The privilege is waived by either the husband or wife going on the witness stand and testifying with the consent of the other spouse. This can be done by the other spouse failing to timely object to the introduction of the other spouse's testimony and the Court then infers a volutary waiver by the remaining spouse. It is important to note that the marital privilege is NOT lost upon the dissolution of the marriage. Even if the parties no longer love one another and would like to see the other former spouse go to jail for the rest of their life, they cannot testify without the consent/waiver of that marital privilege by the other spouse. That's how strong society's interest is in keeping the bonds of matrimony sancrosanct.