Spousal Immunity?
At common law a spouse of an accused is incompetent to testify except where the charge involves the person, liberty, or health, of the spouse.[1]
The reason behind this is to support marital harmony.
The Canada Evidence Act was amended in 2015 and the common law rule of spousal incompetency is no longer codified in the Canada Evidence Act. S. 4 (2) now provides: "No person is incompetent, or uncompellable, to testify for the prosecution by reason only that they are married to the accused." ([1]).
Ss. 4 (4) and (5) are no longer in effect.
Thus under the new s. 4 of Canada Evidence Act, spouse of the accused is a competent and compellable witness for the Crown/Prosecution.
https://en.wikibooks.org/wiki/Canadian_Criminal_Evidence/Testimonial_Evidence/Competence_and_Compellability
http://www.criminalnotebook.ca/index.php/Spousal_Immunity