Everyone has a different opinion of Karma. I feel that in some cases people have stolen our lives and we are even as the living dead. When we put a death spell on someone, which is what this sounds like, I think it depends on Justice to make the final decision. If someone has been living a life of domestic violence for a certain amount of time, he or she may feel the consequences are worth while.
This Euthanasia Spell sounds more like an attempt on someone's life. I would use extreme caution. One never knows what path is ahead due to one's actions. Careful even with getting permission. I have horror stories of spells gone awry even after gaining permission.