A Message from Pope John Paul II
".............Certainly, the intrinsic value of life and the duty to love oneself no less than others are the basis of a true right to self-defense ... legitimate defense can be not only a right but a grave duty for someone responsible for another's life, the common good of the family or of the State. Unfortunately, it happens that the need to render the aggressor incapable of causing harm sometimes involves taking his life. In this case, the fatal outcome is attributable to the aggressor whose actions brought it about, even though he may not be morally responsible because of a lack of the use of reason."
- Pope John Paul II, Encyclical Letter from 1995, EVANGELIUM VITAE