[jsprogrammer]

If I understand what you're saying correctly, this happens all the time: for instance, it has happened every time an answering machine tape has been entered into evidence.

No. An answering machine tape is not a person at criminal trial.

> nor shall be compelled in any criminal case to be a witness against himself

You are talking about physical evidence; an answering machine tape, presumably recording some prior conversation, is a physical artifact that already exists. In no way can you construe examining a pre-constructed physical artifact as compelling a criminal defendant to witness against their self [It would imply criminal defendant is somehow the physical artifact itself.].

If I am not mistaken, 'witness' refers to making real claims about events at trial. Making real claims that one performed criminal activities at trial can be construed as evidence. An individual may conceal that evidence by not revealing it, and I don't believe US law allows any way to reveal such evidence.