Is there a privilege for marital testimony: is there a privilege against adverse spousal testimony?

Fed. R. Evid. 609(a)(1) (If the witness to be impeached is not a criminal defendant, the admissibility of the conviction is "subject to Rule 403"; if the witness to be impeached is a....If the witness to be impeached is not a criminal defendant, a trial court can exclude a conviction if the opponent shows that, under the standard set forth in Federal Rule of Evidence 403, the risk of prejudice or other harm substantially outweighs the probative value of the conviction; but if the witness to be impeached is a criminal defendant, the trial court must exclude the conviction if the offeror fails to show that the probative value of the conviction on the issue of the truthfulness of the witness (a criminal defendant) outweighs the risk of prejudice to the witness (a criminal defendant).

United States v. Roberts, 887 F.2d 534, 536 (5th Cir. 1989) (affirming conviction for possessing and importing cocaine with intent to distribute despite the trial court's erroneous exclusion of expert's testimony which could have supported accused's claim that he had no intent to violate the law, because...A person's propensity, or character, is not barred by the character rule if it is offered for any purpose other than to show a person's conduct on a particular occasion.

Fed. R. Evid. 405(a) & (b) ("(a) Reputation or opinion. In all cases in which evidence of character or a trait of character of a person is admissible, proof may be made by testimony as to reputation or by testimony in the form of an opinion. On cross-examination, inquiry is allowable into relevant specific instances of conduct. (b)...When an exception to the character evidence prohibition makes evidence of a criminal defedant's character admissible, the testimony of a witness on direct examination about the defendant's character must take the form of reputation or opinion and it cannot consist of specific instances of the defendant's conduct.