Custody has a somewhat nebulous definition. Any time one is not free to leave they are obviously in custody. The problem is, and has been increased by court decisions, when a person believes they are not free to leave is not always accepted as being in custody. That is a perfect example of my point that a typical person often is not aware of their rights and as such, unwittingly relinquishes them.Understand that questioning is a fundamental part of police work. Miranda only cuts in when the person is already in custody. A good deal of fruitful police interrogation happens in consensual situations where Miranda warnings aren't required.