In Massachusetts witnesses can often refuse to testify by invoking their Fifth Amendment right against self- incrimination or asserting their marital privilege. When this happens, the prosecutor’s options are severely limited.
According to the Appeals Court:
Whether it is the interspousal privilege or the privilege against self-incrimination which is claimed, if it is clear that a witness for the prosecution will, if called, exercise a privilege not to testify, the witness should not be called or, alternatively, the questions which will cause the privilege to be exercised should not be put in the presence of the jury.
Commonwealth v. Labbe, 6 Mass. App. Ct. 73, 80 (1978)
The same decision suggests that a judge may deny a witness’s attempt to assert either the 5th or the marital privilege, if the prosecutor does not intend to call that person at trial. However, if the prosecutor later decides to use the reluctant witness, a new opportunity to assert should be requested.