In United States v. Morris, 988 F.2d 1335, 1337 (4th Cir. 1993), the court held that it was reversible error for a prosecutor to ask the defendant's wife, who was testifying as a defense witness at trial, about the fact that she had claimed the spousal adverse testimony privilege when called to testify before the grand jury.
Observing that, while the privilege is not constitutionally based, "marital silence offers the same protection as does Fifth Amendment silence," id. at 1339, the court reasoned that "the inference that a wife remained silent before the grand jury because she knew information that would inculpate her husband is one the jury is likely to draw." Id. at 1340.
The court explained:
The prosecutor's cross-examination of the defendant's wife about her invocation of the privilege is bound to have had as a purpose to infer that she would have testified before the grand jury if she had something exculpatory to say. To permit such an inference would destroy the privilege. Id. at 1341.