES v. DIGIOVANNI                 23
(1975); United States v. Seidman, 156 F.3d 542, 549-50 (4th
Cir. 1998).

   Although the Fourth Amendment generally prohibits war-
rantless searches, the general requirement for a warrant does
not apply where valid consent to the search is given. Schnec-
kloth v. Bustamonte, 412 U.S. 218, 219 (1973); United States
v. Buckner, 473 F.3d 551, 553 (4th Cir. 2007). "Consent to
search is valid if it is (1) knowing and voluntary and (2) given
by one with authority to consent." Buckner, 473 F.3d at 554
(citations and internal quotation marks omitted). The govern-
ment bears the burden of establishing, by a preponderance of
the evidence, that it obtained valid consent to search. Id.

   Whether a defendant’s consent to a search is voluntary is
a factual question, and, therefore, is reviewed under the
clearly erroneous standard. Bustamonte, 412 U.S. at 248-49.
We may reverse the district court’s finding concerning volun-
tariness only if "it can be said that the view of the evidence
taken by the district court is implausible in light of the entire
record." United States v. Lattimore, 87 F.3d 647, 651 (4th Cir.
1996).

   In assessing voluntariness of the consent, we examine the
totality of the circumstances including factors such as the
characteristics of the accused, his education and intelligence,
the number of officers present, along with the location and
duration of the stop. Id. Whether the person giving consent
knew that he possessed a right to refuse consent also is rele-
vant in determining the voluntariness of consent, although the
government need not demonstrate that the person giving con-
sent knew of his right to refuse consent to prove that the con-
sent was voluntary. Id.; United States v. Boone, 245 F.3d 352,
362 (4th Cir. 2001).

   In this case, we cannot say that the district court’s finding
that Digiovanni’s written consent was involuntary is implausi-
ble. On the one hand, Digiovanni was in his late 50s, neither
24                UNITED STATES v. DIGIOVANNI
too young nor too old, and the video demonstrates that he is
reasonably intelligent. The encounter was in public and in
broad daylight, Trooper Conner was the only officer on the
scene, and his weapon was not drawn. See United States v.
Wilson, 895 F.2d 168, 172 (4th Cir. 1990) (holding that the
defendant’s consent, which was given when the defendant
shrugged his shoulders and raised his arms in response to a
police officer’s request to pat the defendant down, was volun-
tary because the police officer was dressed in plain clothes,
made no threats, displayed no weapons, and asked for consent
in public). Trooper Conner also returned Digiovanni’s license
and rental contract. See Farrior, 535 F.3d at 219 ("The fact
that Officer Morris had returned Farrior’s license and registra-
tion also strongly indicates that the encounter was consensual
and that no seizure occurred within the meaning of the Fourth
Amendment."). On the other hand, the district court was free
to conclude that the seizure continued even though Trooper
Conner used the magic buzz words "you are free to go," as
such a statement is not "‘talismanic’" or sufficient in and of
itself to show a lack of custody." United States v. Hargrove,
625 F.3d 170, 180 (4th Cir. 2010).

   Moreover, Trooper Conner’s false implication that
Digiovanni was bound by his earlier consent and his "hold on
a second" statement also suggest that the seizure continued.
While it is true that a consent obtained during an illegal deten-
tion may be voluntary, Boone, 245 F.3d at 362-63, we simply
cannot say that it is implausible to conclude that Digiovanni’s
consent was involuntary, whether he still was seized or not.
The false implication mentioned above and the "hold on a
second" statement set this case apart and lend support to the
plausible conclusion that a reasonable person would not have
felt free to decline Trooper Conner’s request to search the car.
See United States v. Sullivan, 138 F.3d 126, 132 (4th Cir.
1998) (noting that a court must decide, given the totality of
the circumstances, whether "a reasonable person in the sus-
pect’s position ‘would have felt free to decline the officers’
requests or otherwise terminate the encounter’") ((quoting
                     UNITED STATES v. DIGIOVANNI                         25
Florida v. Bostick, 501 U.S. 429, 438 (1991)); cf. United
States v. Molt, 589 F.2d 1247, 1251-52 (3d Cir. 1978) (hold-
ing consent involuntary where agents misrepresented their
statutory authority). This point is supported by the fact that
Digiovanni took just five seconds to review and sign the form
after he had received it, and by the fact that he was subjected
to extensive questioning concerning drugs during an illegal
seizure. The close proximity of Trooper Conner to
Digiovanni, and Trooper Conner’s authoritative demeanor
further support the district court’s finding. In sum, under the
extremely deferential standard of review, we must reject the
government’s challenge to the district court’s finding that
Digiovanni’s consent was involuntary.5

                                    III

  For the reasons stated herein, the judgment of the district
court is affirmed.

                                                            AFFIRMED




  5
   Because we are affirming the district court’s finding that Digiovanni’s
written consent was involuntary, we need not address whether a valid con-
sent purged the taint between the illegal detention and the discovery of the
evidence. See Brown, 422 U.S. at 603-04 (noting that the attenuation test
includes the following factors: the time between illegality and acquisition
of evidence; the presence of intervening circumstances; and the purpose
and flagrancy of official misconduct); Seidman, 156 F.3d at 549-50
(applying attenuation test).
