Since the Miranda warning has been mentioned.
Cops don't have to issue the warning until you are in custody. Basically, until they tell you you're under[arr]est or prevent you from leaving anything you say is fair game.
Unless the rules have changed (yet again) recently, that's not quite true.
The have to issue the Miranda warning before they interrogate your or ask you questions
. Typically the warning is given at the time of arrest or shortly thereafter. However, if the cops don't ask you questions, they don't need to recite the Miranda warning. You can be cuffed, transported and booked into jail before you hear the warning.
If they haven't issued the Miranda warning and haven't asked questions, if you make a voluntary utterance
about the crime, it will be admissible.