Justice Samuel Blatchford (unanimous): “It is impossible that the meaning of the constitutional provision can only be that a person shall not be compelled to be a witness against himself in a criminal prosecution against himself. It would doubtless cover such cases; but it is not limited to them. The object was to insure that a person should not be compelled, when acting as a witness in any investigation, to give testimony which might tend to show that he himself had committed a crime. The privilege is limited to criminal matters, but it is as broad as the mischief against which it seeks to guard.”