THE FIFTH COMMANDMENT
You shall not kill.54 You have heard that it was said to the men of old, “You shall not kill: and whoever kills shall be liable to judgment.” But I say to you that every one who is angry with his brother shall be liable to judgment.55
2258 "Human life is sacred because from its beginning it involves the creative action of God and it remains for ever in a special relationship with the Creator, who is its sole end. God alone is the Lord of life from its beginning until its end: no one can under any circumstance claim for himself the right directly to destroy an innocent human being."56
I. RESPECT FOR HUMAN LIFE
The witness of sacred history
2259 In the account of Abel’s murder by his brother Cain,57 Scripture reveals the presence of anger and envy in man, consequences of original sin, from the beginning of human history. Man has become the enemy of his fellow man. God declares the wickedness of this fratricide: "What have you done? The voice of your brother’s blood is crying to me from the ground. And now you are cursed from the ground, which has opened its mouth to receive your brother’s blood from your hand."58
2260 The covenant between God and mankind is interwoven with reminders of God’s gift of human life and man’s murderous violence:
For your lifeblood I will surely require a reckoning. . . . Whoever sheds the blood of man, by man shall his blood be shed; for God made man in his own image.59 The Old Testament always considered blood a sacred sign of life.60 This teaching remains necessary for all time.
2261 Scripture specifies the prohibition contained in the fifth commandment: "Do not slay the innocent and the righteous."61 The deliberate murder of an innocent person is gravely contrary to the dignity of the human being, to the golden rule, and to the holiness of the Creator. The law forbidding it is universally valid: it obliges each and everyone, always and everywhere.
2262 In the Sermon on the Mount, the Lord recalls the commandment, "You shall not kill,"62 and adds to it the proscription of anger, hatred, and vengeance. Going further, Christ asks his disciples to turn the other cheek, to love their enemies.63 He did not defend himself and told Peter to leave his sword in its sheath.64
Legitimate defense
2263 The legitimate defense of persons and societies is not an exception to the prohibition against the murder of the innocent that constitutes intentional killing. "The act of self-defense can have a double effect: the preservation of one’s own life; and the killing of the aggressor. . . . The one is intended, the other is not."65
2264 Love toward oneself remains a fundamental principle of morality. Therefore it is legitimate to insist on respect for one’s own right to life. Someone who defends his life is not guilty of murder even if he is forced to deal his aggressor a lethal blow:
If a man in self-defense uses more than necessary violence, it will be unlawful: whereas if he repels force with moderation, his defense will be lawful. . . . Nor is it necessary for salvation that a man omit the act of moderate self-defense to avoid killing the other man, since one is bound to take more care of one’s own life than of another’s.66 2265 Legitimate defense can be not only a right but a grave duty for one who is responsible for the lives of others. The defense of the common good requires that an unjust aggressor be rendered unable to cause harm. For this reason, those who legitimately hold authority also have the right to use arms to repel aggressors against the civil community entrusted to their responsibility.
2266 The efforts of the state to curb the spread of behavior harmful to people’s rights and to the basic rules of civil society correspond to the requirement of safeguarding the common good. Legitimate public authority has the right and duty to inflict punishment proportionate to the gravity of the offense. Punishment has the primary aim of redressing the disorder introduced by the offense. When it is willingly accepted by the guilty party, it assumes the value of expiation. Punishment then, in addition to defending public order and protecting people’s safety, has a medicinal purpose: as far as possible, it must contribute to the correction of the guilty party.67
2267 Assuming that the guilty party’s identity and responsibility have been fully determined, the traditional teaching of the Church does not exclude recourse to the death penalty, if this is the only possible way of effectively defending human lives against the unjust aggressor.
If, however, non-lethal means are sufficient to defend and protect people’s safety from the aggressor, authority will limit itself to such means, as these are more in keeping with the concrete conditions of the common good and more in conformity to the dignity of the human person.
Today, in fact, as a consequence of the possibilities which the state has for effectively preventing crime, by rendering one who has committed an offense incapable of doing harm - without definitely taking away from him the possibility of redeeming himself - the cases in which the execution of the offender is an absolute necessity "are very rare, if not practically nonexistent."68
