Writs subpoena (court orders to testify or produce documents) had been part of the English legal system for almost 400 years at the time the Constitution was written. So when the Framers wrote that no one "shall be compelled in any [1] criminal case [2] to be a witness [3] against himself," that's what they meant. Had they intended to limit courts' subpoena power in civil cases, as to non-testimonial conduct, or as to testimony against other people, they would have said so.