It's always been possible, and frequent. People have had innumerable conversations relevant to criminal intent, and refused to divulge information on them. The

It's always been possible, and frequent. People have had innumerable conversations relevant to criminal intent, and refused to divulge information on them. The founders were certainly aware of that when the Fifth Amendment was added to the constitution. It was the development of telephone communication, and warrants for wiretapping, that first made such private communications accessible to the government.