Idaho Code § 19-3002: Husband and wife as witnesses.

Neither husband nor wife are competent witnesses for or against each other in a criminal action or proceeding to which one or both are parties, except:

1. With the consent of both, or

2. In cases of criminal violence upon one by the other; or acts of physical injury upon a child of either the husband or the wife where the injury has been caused as a result of physical abuse or neglect by one or both of the parents; or to acts or attempted acts of lewd conduct with a minor child; or

3. In cases of desertion or nonsupport of wife or child by the husband.