After the district court denied his motion to suppress, Brandon Odum entered a conditional plea of guilty to the charge that he had possessed with the intent to distribute approximately 5.8 kilograms of a substance containing cocaine in violation of 21 U.S.C. § 841(a)(1). He now appeals that conviction, arguing that the district court erred in refusing to suppress the cocaine found by law enforcement agents in a suitcase Odum had transported from Houston to Chicago. Because the district сourt considered improper facts in determining that the agents had reasonable suspicion to support their detention of the suitcase, we remand to enable the district court to reconsider that question without reference to the improper facts.
*1281 I.
The facts relevant to the suppression issue are derived from Odum’s affidavit, which was incorporated into his motion, from the complaint for search warrant prepared by DEA Narcotics Task Force Agent Martin Gainer, and from the testimony of Agent John Mal-loy, also of the Narcotics Task Force, at Odum’s December 7, 1993 detention hearing.
On November 30,1993, immediately before the departure of a Southwest Airlines flight from Houston to Chicago, Odum paid cash for a pre-reserved one-way ticket. Odum asked the ticket agent for cellophane tape to secure the locks on a yellow, hard-sided suitcase, which he then checked with the airline for the trip to Chicago. Because Odum had рurchased his ticket and checked the suitcase so close to the flight’s departure time, the suitcase was affixed with a late check-in tag. As Odum proceeded to his flight, the Southwest ticket agent reported her encounter with Odum to Officer Griff Maxwell, a Houston police officer assigned to the airport. Maxwell then called Agent Gainer in Chicago, relaying what he had learned from the ticket agent. Maxwell told Gainer that an African-American male of medium height had approached the Southwest ticket counter immediately before the departure of a Chicago flight and purchased a one-way ticket with cash. Maxwell explained that the man had asked the ticket agent for cellophane tape to secure the locks on a yellow, hard-sided suitcase, and that he had then checked the suitcase with the agent. Maxwell told Gainer that the man was carrying a black shoulder bag, that he was traveling under the name Brent Owens, and that his reservation for the flight had been made the previous evening.
Gainer then went with other, agents to Chicago’s Midway Airport to meet the Southwest flight, which was scheduled to arrive at 10:30 a.m. The agents positioned themselves directly across from the arrival gate and observed the passengers deplane. An African-American male with a black shoulder bag eventually emerged from the gate and proceeded down the concourse. Agent Gainer followed the man’and observed him turn his hеad twice to look back over his shoulder, scanning the area behind him. As he made a right turn toward the baggage claim area, the man again looked back over his shoulder. The man entered the baggage claim area and waited for the arrival of the luggage from the Southwest flight. When he saw the yellow suitcase on the baggage carousel, the man approached it, looked around, and then lifted it from the carousel. Agent Gainer saw that the suitcase was large and thаt it had tape over the locks. At this point, the man made direct eye contact with Gainer and maintained it for a moment before looking away. The man then left the baggage claim area after showing his claim check to a security guard.
Agents Gainer and Malloy approached Odum, identified themselves as police officers, and asked to speak with him. Although both agents were dressed in civilian clothes, they displayed identification to confirm that they were policе officers. Odum agreed to speak with the agents because, according to his affidavit, he initially wanted to cooperate by answering their questions. Gainer first inquired whether Odum had come into Chicago on the Southwest flight from Houston, and Odum stated that he had. Gainer then told Odum that he was not being accused of any crime and that he was not under arrest but that if Odum did not mind, Gainer wanted to ask him a few more questions. Odum told Gainer to “go ahead.”
Gainer then asked to see Odum’s airline ticket. Odum showed the agеnt a ticket that had been purchased with cash earlier that day. The ticket bore the name “Brent Owens.” Gainer asked if Odum had any personal identification, and Odum responded that he did not. 1 In response to a series of questions, Gainer then learned that the yellow suitcase belonged to Odum, that Odum had packed part of the suitcase himself, that his sister had packed the other part, that *1282 Odum alone had packed the black shoulder bag, and that no third ppty had given Odum any packages to bring to Chicago.
At this point, Odum asked the reason for Gainer’s questions, and the agent told Odum that he and Malloy were conducting a narcotics investigation at the airport in order to intercept controlled substances coming into and going out of Chicago. Odum began to shake upon hearing Gainer’s response and then wiped his mouth with the back of his hand. According to Odum, he initially had been willing to answer the agents’ questions, but as those questions became more personal, he became hesitant and nervous, and he wished to leave the encounter.
Gainer then asked Odum for permission to search the yellow suitcase. Odum inquired as to what would occur if he refused, and Gainer explained that the suitcase would be detained for a scent search by a trained narcotics detection dog. The agent told Odum that if the search resulted in a positive scent for narcotics, he would apply for a search warrant that would enable him to open the suitcаse. If the scent search was negative, however, the suitcase would be mailed to Odum at any address he designated. Thus aware of the implications, Odum refused to consent to a search of the yellow suitcase. 2 Gainer then asked Odum to accompany the agents to their office at the airport so that a receipt for the suitcase could be prepared and Odum’s identification verified. Odum agreed and carried the suitcase to the agents’ office.
Once in the office, the agents posed additional questions and learned Odum’s address and various telephone numbers. They also learned that their suspect’s real name was Brandon Odum rather than Brent Owens. When asked about the name on his airline ticket, Odum told the agents that he had not purchased that ticket. When asked who did, Odum gave no response.
The agents then verified Odum’s address with his grandmother and prepared a receipt for the yellow suitcase. Before Odum left, the agents asked whether he was carrying a large amount of money. Odum first said “not much,” then admitted to having “about $1,500.” He then produced two bundles of cash that contained $1,600. The agents returned the cash after counting it, and Odum left the office.
A canine search of Odum’s suitcase produced a positive sniff for narcotics. The agents procured a search warrant and discovered approximately 5.8 kilograms of a substance containing cocaine. Odum was arrested and eventually indicted on one count of possessing with the intent to distribute cocaine.
Odum moved to suppress the cocaine as having been procured in violation of the Fourth Amendment. He also requested an evidentiary hearing. The government initially submitted only a brief response to Odum’s motion, but the district court struck that response and ordered the government to submit a more complete response, which it did.
The district court subsequently denied Odum’s motion without an evidentiary hearing. The court determined that Odum had not been “seized” for purposes of the Fourth Amendment when the agents initially stopped him for questioning near Midway’s baggage claim area. The court found that the questioning there was not coercive, that Odum had chosen to cooperate by answering the agents’ questions, and that he understood that he was free to refuse to answer and to leave the encounter. The court therefore found that neither probable cause nor reasonable suspicion was necessаry to support this consensual interview. That conclusion has not been challenged in this appeal.
The court also found, however, that the consensual interview developed into an investigatory stop, and hence a “seizure” under the Fourth Amendment, once the agents declared that they would detain Odum’s suit-ease to have it sniffed by a narcotics detection dog. Yet the court concluded that the agents by this time were aware of sufficient facts to create a reasonable suspicion that *1283 Odum was involved in narcotics trafficking. The court pointed to the agents’ knowledge: (1) that Odum had paid cash for a one-way ticket from Houston, a source city for narcotics, immediately before the flight’s departure; (2) that upon arriving in Chicago, Odum had scanned the concourse as he walked and had looked over his shoulder three times on the way to the baggage claim area; (3) that Odum had been unable to produce any personal identifiсation; (4) that he had become shaky and nervous upon learning the purpose of the agents’ questions; and (5) that Odum had been traveling under a different name, which he justified with the explanation that he had not purchased his own ticket without responding to the question of who had purchased the ticket for him. The court found that although any one of these factors may arguably be consistent with the conduct of an innocent traveler, when taken together, they provided a reasonablе suspicion that Odum was involved in narcotics trafficking. The court therefore denied Odum’s motion to suppress, prompting him to enter a conditional plea of guilt. The district court subsequently sentenced Odum to an imprisonment term of 120 months.
II.
A.
It is by now well-settled that not all encounters between law enforcement agents and private citizens implicate the Fourth Amendment’s ban on unreasonable searches and seizures.
See, e.g., United States v. Rodriguez,
The first category is an arrest, for which the Fourth Amendment requires that police have probable cause to believe a person has committed or is committing a crime. The second category is an investigatory stop, which is limited to a brief, non-intrusive detention. This is also a Fourth Amendment “seizure,” but the officer need only have specific and articulable facts sufficient tо give rise to a reasonable suspicion that a person has committed or is committing a crime. The third category involves no restraint on the citizen’s liberty, and is characterized by an officer seeking the citizen’s voluntary cooperation through non-coercive questioning. This is not a seizure within the meaning of the Fourth Amendment.
United States v. Johnson,
It is clear, however, that a consensual encounter can develop into an investigatory stop through the conduct of the investigating officers.
See Florida v. Royer,
B.
This circuit reviews the denial of a motion to suppress under a clearly erroneous standard.
McCarthur,
In assessing whether an investigatory stop was supported by reasonable suspicion, “we consider the ‘totality of the circumstances’ as they were presented to the officer at the time of the encounter.”
McCarthur,
Odum contends that the district court violated that rule here when it emphasized in denying his motion that Odum had been traveling under a different name (Brent Owens), had offered in explanation only the fact that he had not purchased his own ticket, and had failed to respond to further inquiries relаting to who had purchased the ticket for him. Odum points out that the agents only obtained this information once they took him to their Midway office to prepare a recéipt for the suitcase. The district court found, however, and the government concedes, that a Fourth Amendment seizure had occurred once the agents informed Odum
*1285
near the baggage claim area that they would detain his suitcase for a sniff search.
See, e.g., McCarthur,
The government concedes, in fact, that the district court’s consideration of these facts was improper, and it requests a remand for clarification or reconsideration of the issue by the district court. (Govt.Br. at 12,14-15.) As we observed above, this court currently reviews a district court’s conclusion that there was reasonable suspicion to support an investigatory stop under a clearly erroneous standard. Our
Spears
opinion explains thаt it is the district court’s task to determine whether law enforcement agents had probable cause or reasonable suspicion to support their actions, and that an appellate panel should not substitute its judgment for that of the lower court.
There would of course be no reason to remand if Odum is correct in arguing that the circumstances here were insufficient as a matter of law to establish a reasonable suspicion of criminal activity.
See Reid v. Georgia,
We cannot agree with Odum that the facts known to the agents here were less detailed and therefore less suspicious than the facts found insufficient as a matter of law in
Reid.
The Supreme Court was concerned in that case that three of the four facts relied on by the lowеr court would apply to “a very large category of presumably innocent travelers,” and that only “the fact that the petitioner preceded another person and occasionally looked backward at him as they proceeded through the concourse” related to Reid’s particular conduct.
C.
Odum finally contends that his motion to suppress should not have been denied without an evidentiary hearing. He argues first that a hearing was necessary to enable him to establish that he had been targeted by the agents for an investigative stop even before they arrived at Midway. He also maintains that a hearing was necessary to dеtermine how much time elapsed after the agents seized the yellow suitcase and before they subjected it to a sniff search. Although the district court is free to conduct an evi-dentiary hearing on remand, we cannot say that the court would clearly err in resolving Odum’s motion without such a hearing.
See Rodriguez,
The district court also was not required to conduct an evidentiary hearing to determine the length of time Odum’s suitcase was detained before it was submitted to a sniff search. Although it is clear that the duration of an investigatory stop may abridge constitutional standards even where there is reasonable suspicion to support it
(see United States v. Place,
III.
Because the district court relied on improper facts in concluding that law enforcement agents had sufficient information to produce a reasonable suspicion that Odum had engaged or was engaging in criminal activity, we remand to enable the district court to reconsider that question without reference to the improper facts.
REMANDED.
Notes
. Agent Malloy testified at the detention hearing that he and Gainer had asked at this point whether "Brent Owens” was the subject's real name. Malloy testified that Odum admitted this was not his name and told the agents that his real name was Brandon Owens. (Dec. 7, 1993 Tr. at 9, 14.) Gainer’s complaint for a search warrant did not mention such an exchange, however, and the district court did not rely on Mal-loy’s testimony on this point.
. Malloy testified that Odum did consent to a search of the black shoulder bag and that he in fact searched the shoulder bag once they arrived at the agents’ office. The search did not reveal any narcotics. (Dec. 7, 1993 Tr. at 13, 15.)
.
See McCarthur,
. The government emphasizes one additional fact that apparently raised the agents' suspicions, although the district court never mentioned this fact in its opinion. (See Govt.Br. at 7 n. 5) The government submits that once the agents learned that Odum had no personal identification, Gainer inquired of the reason for Odum’s travel to Houston. Odum apparently indicated that he had been visiting, but he did not reply when asked who he had been visiting. This alleged fact was recited in the government’s response to Odum's suppression motion (R. 28 at 4), but the government cited no evidence that would establish this fact. We have scoured the evidentiary materials before the district court without finding any mention of this exchange.
. The lower court in Reid had relied on the following four facts in determining that there was reasonable suspicion to conduct an investigatory stop:
(1) the petitioner had arrived from Fort Laud-erdale, which the agent testified is a principal place of origin of cocaine sold elsewhere in the country, (2) the petitioner arrived in the early morning, when law enforcement activity is diminished, (3) he and his companion appeared to the agent to be trying to conceal the fact that they were traveling together, and (4) they apparently had no luggage other than their shoulder bags.
