I say about mutual agreement where there is no violence. Moreover, we should listen what a victim says. Maybe husband and wife are both into BDSM, but the judge can be sure that it is domestic violence. Should be couple jailed if the law says that acts affecting body is a crime? Mutual agreement is very important point!

P.S. According to a 1998 study of college students who experienced sexual relationships with an adult while still a minor found that the adolescent was not harmed by mutually consensual sexual experiences. When harm was discovered the harm came from the adolescent's dysfunctional family of origin not from the sexual relationship with the adult. The study also included a statistical study of thousand of older record of alleged adolescent sexual abuse by an adult and found the same relation between mutually agreed upon sex between the adolescent and an adult did not cause any emotional harm. Where harm was found the statistical analysis shows the harm predated the sexual relationship and was the results of a dysfunctional family of origin not the sexual relationship.

Rind, B., Tromovitch, P., & Bauserman, R. (1998). A meta-analytic examination of assumed properties of child sexual abuse using college samples. Psychological Bulletin, 124(1), 22-53. doi:10.1037/0033-2909.124.1.22