There are numerous biblical passages, as well as theological teachings obviously supportive of the civil governments imposition of the death penalty.

Jesus: “So Pilate said to (Jesus), “Do you not speak to me? Do you not know that I have power to release you and I have power to crucify you?” Jesus answered (him), “You would have no power over me if it had not been given to you from above.” John 19:10-11
Saint Paul, in his hearing before Festus, states: “if then I am a wrong doer, and have committed anything worthy of death, I do not refuse to die.” Acts 25:11.

St. Augustine: “The same divine law which forbids the killing of a human being allows certain exceptions. Since the agent of authority is but a sword in the hand, and is not responsible for the killing, it is in no way contrary to the commandment “Thou shalt not kill”, for the representative of the State’s authority to put criminals to death, according to the Law or the rule of rational justice.” The City of God, Book 1, Chapter 21

St. Thomas Aquinas finds all biblical interpretations against executions “frivolous”, citing Exodus 22:18, “wrongdoers thou shalt not suffer to live”. Unequivocally, he states,” The civil rulers execute, justly and sinlessly, pestiferous men in order to protect the peace of the state.” (Summa Contra Gentiles, III, 146

St. Thomas Aquinas: “The fact that the evil, as long as they live, can be corrected from their errors does not prohibit the fact that they may be justly executed, for the danger which threatens from their way of life is greater and more certain than the good which may be expected from their improvement. They also have at that critical point of death the opportunity to be converted to God through repentance. And if they are so stubborn that even at the point of death their heart does not draw back from evil, it is possible to make a highly probable judgement that they would never come away from evil to the right use of their powers.” Summa Contra Gentiles, Book III, 146.

Saints Thomas Aquinas and Augustine. In addition to the required punishment for murder and the deterrence standards, both Saints find that executing murderers is also an act of charity and mercy. Saint Augustine confirms that ” . . . inflicting capital punishment . . . protects those who are undergoing capital punishment from the harm they may suffer . . . through increased sinning which might continue if their life went on.” (On the Lord’s Sermon, 1.20.63-64.)

Saint Thomas Aquinas finds that ” . . . the death inflicted by the judge profits the sinner, if he be converted, unto the expiation of his crime; and, if he be not converted, it profits so as to put an end to the sin, because the sinner is thus deprived of the power to sin anymore.” (Summa Theologica, II-II, 25, 6 ad 2.)

St. Thomas Aquinas: “If a man is a danger to the community, threatening it with disintegration by some wrongdoing of his, then his execution for the healing and preservation of the common good is to be commended. Only the public authority, not private persons, may licitly execute malefactors by public judgement. Men shall be sentenced to death for crimes of irreparable harm or which are particularly perverted.” Summa Theologica, 11; 65-2; 66-6.

Saint (& Pope) Pius V, “The just use of (executions), far from involving the crime of murder, is an act of paramount obedience to this (Fifth) Commandment which prohibits murder.” “The Roman Catechism of the Council of Trent” (1566).

Pope Pius XII: “When it is a question of the execution of a man condemned to death it is then reserved to the public power to deprive the condemned of the benefit of life, in expiation of his fault, when already, by his fault, he has dispossessed himself of the right to live.” 9/14/52.