When a person is asked to appear in court to testify against their spouse, they by law do not have to. If a person wishes to testify against their spouse, they are free to do as they please. The marital confidence privilege however, is a privilege which can be used when they are asked to undergo in testifying against their spouse. The marital confidence privilege can be used in civil and criminal court cases.
If a person chooses to use this privilege instead of testifying against their spouse they must fall under two requirements: first, no one else could have been located near the married couple during the time that is in question, and secondly, both members in the marriage agree that the communication was confidential. This rule can also be used in court if an opposing party member asks to speak to speak to a spouse regarding any topic, whether it is related to the case or not.