Q: Will the spell backfire or come back onto me in any way?
A: I don’t believe in magic backfiring; but if you do, then this answer is up to you to decide.
It also has its own page about Black Magic and Karma:
Hoodoo is an old-fashioned style of magic, known by many names including conjure and voodoo. While hoodoo does share some common origins with the religion of Voudou (Voodoo), the two should not be confused. Hoodoo is a type of folk magic, not a religion. It does not require practitioners to be of any certain religion, nor does it require any set rules for living or behaving amongst its followers, other than those behaviors which are done within the rituals themselves. There’s no karma, there’s no rule of three, there’s no black and white/good and bad. Magic is magic and can be used wheresoever it’s needed and howsoever it’s needed. Only the conscience of the practitioners can limit its possible uses.
It is traditional in hoodoo that a person who feels they’ve done wrong may bathe in hyssop to cleanse themselves of their sin.
Hopefully this is adequate to answer the questions of whosoever would seek these magical practices done on their behalf.