Generally spouses are barred from testifying against one another. However, there are many exceptions to this rule. RCW 5.60.060 Sets out the following:
Who is disqualified—Privileged communications. (1) A spouse or domestic partner shall not be examined for or against his or her spouse or domestic partner, without the consent of the spouse or domestic partner; nor can either during marriage or during the domestic partnership or afterward, be without the consent of the other, examined as to any communication made by one to the other during the marriage or the domestic partnership.
Here come the exceptions:
But this exception shall not apply to a civil action or proceeding by one against the other, nor to a criminal action or proceeding for a crime committed by one against the other, nor to a criminal action or proceeding against a spouse or domestic partner if the marriage or the domestic partnership occurred subsequent to the filing of formal charges against the defendant, nor to a criminal action or proceeding for a crime committed by said spouse or domestic partner against any child of whom said spouse or domestic partner is the parent or guardian, nor to a proceeding under chapter 71.05 or 71.09 RCW: PROVIDED, That the spouse or the domestic partner of a person sought to be detained under chapter 71.05 or 71.09 RCW may not be compelled to testify and shall be so informed by the court prior to being called as a witness.
Keep in mind that the privilege must be claimed at trial or it otherwise waived. Also, statements may be admitted if revealed to a third party before trial. business agreements and property transactions because those may not be privileged either. As always, talk to an attorney first before communicating with anyone about your case.