The marriage relationship gives rise to two distinct privileges in the federal courts. One, the privilege for adverse spousal testimony, allows a party to exclude the adverse testimony of his or her spouse. The other, the privilege for marital communications, protects confidential communications made to one's spouse during the marriage. The privilege for adverse spousal testimony is used primarily in federal criminal procedure, but there is some authority that the privilege for adverse spousal testimony applies to civil actions. The modern justification for the privilege for adverse spousal testimony is the encouragement of harmony and peace in the marital relationship.
James Quimby Wallace III, Federal Criminal Procedure - Privilege for Adverse Spousal Testimony Vested in Witness Spouse, 3 Campbell L. Rev. 125 (1981).