When assessing the relationship between spouses and common-law partners, officers must be satisfied that the relationship that exists is genuine. That's irrelevant of which country the application is being processed from.
The application kit requires that the applicants submit certain documents as proof of their relationship. That could include things such as pictures and things of that nature.
In the case of applicants in the spouse or common-law partner in Canada class, officers must also be satisfied that the applicant is living with the sponsor in Canada.
If documents submitted do not provide adequate proof of that genuine conjugal relationship within the context of a marriage or common-law relationship, or if officers doubt that the applicant is living with the sponsor, for example, an officer may again request additional information or schedule an interview to be able to confirm the genuineness of the relationship.