Appeal from Circuit Court of Brown County. No. 01CF02. Honorable David K. Slocum, Judge Presiding.
 The opinion of the court was delivered by: Justice Myerscough
 Following a stipulated bench trial in May 2002, the trial court found defendant, Adam J. Heather, guilty of unlawful possession of cannabis. 720 ILCS 550/4(e) (West 2000). The trial court sentenced defendant to 24 months' imprisonment with 3 days' credit for time served. Defendant appeals the court's denial of his motion to suppress, arguing the deputy exceeded the scope of his authority by questioning the driver of the vehicle about possible criminal activity after the traffic stop was completed. We agree and reverse in part and vacate in part.
 At the hearing on the motion to suppress in December 2001, deputy sheriff Michael Scott Hainline testified to the following. On August 25, 2000, Hainline was assigned to routine traffic patrol in Brown County. As a significant part of his training for traffic duties, he testified, he underwent drug interdiction training. Hainline testified that this training taught him to go "beyond the initial traffic stop" and to ask different questions and to look for different answers or nonresponsiveness, to observe the body language of passengers, to look for movement within the passenger compartment, and how to identify different types of drugs and drug paraphernalia. In addition to teaching him to identify situations in which a further search may be warranted, the classes taught him techniques to effectuate that search in a manner that would reduce the level of constitutional scrutiny.
 At 4 a.m. on August 25, as Hainline was driving eastbound along U.S. Route 24, he noticed in his side mirror that defendant's westbound car that he had just passed did not have a working registration light. Hainline turned his car around, switching from the eastbound lane to the westbound lane, and upon confirming that the car did not have a working registration light, pulled the car over. As he initiated his squad car's overhead lights, "take-down" lights, and spotlights, Hainline observed movement in the vehicle and noted that it appeared that there were three subjects in the vehicle. Hainline admitted the movement was not unusual.
 After stopping the car, Hainline determined Lucas Roberts was the driver. Hainline testified that he approached the vehicle on the passenger side and that defendant, the passenger in the front seat, initially looked surprised that he had come up on his side instead of on the driver's side. Hainline then introduced himself, stated the reason for the stop, and asked Roberts, the driver of the car, for his license and proof of insurance. Hainline also asked for identification from the defendant and Walter Bartz, the passenger in the rear. Hainline testified that defendant did not directly look at him, except to answer questions about his identity and birth date. Hainline characterized this behavior as suspicious under the "no look test," saying that most passengers will look at the officer just as a show of respect and that it is suspicious if a passenger tries to ignore the officer or pretend that he is not there. Conversely, Hainline testified that Bartz, the passenger in the rear seat, was overly friendly, which also was suspicious behavior. As he was talking to the vehicle's occupants, Hainline smelled a strong odor, although he could not identify the scent, but it could have been food. Hainline testified that a strong odor, even if the smell could not be identified, was often indicative of the masking of drugs or drug use in the car.
 Hainline took the information he received and returned to his patrol car to check that Roberts' driver's license was valid and to run a warrant check on defendant and Bartz. Hainline found that both defendant and Bartz had criminal histories, but Roberts had none. Additionally, Hainline testified that he recalled previously receiving information from the West Central Illinois Drug Task Force that defendant was involved in illegal drug activity. However, Roberts had a valid driver's license and proof of insurance, and no warrants were outstanding for defendant and Bartz, so Hainline exited his patrol car and approached the vehicle, this time from the driver's side. Hainline then asked Roberts to exit his car and to join him at the rear of the car. Roberts complied, and Hainline talked briefly with him while he wrote out a warning ticket. Hainline asked Roberts where they were coming from and what they were doing. Roberts answered that they had been at a friend's house in Beardstown. When asked the name of the person they had visited, Roberts did not answer. Hainline then issued the warning ticket to Roberts and returned his insurance card and driver's license, informing him that he was free to go.
 There is some dispute as to whether Roberts reentered the vehicle and was about to leave or whether he was simply returning to the vehicle. Roberts testified that after Hainline told him he was free to leave, Roberts got back into his vehicle and was preparing to leave when Hainline approached his car window and started questioning him again. According to Hainline, after Roberts received his warning ticket, driver's license, and insurance card, Roberts turned to walk back toward his vehicle. As Roberts was walking away, Hainline asked him if they had any open alcohol in the vehicle. Roberts replied in the negative. Hainline asked him if there were any loaded guns in the car. Roberts answered no. Hainline asked if there were any illegal drugs in the car. Roberts testified he said no. However, Hainline testified that Roberts did not provide an answer, but instead looked down and away from him. Hainline then asked for permission to search the vehicle. Hainline denied telling Roberts that he could keep them there until they consented to a search or until a canine unit arrived. However, Hainline admitted that he may have said other units, including perhaps a canine unit, were in the area and could be on their way. Hainline testified that he did this, not as an intimidation, but out of concern for his own safety, as he was outnumbered three to one. Hainline further testified that the reason he waited to question Roberts about the contents of his vehicle until after he had returned his license and told him he was free to go was to prevent Roberts from saying at trial that he did not feel he was free to leave at that moment.
 After Hainline received consent to search the car, he ordered the passengers out and frisked each of them, finding no weapons or contraband. He then opened the passenger-side door and began a vehicle search, which resulted in his finding a "one-hitter" pipe and a large bag of plant material, which later field tested positive for cannabis.
 Roberts testified that he did not initially consent, but after Hainline told Roberts that he could keep them there until they consented or he brought in a canine to search, Roberts eventually consented.
 Defendant testified that Hainline returned Roberts' driver's license and insurance card and told Roberts he was free to leave. Defendant stated, however, that when Hainline asked permission to search the vehicle, Roberts said no. Defendant further stated that Hainline told Roberts Hainline could detain the car until a canine unit arrived. On cross-examination, defendant admitted that he was not standing near Roberts while Hainline questioned him; rather, defendant remained in the car during the questioning.
 The trial court denied defendant's motion to suppress, finding that (1) the initial traffic stop was permissible, (2) a reasonable person in Roberts' position would believe he was free to leave, (3) the detention was not improperly prolonged, and (4) Hainline had reasonable suspicion to ask for consent to search.
 Following a stipulated bench trial, defendant was found guilty of unlawful possession of cannabis. Defendant filed a posttrial motion, arguing the trial court erred in denying his motion to suppress. On July 29, 2002, the court denied defendant's posttrial motion and sentenced defendant to 24 months' imprisonment. This appeal followed.
 A. Standard of Review
 "When a trial court's ruling on a motion to suppress involves factual determinations or credibility assessments, the court's ruling will not be disturbed on review unless it is manifestly erroneous." People v. Gonzalez, 204 Ill. 2d 220, 223, 789 N.E.2d 260, 263 (2003). However, where the facts and witness credibility are not in dispute, the ultimate question posed by the legal challenge to the court's ruling is reviewed de novo. Gonzalez, 204 Ill. 2d at 223, 789 N.E.2d at 263. In the present case, the court found a reasonable person in defendant's position would have believed he was free to leave, and defendant does not challenge the ...