United States Court of Appeals
                            FOR THE EIGHTH CIRCUIT
                                   ___________

                                   No. 07-1649
                                   ___________
                                        *
United States of America,               *
                                        *
             Appellant,                 *
                                        * Appeal from the United States
      v.                                * District Court for the District of
                                        * South Dakota.
Ruben Peralez,                          *
                                        *
             Appellee.                  *
                                   ___________

                             Submitted: December 11, 2007
                                Filed: May 14, 2008
                                 ___________

Before BYE, JOHN R. GIBSON, and MELLOY, Circuit Judges.
                             ___________

MELLOY, Circuit Judge.

       Ruben Peralez was charged with one count of possessing a firearm with an
obliterated serial number after a South Dakota State Patrol trooper found such a
firearm in Peralez’s luggage in a van in which Peralez was a passenger. The district
court granted Peralez’s motion to suppress evidence, including the firearm, concluding
the trooper had violated the Fourth Amendment by improperly extending the duration
of the traffic stop to enable a drug dog to sniff the exterior of the van. The
government appeals. We conclude the traffic stop was improperly extended but the
dog sniff was not a result of that improper extension. Thus, we reverse the district
court’s order granting Peralez’s motion to suppress and remand for proceedings
consistent with this opinion.
                                          I.

       On the afternoon of November 16, 2005, Trooper Mark Schlueter of the South
Dakota Highway Patrol was on duty with his police dog, Drake, who is trained in drug
detection. Trooper Schlueter noticed a full-sized yellow van traveling slowly
southbound on Interstate 29 just south of Sioux Falls. The slowly moving van was
pulling a small trailer loaded with two all-terrain vehicles. The trailer did not have a
rear license plate. Trooper Schlueter pulled alongside the van to check the van’s
license plate, but the plate was obscured by a metal bar from the trailer attachment,
and Trooper Schlueter was unable to see the plate number. Trooper Schlueter decided
to stop the van for violating South Dakota’s license plate law, which requires all
vehicles to display license plates conspicuously, regardless of vehicle’s state of
registration. Trooper Schlueter’s dash-mounted camera recorded the ensuing traffic
stop.

       Trooper Schlueter initiated the traffic stop at approximately 2:42 p.m. Trooper
Schlueter approached the van and asked the driver, Ruben Salinas, for his
identification. Salinas provided Trooper Schlueter with his Texas driver’s license.
The trooper then requested that Salinas accompany him back to the patrol car.
Peralez, who was seated in the front passenger seat of the van, remained in the van
while Trooper Schlueter and Salinas went to the patrol car.

      Once in the patrol car, Trooper Schlueter and Salinas discussed the licensing
requirements for vehicles and trailers. Trooper Schlueter advised Salinas that he must
conspicuously display the rear license plate on his van. At approximately 2:45 p.m.,
Trooper Schlueter told Salinas he would issue a warning ticket to Salinas for the van’s
obstructed license plate. As Trooper Schlueter began to complete the warning ticket,
he asked Salinas general questions about his trip, his family, and his van. Salinas told
Trooper Schlueter that he and his passenger were traveling back to Texas after
working for a few months on a farm in Minnesota. Trooper Schlueter shifted away

                                          -2-
from general conversation, asking Salinas if he would be willing to answer some
questions “about the van” and informing him that he did not have to answer the
additional questions. Salinas agreed to answer Trooper Schlueter’s questions. At this
point, there was “absolutely not” anything about Salinas’s actions or comments
causing Trooper Schlueter to be concerned that criminal activity was afoot.

        Trooper Schlueter engaged Salinas in discussion on topics related to drug
trafficking. He asked Salinas if there were drugs or large amounts of cash in the van.
He asked if anyone had used drugs in the van recently. Trooper Schlueter drew
Salinas’s attention to Drake, who was sitting in the rear of the police car, and noted
he is a canine handler. Trooper Schlueter asked if there was any reason Drake would
indicate to the odor of drugs “when” Drake walked around the van. Salinas said there
were no drugs in the car, denied using drugs himself, and said he knew of no reason
Drake would alert on the van. As to large sums of money, Salinas said Peralez had
$2,800 with him, having recently closed his bank account in Minnesota. When
questioned about whether Peralez had a receipt, Salinas said that Peralez usually
crumpled up his receipts and threw them away after receiving cash from the bank.
Salinas did not know the name of Peralez’s bank.

       Trooper Schlueter had completed about half of the warning ticket when he left
Salinas in the patrol car and walked back to the van to speak with Peralez at
approximately 2:53 p.m. The trooper asked Peralez for his identification, which
Peralez provided, and proceeded to ask Peralez about illegal drugs and large amounts
of cash that might be in the van. Peralez denied there were drugs in the van and stated
he had about $2,500 with him. Peralez explained he did not have a receipt, but he
showed the trooper his checkbook. Trooper Schlueter asked if Drake would alert to
the odor of drugs “when” the drug dog walked around the van, and Peralez said there
was no reason the dog would alert. Trooper Schlueter took Peralez’s identification
and returned to the patrol car.



                                         -3-
      After returning to the patrol car, Trooper Schlueter called to check on both
men’s identification. This routine part of any traffic stop did not occur until ten
minutes after the trooper told Salinas he would receive only a warning ticket.
Dispatch responded regarding Salinas’s license after one minute. Before dispatch
responded on Peralez, Trooper Schlueter took Drake out of the patrol car and walked
him around the van.

      At the driver’s side door, Drake indicated he detected the odor of illegal drugs.
The dog sniff took about one minute. As a result of the indication, Trooper Schlueter
searched the van. The search of the van uncovered a digital scale with marijuana
residue, a revolver with its serial number removed, and a box of bullets. Peralez
claimed he owned all of these items.

       A grand jury indicted Peralez on one count of possessing a firearm with an
obliterated serial number, in violation of 18 U.S.C. § 922(k). Peralez pled not guilty
and moved to suppress the evidence found in the van. A United States magistrate
judge conducted a hearing on Peralez’s motion, at which both Trooper Schlueter and
Peralez testified. The government entered a video recording of the stop into evidence.
The magistrate judge issued a report and recommendation suggesting the district court
grant Peralez’s motion. As relevant to this appeal, the magistrate judge concluded the
trooper unreasonably prolonged the traffic stop and “[t]he prolonged detention was
not de minimis in length under the circumstances of this case nor was the dog sniff
within the scope of the purpose for which the traffic stop was made.”1 Thus, the
magistrate judge concluded “[t]he unlawful detention taints the dog sniff, and the
search based upon the dog sniff.” The district court adopted the magistrate judge’s



      1
          The magistrate judge also rejected the government’s assertion that Peralez
consented to the conversation unrelated to the traffic stop, concluding that “Peralez
was not actually free to leave and no reasonable person would have felt free to leave
. . . .” The government does not appeal that conclusion.

                                         -4-
recommendation and granted Peralez’s motion to suppress. This appeal by the
government followed.

                                          II.

       We have jurisdiction over this interlocutory appeal of a district court’s order
granting a motion to suppress evidence. 18 U.S.C. § 3731. We review the district
court’s findings of fact for clear error, and review de novo whether the search violated
the Fourth Amendment. United States v. Morgan, 

, 630 (8th Cir. 2001).
The government argues that the stop was lawful and that any delay was a de minimis
intrusion that did not violate Peralez’s Fourth Amendment rights. Alternatively, the
government asserts that even if the stop was unreasonably prolonged, the delay did not
cause the discovery of the contested evidence and therefore suppression was not
warranted. In light of the government’s arguments, we consider three issues: (1) was
the stop lawful at its inception; (2) was the stop unjustifiably prolonged, making the
stop inconsistent with the Fourth Amendment; and (3) was any constitutional violation
a but-for cause of obtaining the challenged evidence.

                                          A.

       The Fourth Amendment protects against unreasonable searches and seizures.
U.S. Const. amend. IV. A traffic stop constitutes a seizure under the Fourth
Amendment. See Delaware v. Prouse, 

, 653 (1979). An officer who
observes a violation of the law has probable cause to initiate a traffic stop, and such
a stop comports with the Fourth Amendment. Pennsylvania v. Mimms, 

,
109 (1977) (per curiam). Trooper Schlueter observed an obstructed license plate on
the back of the van, a violation of South Dakota law. Trooper Schlueter had probable
cause to stop the van. See United States v. Bloomfield, 

, 915 (8th Cir.
1994) (en banc). Thus, this traffic stop was lawful at its inception.



                                          -5-
                                             B.

        A constitutionally permissible traffic stop can become unlawful, however, “if
it is prolonged beyond the time reasonably required to complete” its purpose. Illinois
v. Caballes, 

, 407 (2005). During a traffic stop, an officer may detain the
occupants of the vehicle “while the officer completes a number of routine but
somewhat time-consuming tasks related to the traffic violation.” United States v.
$404,905.00 in U.S. Currency, 

, 647 (8th Cir. 1999). The tasks include
“asking for the driver’s license, the vehicle’s registration, as well as inquiring about
the occupants’ destination, route, and purpose.” United States v. Sanchez, 

, 975 (8th Cir. 2005) (internal quotation omitted). An officer may ask passengers
these questions. See United States v. Coney, 

, 857 (8th Cir. 2006). If
complications arise during these routine tasks, the vehicle may reasonably be detained
“for a longer duration than when a stop is strictly routine.” United States v. Olivera-
Mendez, 

, 510 (8th Cir. 2007). Whether a traffic stop “is reasonable in
length is a fact intensive question, and there is no per se time limit on all traffic stops.”

recording from Trooper Schlueter’s patrol car provided the district
court, and this court, with a clear picture of the timing and circumstances of the traffic
stop. The stop lasted for sixteen minutes before Trooper Schlueter got Drake out of
the patrol car. Roughly three minutes into the stop, the trooper told Salinas that he
would receive a warning ticket for the obstructed license plate. During the remaining
thirteen minutes, Trooper Schlueter engaged in what he called a “blended process,”
interspersing drug interdiction questions with the routine processing of a traffic stop
arising from an obstructed license plate. Trooper Schlueter admitted at the
suppression hearing that he “ask[ed] questions unrelat[ed] to the stop,” and that those
questions “prolong[ed] the detention.”




                                            -6-
        Nothing unusual occurred during the traffic stop that would have warranted a
longer-than-typical detention. The trooper determined after three minutes that the
driver of the van need only receive a warning ticket for the obstructed license plate.
While routine tasks remained after that determination, “[o]nce an officer has decided
to permit a routine traffic offender to depart with a ticket, a warning, or an all clear,
the Fourth Amendment applies to limit any subsequent detention or search.” United
States v. Alexander, 

, 1016 (8th Cir. 2006). There was nothing unusual
or out of place with the van’s registration or the driver’s documents. Cf. Olivera-

(sorting through conflicting and incomplete information
provided about registration and license plate justified longer stop than usual);

(delay in processing traffic stop caused by driver’s evasive
answers about his identity and use of false identification). When Trooper Schlueter
eventually submitted a license check for Salinas, it took less than a minute for dispatch
to respond. The stop was delayed because of the trooper’s drug interdiction
questioning, not because of anything related to the investigation or processing of the
traffic violation.

       Our cases recognize two instances when an officer may extend or expand the
scope of a traffic stop beyond the original justification for the stop. First, if the
encounter becomes consensual, the stop may be extended. See, e.g., 

(conversation after the conclusion of traffic stop was consensual, and
therefore extension of the stop was not unconstitutional). Second, if the officer
develops reasonable suspicion that other criminal activity is afoot, the officer may
expand the scope of the encounter to address that suspicion. See, e.g., 

(reasonable suspicion developed during the course of the stop, warranting
expansion). We do not face either of those circumstances. The government does not
claim on appeal that the drug interdiction questions posed to Peralez or the van’s
driver occurred during a consensual encounter. Nor does the government contend that
Trooper Schlueter had reasonable suspicion that the van’s occupants were engaged in
illegal activities when the trooper began asking drug interdiction questions. Indeed,

                                          -7-
Trooper Schlueter testified at the suppression hearing that he did not have any reason
to suspect illegal activity when he shifted the focus of his inquiries. The question
presented by the facts of this case is whether Trooper Schlueter’s “blended process”
of conducting a drug interdiction investigation during the course of a run-of-the-mill
traffic stop violated the Fourth Amendment.

       In Olivera-Mendez we acknowledged a split among the circuit courts as to
whether an officer conducting a traffic stop based upon probable cause violates the
Fourth Amendment “by asking a few questions about matters unrelated to the traffic
violation, even if this conversation briefly extends the length of the 

. Three circuits have found such a brief extension does not constitute a
violation, United States v. Alcaraz-Arellano, 

, 1259 (10th Cir. 2006);
United States v. Burton, 

, 518-19 (6th Cir. 2003); United States v.
Childs, 

, 951-54 (7th Cir. 2002) (en banc), while one has reached the
contrary conclusion, United States v. Pruitt, 

, 1220-21 (11th Cir. 1999).

        We need not decide whether a brief extension would comport with the Fourth
Amendment in the context of a probable-cause stop, because the delay caused by
Trooper Schlueter’s questions cannot be categorized as brief. The cases where our
sister circuits found a brief extension consistent with the Fourth Amendment did not
involve as extensive a departure from routine, traffic-related questions as this case.
Cf. 

(off-topic questioning while the officer wrote
out a warning ticket did not “appreciably lengthen” the detention); 

(“a handful of questions” about illegal activity not unreasonable); 

(one question about marijuana did not make seizure unreasonable).
Here, Trooper Schlueter engaged in a “blended process” of conducting a routine
traffic stop and a drug interdiction investigation. The off-topic questions more than
doubled the time Peralez was detained. The video recording of the traffic stop makes
clear the questions unrelated to the traffic violation constituted the bulk of the
interaction between the trooper and the van’s occupants. This was not a brief

                                         -8-
extension. The extent and duration of the trooper’s focus on non-routine questions
prolonged the stop “beyond the time reasonably required” to complete its purpose.

. This violated Peralez’s Fourth Amendment right to be free
from unreasonable seizures.

                                          C.

       Our conclusion that the traffic stop was unlawfully extended does not end our
inquiry, however. We must determine whether the constitutional violation caused
Trooper Schlueter to obtain the challenged evidence. Only if the constitutional
violation was “at least a but-for cause of obtaining the evidence” is suppression of
evidence the appropriate remedy. 

(citing Hudson
v. Michigan, 

(2006), and Segura v. United States, 

, 815
(1984)). If the extended seizure “enable[d] the dog sniff to occur” suppression is
proper. 

. Here, Trooper Schlueter did not prolong the search
to enable a drug detecting dog to arrive on the scene; Drake was available at the outset
of the stop. Trooper Schlueter indicated to both the driver and Peralez that he
intended to run Drake around the exterior of the van, regardless of the responses to the
trooper’s expanded inquiries. He asked whether there was any reason Drake would
indicate “when” he walked around the van, not “if” he walked around the van.
Moreover, nothing in the record indicates that the answers to the questions posed
during the unlawful expansion of the traffic stop caused Trooper Schlueter to utilize
Drake. The dog sniff was not “the consequence of a constitutional violation.”

.

        Drake’s positive indication during the dog sniff, which provided probable cause
to search the van, caused the discovery of the evidence the government seeks to use
in this prosecution. It took less than a minute for Drake to circle the van and indicate
the presence of contraband. This momentary delay, which occurred while Trooper
Schlueter was waiting for the response to his inquiries about Peralez’s driver’s license,

                                          -9-
did not unreasonably extend the traffic stop. See United States v. Martin, 

, 1002 (8th Cir. 2005) (two-minute delay after conclusion of the traffic stop to
conduct a dog sniff not an unreasonable extension); 

(four-minute delay to conduct dog sniff a de minimis intrusion on Fourth Amendment
rights). This delay would have occurred regardless of the Trooper’s off-topic
questions. Because Peralez’s prolonged seizure for questioning about drug trafficking
was not a but-for cause of obtaining the evidence, suppression is not warranted. See

(holding, in the alternative, that evidence discovered
after a dog sniff should not be suppressed because the dog sniff, and not an earlier
arguably unreasonable extension of the traffic stop, caused the discovery of the
contraband).

                                         III.

      We reverse and remand for proceedings consistent with this opinion.
                     ______________________________




                                        -10-