The marital testimony privilege -- the adverse spousal testimony privilege -- can be waived.

Fed. R. Evid. 801(d)(1)(B) ("A statement is not hearsay if-- ... (1) Prior statement by witness. The declarant testifies at the trial or hearing and is subject to cross-examination concerning the statement, and the statement is ... (B) consistent with the declarant's testimony and is offered to rebut an express or implied charge against...A prior statement of a witness is exempt from the prohibition against hearsay evidence if the prior statement is consistent with the witness' testimony at the trial or hearing at which the prior statement is offered, the prior statement is offered to rebut a express or implied charge of recent fabrication or motive, and the witness who made the prior statement testifies and is subject to cross-examination at the trial or hearing at which the prior statement is offered.

Stuart v. UNUM Life Insurance Company of America, 217 F.3d 1145, 1154 (9th Cir. 2000) (holding, in plaintiff employee's action against defendant employer for breach of insurance contract, tortuous breach of insurance contract, and loss of....If some human utterance has legal significance under applicable substantive law and the utterance is offered to establish that a verbal act having such legal significance has taken place, the utterance is not hearsay under Federal Rule of Evidence 801(c) or a "statement" for purposes of Federal Rule of Evidence 801(a)(2) even if the utterance also contains an assertion or appears to contain an an assertion.

United States v. Banks, 405 F.3d 559, 570-571 (7th Cir. 2005) (upholding trial court's admission of witness's testimony about accused's history of storing cocaine in her apartment because it showed that "[accused] had opportunity, knowledge, and intent to store drugs in [witness's] apartment.").Another act, wrong, or crime is not barred by the character evidence rule if it is offered to show ability or opportunity or lack of ability or opportunity to commit a crime or other act, or to show person's presence or absence at scene of crime or elsewhere.