What you folks need to understand is, that once police focus on a suspect, any and all conversations they have with him/her are for one purpose and one purpose only - to get the suspect to say something that will incriminate him/her. They are not "trying to learn the truth." They don't want to hear the truth, unless it fortifies their already made up minds on the subject of the suspect's guilt.
Even with the police required to give Miranda warnings, the vast majority of misguided suspects will spill their guts to the cops, thinking it will help them out of the situation they find themselves in. Cops lie to suspects at every turn in order to get them to talk, i.e., confess.
The defendant has told the field officers who came to arrest him that he wasn't anywhere near the crime scene. He didn't even know the dead guy. (And this happens to be the truth.) Now, here comes the detective in the "interview" room, following the suspect's arrest:
"Look, I understand how these things happen. He comes at you, you defend yourself. If that's they way it went down, you aren't guilty of anything and should have this whole thing cleared up in a couple of days at the outside. On the other hand, it this investigation proceeds they way it looks now, without your input, you could well be finding yourself headed toward the death penalty. So what happened? Was it self defense?"
Now, all of a sudden, the innocent suspect is being confronted with a choice: implicate yourself in such a manner that you will "have the matter all cleared up in a couple of days" or face the possibility of the death penalty. Ever wonder why innocent people confess to crimes they did not commit?
So that's why Miranda is SO important. I have not had a chance to fully digest the OP yet. When I do, I'll be back . . .
It boils down to public awareness George. Your points are well taken, and expressed on both Prime Time TV and not so prime time TV every day. Now that could conceivably open the door for the "I do not have cable or Satellite TV" defense, granted, but it is unrealistic. The technicalities in which cases are dismissed, are sometimes more the offense. Let's not confuse " Presumed Innocent until proven Guilty in a Court of Law" with the real world either. It did not happen unless the Court said it did, is blind reasoning, not impartial. Whether the Defendant walks or not, rightly or wrongly, lets not approach the issue like morons. I've known Cop's and Official's that have shut people up, to protect them from their mouth's too.