The determination of whether an individual is "in custody" for purposes of Article 38.22 must be made on an ad hoc basis after considering all of the objective circumstances. Police station questioning does not, in and of itself, constitute custody. Dowthitt v. State, 931 S.W.2d 244, 255 (Tex. Crim. App. 1996). There are four general situations that may constitute custody: (1) when the suspect is physically deprived of his freedom in any significant way; (2) when a law enforcement officer tells a suspect he cannot leave; (3) when law enforcement officers create a situation that would lead a reasonable person to believe that his freedom of movement has been significantly restricted; (4) when there is probable cause for arrest and law enforcement officers do not tell the suspect that he is free to leave. Id. at 255. In situations one through three above, the restriction on freedom of movement must amount to the degree associated with an arrest, as opposed to an investigative detention. Id. at 255. The ultimate inquiry is whether there was a formal arrest or restraint on freedom associated with a formal arrest. Stansbury v. California, 511 U.S. 318, 322, 114 S. Ct. 1526, 128 L. Ed. 2d 293 (1994). In situation four, the officers' knowledge of probable cause to arrest must be manifested to the suspect, i.e., custody is established if the manifestation of probable cause, combined with other circumstances, would lead a reasonable person to believe that he is under restraint to the degree associated with an arrest. Dowthitt, 931 S.W.2d at 255. The only relevant inquiry is how a reasonable person in the suspect's shoes would have understood the situation. Stansbury, 511 U.S. at 325.