Opinion for the Court filed by Circuit Judge D.H. GINSBURG.
Dissenting opinion filed by Circuit Judge WALD.
D.H. GINSBURG, Circuit Judge:David Michael Carter was indicted on one count of possession with intent to distribute 50 or more grams of a mixture and *1096substance containing cocaine base, in violation of 21 U.S.C. §§ 841(a)(1) and 841(b)(l)(A)(iii). Following an evidentiary hearing the district court denied Carter’s motion to suppress evidence. Carter, who was later convicted and sentenced to ten years’ imprisonment, appeals the denial of his motion to suppress evidence. We affirm the ruling of the district court.
I. Background
Two plain-clothes detectives from the Narcotics Interdiction Unit of the Metropolitan Police Department boarded an Amtrak train during its brief stopover at Union Station. Detective William Buss noticed one passenger, viz. the appellant, “squirming” in his seat, turning to look out the train window and turning back to look down the aisle as the officers approached. Detective Buss approached Carter, showed his police identification folder, and asked him about his trip. Carter replied that he was travelling from New York City to Fre-dricksburg, Virginia to look for construction work. Detective Buss then asked to see his ticket, which Carter handed to him. The ticket was for a passenger named “C. Carter.” Detective Buss asked to see Carter’s driver’s license, which gave his name as “Michael Carter.” Carter was acting nervously throughout this transaction; indeed, when Detective Buss handed the license back to him, Carter’s hands were trembling so much that he dropped it.
Detective Buss then asked Carter if he was carrying any drugs and Carter said “No.” Detective Buss asked Carter for permission to look in his tote bag and Carter said “Okay.” When Detective Buss searched the bag he found an assortment of new construction tools. In response to a question, however, Carter stated that he had been working in construction all his life, Detective Buss, who has done a lot of construction work himself, thought that the tools were probably a mere prop because Carter was not carrying goggles or a hard hat and because he was carrying a level that would not be used in construction work. Detective Buss also believed that Carter “didn’t have enough clothing to substantiate a trip of undetermined duration.”
As the detective rifled through the tote bag, Carter indicated that he himself would go through the bag and pull out items to show the detective. He tried at least twice to put his hands into the bag, causing Detective Buss to ask, “Do you mind if I do the searching?” Detective Buss then removed from Carter’s tote bag a brown paper bag, which Carter snatched back from him saying, “There’s food in there; I will show you.” At that point, Carter put his hand inside the paper bag, felt around, and finally withdrew his hand — which was empty. He then rolled up the paper bag and stood looking at Detective Buss. The detective stated, “I take it you don’t want me to search that?” and Carter replied, “That’s right.”
Detective Buss told Carter that he was going to take the paper bag to a dog trained to detect narcotics by smell. Although Carter himself was not detained, he followed Detective Buss off the train and onto the platform. Detective Buss took the bag to a different section of the terminal.
While Detective Buss was gone, another officer approached and asked Carter if he had been carrying drugs in the paper bag. Carter admitted that he had been carrying drugs but added that they were not his. The officer then placed Carter under arrest. Moments later, Detective Buss returned and informed the other officers on the platform that the dog’s reaction to the bag was positive and that he had opened the bag and found seventy-nine ziplock bags of apparent crack cocaine.
At his trial, Carter moved under the fourth amendment to the Constitution to suppress the drug evidence and his admission. The district court denied the motion, holding that Carter had consented to the search of his tote bag and that Detective Buss had a reasonable suspicion upon which to detain the paper bag for the purpose of a canine sniff test.
II. Analysis
Carter presents two challenges to the district court’s denial of his motion to *1097suppress. First, he argues that the district court erred in finding that he voluntarily consented to the search of his tote bag. “Because of the fact-bound nature of the inquiry [into voluntariness], we generally reverse a trial judge’s finding only for clear error.” United States v. Lewis, 921 F.2d 1294, 1301 (D.C.Cir.1990). Here Detective Buss testified that Carter said “Okay” when asked if he could search the tote bag. When, because Carter kept putting his hand into the bag, Detective Buss asked, “Do you mind if I do the searching?” Carter removed his hand and again said “Okay.” On these facts, the district court did not err, much less clearly err, in finding that Carter had consented to the search. See United States v. Joseph, 892 F.2d 118, 122 (D.C.Cir.1989) (no reversible error in finding that by reaching into bag during search defendant neither rendered search involuntary nor withdrew consent thereto).
Second, Carter maintains that Detective Buss’s seizure of the paper bag for further investigation was not supported by a reasonable suspicion. See United States v. Place, 462 U.S. 696, 702, 103 S.Ct. 2637, 2642, 77 L.Ed.2d 110 (1983) (police must have reasonable suspicion in order temporarily to detain personal effects for purpose of conducting limited investigation, including sniff by dog). The question whether a police officer acted upon a reasonable suspicion requires that we consider “the totality of the circumstances—the whole picture,” as he saw it. United States v. Cortez, 449 U.S. 411, 417, 101 S.Ct. 690, 695, 66 L.Ed.2d 621 (1981).
Viewing the totality of the circumstances here, we conclude that Detective Buss had a reasonable suspicion based upon (1) Carter’s arrival from a “source” city (New York); (2) his claim to be looking for construction work though he lacked the proper clothing and equipment; (3) his nervous behavior; and (4) his offer to show the food in the paper bag, followed by his removing his empty hand from the bag.
Carter asserts that the district court impermissibly considered his withdrawal of consent in finding reasonable suspicion. We agree. The constitutional right to withdraw one’s consent to a search, see, e.g., Mason v. Pulliam, 557 F.2d 426, 428-29 (5th Cir.1977), would be of little value if the very fact of choosing to exercise that right could serve as any part of the basis for finding the reasonable suspicion that makes consent unnecessary. Cf. Brown v. Texas, 443 U.S. 47, 99 S.Ct. 2637, 61 L.Ed.2d 357 (1979) (defendant’s presence in drug-ridden area and refusal to identify himself to police does not give rise to reasonable suspicion of criminal activity); United States v. Wilson, 953 F.2d 116, 125-26 (4th Cir.1991) (refusal to allow search of coat, after consenting to search of luggage and person, should not have counted as a factor in “reasonable suspicion” analysis). But this insight is immaterial here. For (as the district court also observed) after Carter snatched the bag back from Detective Buss and thus withdrew his consent, he volunteered to show the detective the food he had claimed was in the paper bag. Carter then felt inside the bag, pulled his hand out with nothing in it, rolled up the paper bag, and stood there silently looking at Detective Buss. The detective could reasonably take this conduct into account, as part of the totality of the circumstances, regardless whether it occurred before or, as here, after Carter had given and then withdrawn his consent to a search. See United States v. Jones, 973 F.2d 928, 931 (D.C.Cir.1992) (“A suspect is ‘free to leave’ a non-seizure interview, but when he does so by abruptly bolting after having consented, the officers are free to draw the natural conclusions”). And when added to the other factors enumerated above, Carter’s offer to show the detective the contents of his bag and his peculiar way of retracting that offer gave rise to a reasonable suspicion that he was concealing drugs in his bag, i.e., quite apart from his earlier withdrawal of consent to a police officer’s search.*
*1098III. Conclusion
For the foregoing reasons, the temporary detention of the paper bag for a canine sniff did not violate Carter’s rights under the fourth amendment. The judgment of the district court is therefore
Affirmed.
Contrary to our dissenting colleague’s characterization, we are not ”allow[ing] the police to base the necessary 'reasonable suspicion’ for a luggage detention on the manner in which a person *1098withdraws consent.” Dissent Op. at 1098 (emphasis in original). Carter had withdrawn his consent when he retook the bag. His subsequent offer to show Detective Buss the food did not constitute a second consent, for he did not propose to allow the police officer to search the bag but instead indicated that he would himself show the officer the food he said it contained. For us to countenance the officer’s reasonable suspicion based upon such post-withdrawal conduct in no way bears upon the extent to which a reasonable suspicion may be based upon "the manner" in which consent is withdrawn. Cf. United States v. Wilson, 953 F.2d 116, 126 (4th Cir.1991) ("We are not prepared ... to rule that the form of denial can never be included as a factor to be considered in determining whether an investigative stop was justified") (emphasis in original).