“Legal contact” refers to any contact that does not violate statutory or constittuional provisions. So, yes, “legal contact” would include a consensual encounter, an investigative detention, and an arrest.
BUT – it would not include a consensual encounter that transformed into a detention without supporting reasonable, articulable suspicion.
So, for example, I’ve been saying repeatedly that as long as a citizen is free to disregard the police inquiry and go about his business, the Fourth Amendment is not implicated. The moment that he’s not free to do that, he’s “seized” within the meaning of the Fourth Amendment, and that seizure must be based on reasonable suspicion. If it isn’t, then the encounter ceases to be a “legal contact.”
So back to the examples:
COP: Hello, gentlemen! How are things?
SUSPECT 1: Todo bien aqui.
SUSPECT 2: (silent)
COP: Say, you guys are both citizens or legal residents, right?
SUSPECT 1: Si, soy norteamericano.
SUSPECT 2: (turns and starts to leave)
COP: Hey, bud – I’m talking to you! Hang on there!
At that point, the encounter ceases to be consensual.