Bud, the problem is that there is no definition in federal or Indiana appellate case law that defines the term "casual stop". You are making up a definition for the term, but that is your definition, not necessarily what the law says. Constitutionally, what matters when a cop engages in contact with a person is whether the contacted person is being stopped or detained. If the officer has reasonable suspicion that a crime has been committed then the officer may stop the person and briefly detain the person to investigate that. If the officer does not have the reasonable suspicion then the officer cannot make the stop or detain the person. However, cops are free like any other person to simply walk up to someone and start a conversation. So long the person would feel free to terminate the conversation and go that is what the federal courts seem to most often refer to as a "causal encounter" to differentiate it from a Terry "stop". The Supreme Court explains it this way:
Second, law enforcement officers do not violate the Fourth Amendment by merely approaching an individual on the street or in another public place, by asking him if he is willing to answer some questions, by putting questions to him if the person is willing to listen, or by offering in evidence in a criminal prosecution his voluntary answers to such questions. See Dunaway v. New York, 442 U.S. 200, 210 n. 12, 99 S.Ct. 2248, 2255 n. 12, 60 L.Ed.2d 824 (1979); Terry v. Ohio, 392 U.S. 1, 31, 32–33, 88 S.Ct. 1868, 1885–1886, 20 L.Ed.2d 889 (1968) (Harlan, J., concurring); id., at 34, 88 S.Ct., at 1886 (WHITE, J., concurring). Nor would the fact that the officer identifies himself as a police officer, without more, convert the encounter into a seizure requiring some level of objective justification. United States v. Mendenhall, 446 U.S. 544, 555, 100 S.Ct. 1870, 1877, 64 L.Ed.2d 497 (1980) (opinion of Stewart, J.). The person approached, however, need not answer any question put to him; indeed, he may decline to listen to the questions at all and may go on his way. Terry v. Ohio, supra, 392 U.S., at 32–33, 88 S.Ct., at 1885–1886 (Harlan, J., concurring); id., at 34, 88 S.Ct., at 1886 (WHITE, J., concurring). He may not be detained even momentarily without reasonable, objective grounds for doing so; and his refusal to listen or answer does not, without more, furnish those grounds. United States v. Mendenhall, supra, 446 U.S., at 556, 100 S.Ct., at 1878 (opinion of Stewart, J.). If there is no detention—no seizure within the meaning of the Fourth Amendment—then no constitutional rights have been infringed.
Florida. v. Royer, 460 U.S. 491, 497–98, 103 S. Ct. 1319, 1324, 75 L. Ed. 2d 229 (1983).
Note that the inquiry here focuses on whether the person is free to go; i.e. whether there is any detention. That turns on how the situation is viewed by the person being contacted, not whether the officer has reasonable suspicion. So the officer could have reasonable suspicion something is going on, but still engage in a casual encounter. The person contacted in that situation would be free to leave at any time. Now, the officer could change that to a Terry stop detention if he has reasonable suspicion at which point the defendant would NOT be free to leave. He is now detained.
An unpublished opinion of the Sixth Circuit has a nice explanation in a concurring opinion, I think:
Not all police encounters with the public are fourth amendment seizures of the Terry type, as it is recognized that the police have the right to address people conversationally with the hope of voluntary exchange without meeting the standards of the fourth amendment. United States v. Garcia, 866 F.2d 147, 150 (6th Cir.1989). As such, the police have the right to ask member of the public for identification, United States v. Collis, 766 F.2d 219, 221 (6th Cir.), cert. denied, 474 U.S. 851 (1985), can question an individual in a non-threatening manner, United States v. Moore, 675 F.2d 802, 808 (6th Cir.1982), cert. denied, 460 U.S. 1068 (1983), and can ask to examine an individual's airplane ticket, Saperstein, 723 F.2d at 1227. However, permissible police encounters may escalate into Terry -type stops. Circumstances which might indicate that a permissible encounter has been elevated into a Terry stop include: “the threatening presence of several officers, the display of a weapon by an officer, some physical touching of the person, or use of language or tone of voice indicating that compliance with the officer's request might be compelled.” Mendenhall, 446 U.S. at 554.
United States v. Byfield, 948 F.2d 1290 (6th Cir. 1991).
So, it can still be a casual encounter if the person is free to go — i.e. nothing suggests he is detained. The cop could have reasonable suspicion in his head, but if he does nothing to indicate that the person is detained it is still a casual encounter and the 4th Amendment is not applicable. It is only at the point of detention that we ask: did the officer have the necessary reasonable suspicion?
Here, the OP was parked at a gas station. So the cop could have come up to him and start a conversation. No violation of the Constitution whether the cop had reasonable suspicion or not. And that would be a casual encounter up to the point the officer said or did something that would make it appear the person was detained. At that point he'd need the reasonable suspicion and we start looking at the rules for Terry stops. Here the officer had the reasonable suspicion from the start, apparently, so he was entitled to detain the OP from the start and there is still no Constitutional violation. Either way, it appears to be a good contact by the cop and the citation isn't subject to attack on 4th Amendment grounds.