Just in case questions arise about the morality involved, I wished to put some detailed answers here about human life and Catholic morals, “just a click away.”
The Catholic tradition labels the commandment “thou shalt not kill” as the fifth in the Decalogue (#5 of 10). To clarify all the moral implications that Catholics understand as essential to this commandment, we cannot do any better than reference the Catechism of the Catholic Church.
You can find the Catechism’s full section on the fifth commandment here.
Some appropriate sections are included here, with emphasis added for the part in bold.
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(CDF, instruction, Donum vitae, intro. 5.)
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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(St. Thomas Aquinas, STh II-II,64,7, corp. art.)
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2268 The fifth commandment forbids direct and intentional killing as gravely sinful. The murderer and those who cooperate voluntarily in murder commit a sin that cries out to heaven for vengeance.
Infanticide, fratricide, parricide, and the murder of a spouse are especially grave crimes by reason of the natural bonds which they break. Concern for eugenics or public health cannot justify any murder, even if commanded by public authority.
2269 The fifth commandment forbids doing anything with the intention of indirectly bringing about a person’s death. The moral law prohibits exposing someone to mortal danger without grave reason, as well as refusing assistance to a person in danger.
The acceptance by human society of murderous famines, without efforts to remedy them, is a scandalous injustice and a grave offense. Those whose usurious and avaricious dealings lead to the hunger and death of their brethren in the human family indirectly commit homicide, which is imputable to them.
Unintentional killing is not morally imputable. But one is not exonerated from grave offense if, without proportionate reasons, he has acted in a way that brings about someone’s death, even without the intention to do so.2270 Human life must be respected and protected absolutely from the moment of conception. From the first moment of his existence, a human being must be recognized as having the rights of a person – among which is the inviolable right of every innocent being to life.72(Cf. CDF, Donum vitae I,1.)
Before I formed you in the womb I knew you, and before you were born I consecrated you.73(Jer 1:5; cf. Job10:8-12; PsaIm 22:10-11)
My frame was not hidden from you, when I was being made in secret, intricately wrought in the depths of the earth.74(Ps 139:15)…
2273 The inalienable right to life of every innocent human individual is a constitutive element of a civil society and its legislation:
“The inalienable rights of the person must be recognized and respected by civil society and the political authority. These human rights depend neither on single individuals nor on parents; nor do they represent a concession made by society and the state; they belong to human nature and are inherent in the person by virtue of the creative act from which the person took his origin. Among such fundamental rights one should mention in this regard every human being’s right to life and physical integrity from the moment of conception until death.”80(CDF, Donum vitae III)
“The moment a positive law deprives a category of human beings of the protection which civil legislation ought to accord them, the state is denying the equality of all before the law. When the state does not place its power at the service of the rights of each citizen, and in particular of the more vulnerable, the very foundations of a state based on law are undermined. . . . As a consequence of the respect and protection which must be ensured for the unborn child from the moment of conception, the law must provide appropriate penal sanctions for every deliberate violation of the child’s rights.”81(CDF, Donum vitae III.…
2277 Whatever its motives and means, direct euthanasia consists in putting an end to the lives of handicapped, sick, or dying persons. It is morally unacceptable.
Thus an act or omission which, of itself or by intention, causes death in order to eliminate suffering constitutes a murder gravely contrary to the dignity of the human person and to the respect due to the living God, his Creator. The error of judgment into which one can fall in good faith does not change the nature of this murderous act, which must always be forbidden and excluded.2280 Everyone is responsible for his life before God who has given it to him. It is God who remains the sovereign Master of life. We are obliged to accept life gratefully and preserve it for his honor and the salvation of our souls. We are stewards, not owners, of the life God has entrusted to us. It is not ours to dispose of.
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2319 Every human life, from the moment of conception until death, is sacred because the human person has been willed for its own sake in the image and likeness of the living and holy God.
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2323 Because it should be treated as a person from conception, the embryo must be defended in its integrity, cared for, and healed like every other human being.
2324 Intentional euthanasia, whatever its forms or motives, is murder. It is gravely contrary to the dignity of the human person and to the respect due to the living God, his Creator.
2325 Suicide is seriously contrary to justice, hope, and charity. It is forbidden by the fifth commandment.
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2327 Because of the evils and injustices that all war brings with it, we must do everything reasonably possible to avoid it. The Church prays: “From famine, pestilence, and war, O Lord, deliver us.”
2328 The Church and human reason assert the permanent validity of the moral law during armed conflicts. Practices deliberately contrary to the law of nations and to its universal principles are crimes.
2329 “The arms race is one of the greatest curses on the human race and the harm it inflicts on the poor is more than can be endured” (GS 81 § 3).
2330 “Blessed are the peacemakers, for they shall be called sons of God” (Mt 5:9).
Ubi Petrus VT 