The use of deadly force is not one to be taken lightly. I for one hope I never have to know what its like to use it. In Wisconsin (a criminal friendly state) if you shoot someone even in your own home you will have to prove that you did so in self defence. No castle doctrine here. We are not given the "privilege" of self defence. We also (because of no castle doctrine) have to be concerned about the civil action taken by the family of the criminal. It is a sad fact that the family can sue you for killing their precious relative while they areattempting to kill you.
I am sure others will add to this, but that is why the legal repercussions are a major concern.