Spousal Immunity and Marital Communications

“Anyone could see that an absolute privilege in a husband to close the mouth of the wife in testimony against him would be a vested license to injure her in secret with complete immunity….If the promotion of marital peace, and the apprehension of marital dissension, are the ultimate ground of the privilege, it is an overgenerous assumption that the wife who has been beaten, poisoned, or deserted is still on such terms of delicate good feeling with her spouse that her testimony must not be enforced lest the iridescent halo of peace be dispelled by the breath of disparaging testimony. And if there were, conceivably, any such peace, would it be a peace such as the law could desire to protect? Could it be any other peace than that which the tyrant secures for himself by oppression? And could the law pretend to regard the effect produced by a wife's testimony in her own redress as being worth consideration on behalf of a husband who has already grossly violated his marital duties? If there had been any reason at all for the privilege, that reason surely fell away in such cases."

— John Henry Wigmore, 8 Wigmore on Evidence §2239 at 243 (McNaughton Rev. 1961).

Two distinct doctrines historically prevented compelled testimony of one spouse against the other: spousal immunity (aka adverse testimony privilege) and the marital communication privilege.  These privileges are recognized under Federal Rule of Evidence 501 and state laws.