Jeffery McNair was convicted in a bench trial for possessing cocaine in violation of Code § 18.2-250. On appeal, he contends that the trial court erred (1) in refusing to suppress evidence seized by the police during a warrantless search of his residence after he reported a robbery, and (2) in refusing to strike the evidence on the ground that it was insufficient to prove the offense. Finding no error, we affirm the conviction.
*562I.
Officer William Hannum responded to a report that a robbery was in progress at McNair’s apartment. McNair, who was “very upset,” told Officer Hannum that he had just been robbed and that he believed the robbers were still inside his apartment. Officer Hannum remained with McNair until two other police officers arrived. Officer Hannum and several other officers then searched McNair’s apartment, “mainly looking for anyone who might have done the robbery ... or any other individuals that might need ... assistance.” During their search of the two-level apartment, which “was in somewhat of a state of disarray, of clutter,” the officers entered McNair’s second floor bedroom. Finding no one in the apartment, the officers returned to the first floor living room and discussed the robbery with McNair.
Detective Willie Wells arrived while Hannum and two other officers were talking to McNair in the living room area. At that time, an emergency crew was removing a victim. The detective asked Hannum whether he or the other officers had looked for clues. Without speaking to McNair about the robbery, the detective then went upstairs “specifically looking for evidence that the robbers might have dropped or left behind.” In McNair’s bedroom, which was in disarray, the detective noticed a glass test tube lying in plain view on the floor in the doorway to a closet. The test tube was intact, contained a white substance, and was wet on the inside. The detective testified that he recognized the tube as a type that “is commonly used to cook up small amounts of crack cocaine.” When the detective questioned McNair about the test tube, McNair said that the robbers must have dropped it when they were in his bedroom. The white substance in the test tube proved to be cocaine.
The trial court convicted McNair of possession of the cocaine.
II.
McNair contends that the test tube was discovered by the police during an unlawful search and that the trial court erred *563in refusing to suppress the test tube and cocaine as evidence. Conceding that exigent circumstances existed when the officers initially arrived at his apartment, McNair argues that the exigency ceased to exist when the officers determined that the robbers were no longer present and no one needed emergency assistance and that the detective’s subsequent warrantless search of the apartment violated the Fourth Amendment. Without conceding that the exigent circumstances had ended when the detective searched the bedroom, the Commonwealth argues that McNair consented to the search. Because we find that the detective’s search was made with McNair’s consent, we affirm the trial court’s refusal to suppress the test tube and cocaine as evidence. We do not address the question of continuing exigency.
When we review a trial court’s denial of a motion to suppress, “[w]e view the evidence in a light most favorable to ... the prevailing party below, and we grant all reasonable inferences fairly deducible from that evidence.” Commonwealth v. Grimstead, 12 Va.App. 1066, 1067, 407 S.E.2d 47, 48 (1991). In our analysis, “we are bound by the trial court’s findings of historical fact unless ‘plainly wrong' or without evidence to support them.” McGee v. Commonwealth, 25 Va.App. 193, 198, 487 S.E.2d 259, 261 (1997) (en banc) (citing Ornelas v. United States, 517 U.S. 690, 699, 116 S.Ct. 1657, 134 L.Ed.2d 911 (1996)).
“[T]he fourth amendment proscribes all unreasonable searches and seizures and ‘ “searches conducted outside the judicial process, without prior approval of a judge or magistrate, are per se unreasonable under the Fourth Amendment — subject only to a few specifically established and well-delineated exceptions.” ’ ” Cantrell v. Commonwealth, 7 Va. App. 269, 282, 373 S.E.2d 328, 334 (1988) (citations omitted). However, searches made by the police with the consent of a person authorized to give consent “do not implicate the fourth amendment.” Iglesias v. Commonwealth, 7 Va.App. 93, 99, 372 S.E.2d 170, 173 (1988); see also Payne v. Commonwealth, 14 Va.App. 86, 88, 414 S.E.2d 869, 869-70 (1992). The Com*564monwealth must prove that, given the totality of the circumstances, the consent was freely and voluntarily given. See Hairston v. Commonwealth, 216 Va. 387, 388, 219 S.E.2d 668, 669 (1975); Commonwealth v. Rice, 28 Va.App. 374, 378, 504 S.E.2d 877, 879 (1998). Once consent is given, the search remains lawful (1) as long as the consenting individual cooperates with the police, and (2) if the police do not exceed the scope of the consent. See Grinton v. Commonwealth, 14 Va.App. 846, 850-51, 419 S.E.2d 860, 862 (1992). While conducting a consensual search, the police may lawfully seize an item that they discover in plain view if they “have probable cause to believe that the item in question is evidence of a crime or contraband.” Conway v. Commonwealth, 12 Va.App. 711, 721, 407 S.E.2d 310, 316 (1991) (en banc).
The officers responded to a report that a robbery was in progress at McNair’s residence. McNair met the responding officers and informed them that the robbers could still be in his apartment. When an initial search of the residence disclosed no suspects, McNair voluntarily assisted the officers by answering questions while standing in the living room of his apartment. At no point did he attempt to restrict or terminate the officers’ investigation.
When Detective Wells arrived, he asked Officer Hannum whether the officers had searched for clues to the robbery. The detective then went upstairs. McNair did not object.
From this evidence, the trial court reasonably inferred that McNair (1) consented to the officers’ presence in his apartment for the purpose of investigating the robbery, (2) observed the detective go upstairs, and (3) knew that the detective was searching for clues. His failure to withdraw his consent is evidence that he consented to the detective’s search. See Lawrence v. Commonwealth, 17 Va.App. 140, 146, 435 S.E.2d 591, 594-95 (1993), aff'd, 247 Va. 339, 443 S.E.2d 160 (1994); see also Grinton, 14 Va.App. at 851, 419 S.E.2d at 863 (“[t]he scope of a search may be further defined during the course of the search by the passive acquiescence of the person whose property is being searched”).
*565McNair argues that the Supreme Court’s ruling in Thompson v. Louisiana, 469 U.S. 17, 105 S.Ct. 409, 83 L.Ed.2d 246 (1984), is controlling. We disagree. Thompson does not address the situation at bar, because the police had McNair’s consent to search for evidence of criminal activity. Indeed, the Court in Thompson specifically explained that it “express[ed] no opinion as to whether the search at issue ... might [have] be[en] justified as consensual.” Id. at 23, 105 S.Ct. 409. Therefore, Thompson does not control our decision.
Once valid consent is given, the police may conduct a reasonable search of a residence until the consent is unequivocally withdrawn. Any items discovered in plain view may be seized by the searching officers and may be used as evidence at trial. The trial court, therefore, correctly denied McNair’s motion to suppress.
III.
McNair next contends that the evidence was insufficient to prove that he possessed the cocaine. He argues that the evidence contained no direct proof of possession by him añd that the circumstantial evidence did not exclude the reasonable hypothesis that the robbers left the test tube in his closet. We disagree.
“To establish possession of a controlled substance, it generally is necessary to show that the defendant was aware of the presence and character of the particular substance and was intentionally and consciously in possession of it.” Gillis v. Commonwealth, 215 Va. 298, 301, 208 S.E.2d 768, 771 (1974). However, constructive possession may be proved through evidence demonstrating “that the accused was aware of both the presence and character of the substance and that it was subject to his or her dominion and control.” Wymer v. Commonwealth, 12 Va.App. 294, 300, 403 S.E.2d 702, 706 (1991). Circumstantial evidence is sufficient to prove guilt beyond a reasonable doubt so long as “all necessary circumstances proved ... [are] consistent with guilt and inconsistent *566with innocence and ... exclude every reasonable hypothesis of innocence.” Bishop v. Commonwealth, 227 Va. 164, 169, 313 S.E.2d 390, 393 (1984). The Commonwealth “need not affirmatively disprove all theories which might negate the conclusion that the defendant ... [possessed the cocaine], but the conviction will be sustained if the evidence excludes every reasonable hypothesis of innocence.” Higginbotham v. Commonwealth, 216 Va. 349, 353, 218 S.E.2d 534, 537 (1975).
When an appellant challenges the sufficiency of the evidence, we view the evidence “in the light most favorable to the Commonwealth and give it all reasonable inferences fairly deducible therefrom.” Id. at 352, 218 S.E.2d at 537. The test tube containing the cocaine was found at the door to McNair’s closet. The detective found moisture on the inside of the test tube, a circumstance consistent with cooking crack cocaine. The detective, who had participated in executing more than one hundred search warrants, testified that in his experience, he had “never located [a test tube] on a person on the street before.” Rather, such items were normally “found in homes during search warrants.” This testimony supports the trial court’s finding that McNair’s suggestion that the robbers had left the test tube was unreasonable. Because the evidence supported no other plausible explanation as to how the test tube came to be in McNair’s closet, the trial court reasonably inferred that the test tube and cocaine belonged to McNair.
Because the trial court did not err in denying McNair’s motion to suppress and his motion to strike, we affirm the judgment of the trial court.
Affirmed.