Article 38.22, section 5 of the code of criminal procedure allows admission of a statement that does not stem from custodial interrogation. See TEX. CODE CRIM. PROC. ANN. art. 38.22, 5 (Vernon 1979). A statement that is not the result of custodial interrogation is admissible against the accused on the question of guilt. See id. art. 38.23(a) (Vernon Supp. Pamph. 2000). The United States Supreme Court has held that a traffic stop, by itself, does not constitute "custody" for Miranda purposes. See Berkemer v. McCarty, 468 U.S. 420, 441, 82 L. Ed. 2d 317, 104 S. Ct. 3138 (1984). While a traffic stop may ripen into a custodial interrogation situation, see Dowthitt v. State, 931 S.W.2d 244, 254-55 (Tex. Crim. App. 1996), the mere fact that a suspect becomes the focus of a criminal investigation does not convert a roadside stop into an arrest. See State v. Stevenson, 958 S.W.2d 824, 829 (Tex. Crim. App. 1997). In Berkemer, the police stop began as a DWI investigation. the driver was asked to take a field sobriety test, which he failed. The officers then asked him whether he had been using intoxicants, to which he replied that he had. The Supreme Court held the driver was not in custody for Miranda purposes until the formal arrest, which did not occur until after his statement. Berkemer, 468 U.S. at 441-42.