Conn. Gen. Stat. § 54-84a: Testimony against spouse.

(a) Except as provided in subsection (b) of this section, in any criminal proceeding, a person may elect or refuse to testify against his or her then lawful spouse.

(b) The testimony of a spouse may be compelled, in the same manner as for any other witness, in a criminal proceeding against the other spouse for (1) joint participation with the spouse in criminal conduct, (2) bodily injury, sexual assault or other violence attempted, committed or threatened upon the spouse, or (3) bodily injury, sexual assault, risk of injury pursuant to section 53-21, or other violence attempted, committed or threatened upon the minor child of either spouse, or any minor child in the care or custody of either spouse.