Defendant appeals his convictions, after a trial to the court on stipulated facts, for possession of a controlled substance, ORS 475.992, and unlawful possession of a weapon. ORS 166.250. He contends that the trial court erred in denying his motion to suppress evidence found in a warrantless search of his vehicle. We affirm.
On June 19, 1988, Officer Larkin investigated the theft of a Muscular Dystrophy Association contribution jar from a store in Portland. The store clerk told Larkin that the thief was a thin white man in his mid-twenties, approximately 5'7" or 5'8" with brown hair. The thief was accompanied by a white female and was driving a “full sized goldish-brown or yellowish-tan vehicle, early 70’s, possibly an Olds or Buick.” The clerk said the car was in “rough condition” and gave Larkin the license plate number.
One week later, in a different part of town, Larkin saw a car that fit the description given by the store clerk. Defendant, the man driving the car, also matched the clerk’s description and was accompanied by a man and a woman. Larkin followed the car at 20 to 25 miles per hour for two blocks, during which time he called in a request for the suspect vehicle’s license plate number. Before he received the number, however, and without any signal from Larkin, defendant pulled over and got out of his car. Larkin pulled up behind the car, approached defendant and asked if he could see some identification. When defendant replied that he did not have any, Larkin asked him to take a seat in the back of the patrol car until he could ascertain whether the vehicle had been involved in the theft and whether defendant had a valid license. Shortly thereafter, Larkin asked if he could search the car. Defendant responded, “Go for it.” In the car, Larkin found a small amount of tar heroin, a cigarette pack containing cocaine and a semi-automatic pistol.
On appeal, defendant contends that the drugs and gun were seized after an unlawful stop. The state responds that, by the time the encounter became a stop, Larkin had reasonable suspicion to justify it. Accordingly, the ultimate *326questions are when a stop occurred1 and whether Larkin had reasonable suspicion at that time.
A police officer may stop a person only when he reasonably believes that the person has committed a crime. ORS 131.615(1). A stop occurs when an officer temporarily restrains a person’s liberty by physical force or a show of authority. State v. Kennedy, 290 Or 493, 498, 624 P2d 99 (1981). “A person is ‘restrained’ when, in view of all circumstances, a reasonable person would have believed that he was not free to leave.” State v. Horton, 86 Or App 199, 202, 738 P2d 609 (1987).
We conclude that the initial encounter here was not a stop. Defendant pulled over and got out of his car voluntarily. Although Larkin had been following roughly a car length behind, he did not use the overhead lights or siren on his car or engage in any conduct that would have signaled defendant to stop. He simply followed defendant at the legal speed limit for two blocks. The mere act of driving a marked police car behind another car does not constitute a show of official authority sufficient to constitute a stop. State v. Jackson, 91 Or App 425, 428, 755 P2d 732, rev den 306 Or 661 (1988).
Larkin’s request for identification did not elevate the encounter to a stop. “It is the retention of a license or identification card, usually for investigatory purposes, that restrains a person from leaving.” State v. Jackson, supra, 91 Or App at 428. (Emphasis in original.) Larkin’s request for defendant to sit in the patrol car, after defendant admitted that he had no identification, did constitute a stop. At that point, however, Larkin reasonably believed that defendant had failed to carry a license while operating a vehicle on a public highway, a violation of ORS 807.570(1)(a). Because ORS 807.570(4) allows an officer to detain a person who has violated that statute “for such time as is reasonably necessary to investigate and verify the person’s identity,” the stop was lawful. It was at *327that point that defendant consented to the search of his vehicle.2
Affirmed.
The trial court apparently concluded that the stop occurred when defendant pulled over, because the case was tried on that basis. However, we are not bound by the trial court’s legal conclusions. State v. Miller, 43 Or App 421, 424, 602 P2d 1141 (1979).
Defendant also contends that his consent to search the car was involuntary, because it was the fruit of an illegal stop. However, because we conclude that the stop was lawful, that argument lacks merit.