Thank you SO much for going into this with thoroughness. My takeaway is that even without a Miranda warning, if Barry talked to LE, it's admissible (but could be challenged on appeal).
Does it make a difference if what Barry said was not a confession? I mean, what if he just stated a bunch of things that can be shown to be untrue? ("never had a cooler," then cooler is plainly seen on some CCTV or something).
If Barry did outright incriminate himself in some way, during his interrogation, might the Court disallow that?