Many a misguided believer or critic who opposes the death penalty will quote the well known sixth commandment, “Thou shalt not kill” (Exodus 20:13Thou shalt not kill.
See All...) as the basis for their argument. However, most do not realize that the same God who commanded us not to kill (outside of defending oneself Exodus 22:2If a thief be found breaking up, and be smitten that he die, there shall no blood be shed for him.
See All...) esteemed the value of human life in such high regard that He established the very law they oppose as a deterrent to murder.

This law is the basic tenant on which all of man’s civil laws are based (the righteous punishment of evil doers) and is the very foundation by which the governing bodies of mankind are to rule.

Before the Law

Genesis 9:5-6 [5] And surely your blood of your lives will I require; at the hand of every beast will I require it, and at the hand of man; at the hand of every man's brother will I require the life of man. [6] Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.
See All...  And surely your blood of your lives will I require; at the hand of every beast will I require it, and at the hand of man; at the hand of every man's brother will I require the life of man. Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.

Under the Law

Numbers 35:30-31 [30] Whoso killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person to cause him to die. [31] Moreover ye shall take no satisfaction for the life of a murderer, which is guilty of death: but he shall be surely put to death.
See All... Whoso killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person to cause him to die. Moreover ye shall take no satisfaction for the life of a murderer, which is guilty of death: but he shall be surely put to death.

Exodus 21:12He that smiteth a man, so that he die, shall be surely put to death.
See All...  He that smiteth a man, so that he die, shall be surely put to death.

(See also Leviticus 24:17And he that killeth any man shall surely be put to death.
See All..., Numbers 35:16And if he smite him with an instrument of iron, so that he die, he is a murderer: the murderer shall surely be put to death.
See All..., Proverbs 28:17A man that doeth violence to the blood of any person shall flee to the pit; let no man stay him.
See All...)

Under Grace

Under grace in the New Testament this same authority is still given to magistrates and governing authorities in which Paul says we are to be subject to in obedience to God.

Romans 13:1-5 [1] Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God. [2] Whosoever therefore resisteth the power, resisteth the ordinance of God: and they that resist shall receive to themselves damnation. [3] For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same: [4] For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil. [5] Wherefore ye must needs be subject, not only for wrath, but also for conscience sake.
See All... Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God. Whosoever therefore resisteth the power, resisteth the ordinance of God: and they that resist shall receive to themselves damnation. For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same: For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil. Wherefore ye must needs be subject, not only for wrath, but also for conscience sake.

1Peter 2:13-14 [13] Submit yourselves to every ordinance of man for the Lord's sake: whether it be to the king, as supreme; [14] Or unto governors, as unto them that are sent by him for the punishment of evildoers, and for the praise of them that do well.
See All... Submit yourselves to every ordinance of man for the Lord's sake: whether it be to the king, as supreme; Or unto governors, as unto them that are sent by him for the punishment of evildoers, and for the praise of them that do well.

Which Paul himself willingly submitted to:

Acts 25:10-11 [10] Then said Paul, I stand at Caesar's judgment seat, where I ought to be judged: to the Jews have I done no wrong, as thou very well knowest. [11] For if I be an offender, or have committed any thing worthy of death, I refuse not to die: but if there be none of these things whereof these accuse me, no man may deliver me unto them. I appeal unto Caesar.
See All... Then said Paul, I stand at Caesar's judgment seat, where I ought to be judged: to the Jews have I done no wrong, as thou very well knowest. For if I be an offender, or have committed any thing worthy of death, I refuse not to die: but if there be none of these things whereof these accuse me, no man may deliver me unto them. I appeal unto Caesar.

Even unlearned barbarians and lost Gentile rulers understood the basic premise of capitol punishment for the offense of murder – Acts 28:1-4 [1] And when they were escaped, then they knew that the island was called Melita. [2] And the barbarous people shewed us no little kindness: for they kindled a fire, and received us every one, because of the present rain, and because of the cold. [3] And when Paul had gathered a bundle of sticks, and laid them on the fire, there came a viper out of the heat, and fastened on his hand. [4] And when the barbarians saw the venomous beast hang on his hand, they said among themselves, No doubt this man is a murderer, whom, though he hath escaped the sea, yet vengeance suffereth not to live.
See All..., Acts 25:16To whom I answered, It is not the manner of the Romans to deliver any man to die, before that he which is accused have the accusers face to face, and have licence to answer for himself concerning the crime laid against him.
See All....

God-Given Instinct

In fact, it is this God-given maternal instinct of man to judge that testifies to the fact that there is a Holy God and that He requires righteousness and punishment for evil. John 1:9That was the true Light, which lighteth every man that cometh into the world.
See All..., Romans 1:29-32 [29] Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers, [30] Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents, [31] Without understanding, covenantbreakers, without natural affection, implacable, unmerciful: [32] Who knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them.
See All..., 2:1-16 [1] I will stand upon my watch, and set me upon the tower, and will watch to see what he will say unto me, and what I shall answer when I am reproved. [2] And the LORD answered me, and said, Write the vision, and make it plain upon tables, that he may run that readeth it. [3] For the vision is yet for an appointed time, but at the end it shall speak, and not lie: though it tarry, wait for it; because it will surely come, it will not tarry. [4] Behold, his soul which is lifted up is not upright in him: but the just shall live by his faith. [5] Yea also, because he transgresseth by wine, he is a proud man, neither keepeth at home, who enlargeth his desire as hell, and is as death, and cannot be satisfied, but gathereth unto him all nations, and heapeth unto him all people: [6] Shall not all these take up a parable against him, and a taunting proverb against him, and say, Woe to him that increaseth that which is not his! how long? and to him that ladeth himself with thick clay! [7] Shall they not rise up suddenly that shall bite thee, and awake that shall vex thee, and thou shalt be for booties unto them? [8] Because thou hast spoiled many nations, all the remnant of the people shall spoil thee; because of men's blood, and for the violence of the land, of the city, and of all that dwell therein. [9] Woe to him that coveteth an evil covetousness to his house, that he may set his nest on high, that he may be delivered from the power of evil! [10] Thou hast consulted shame to thy house by cutting off many people, and hast sinned against thy soul. [11] For the stone shall cry out of the wall, and the beam out of the timber shall answer it. [12] Woe to him that buildeth a town with blood, and stablisheth a city by iniquity! [13] Behold, is it not of the LORD of hosts that the people shall labour in the very fire, and the people shall weary themselves for very vanity? [14] For the earth shall be filled with the knowledge of the glory of the LORD, as the waters cover the sea. [15] Woe unto him that giveth his neighbour drink, that puttest thy bottle to him, and makest him drunken also, that thou mayest look on their nakedness! [16] Thou art filled with shame for glory: drink thou also, and let thy foreskin be uncovered: the cup of the LORD's right hand shall be turned unto thee, and shameful spewing shall be on thy glory.
See All....

When convicted murderers are allowed to live and the innocent blood of their victims is not avenged the Lord warns that the governing authorities are now guilty themselves of this blood. This has a twofold negative effect on a land and its citizens. First without the deterrent that the death penalty imposes there is less restraint on evil doers and thus there is an increase and boldness in their sin. Next, the Bible says that the land then becomes physically and spiritually polluted by these increased transgressions and the shed blood which in turn invites God’s judgment on that nation. The Bible describes this moral and spiritual breakdown in a civilization as having “no fear of God” (Genesis 20:11And Abraham said, Because I thought, Surely the fear of God is not in this place; and they will slay me for my wife's sake.
See All..., Psalm 36:1The transgression of the wicked saith within my heart, that there is no fear of God before his eyes.
See All..., Romans 3:18There is no fear of God before their eyes.
See All...). Is it any wonder then that in America one of the more popular secular phrases used today in advertising (No Fear!) is the description given for a lawless society? Also please note how that the Lord makes no allowances for plea bargaining for the life of the murderer, as his blood is the only acceptable atonement for the shed blood of his victim.

Deuteronomy 19:10-13 [10] That innocent blood be not shed in thy land, which the LORD thy God giveth thee for an inheritance, and so blood be upon thee. [11] But if any man hate his neighbour, and lie in wait for him, and rise up against him, and smite him mortally that he die, and fleeth into one of these cities: [12] Then the elders of his city shall send and fetch him thence, and deliver him into the hand of the avenger of blood, that he may die. [13] Thine eye shall not pity him, but thou shalt put away the guilt of innocent blood from Israel, that it may go well with thee.
See All... That innocent blood be not shed in thy land, which the LORD thy God giveth thee for an inheritance, and so blood be upon thee. But if any man hate his neighbour, and lie in wait for him, and rise up against him, and smite him mortally that he die, and fleeth into one of these cities: Then the elders of his city shall send and fetch him thence, and deliver him into the hand of the avenger of blood, that he may die. Thine eye shall not pity him, but thou shalt put away the guilt of innocent blood from Israel, that it may go well with thee.

Numbers 35:30-31 [30] Whoso killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person to cause him to die. [31] Moreover ye shall take no satisfaction for the life of a murderer, which is guilty of death: but he shall be surely put to death.
See All... Whoso killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person to cause him to die. Moreover ye shall take no satisfaction for the life of a murderer, which is guilty of death: but he shall be surely put to death.

Numbers 35:33So ye shall not pollute the land wherein ye are: for blood it defileth the land: and the land cannot be cleansed of the blood that is shed therein, but by the blood of him that shed it.
See All... So ye shall not pollute the land wherein ye are: for blood it defileth the land: and the land cannot be cleansed of the blood that is shed therein, but by the blood of him that shed it.

Hosea 4:2-3 [2] By swearing, and lying, and killing, and stealing, and committing adultery, they break out, and blood toucheth blood. [3] Therefore shall the land mourn, and every one that dwelleth therein shall languish, with the beasts of the field, and with the fowls of heaven; yea, the fishes of the sea also shall be taken away.
See All... By swearing, and lying, and killing, and stealing, and committing adultery, they break out, and blood toucheth blood. Therefore shall the land mourn, and every one that dwelleth therein shall languish, with the beasts of the field, and with the fowls of heaven; yea, the fishes of the sea also shall be taken away.

Conclusion

An interesting side note to this study is that before the flood the Lord says the outstanding characteristic of the Earth was that it was filled with violence (Genesis 6:11-13 [11] The earth also was corrupt before God, and the earth was filled with violence. [12] And God looked upon the earth, and, behold, it was corrupt; for all flesh had corrupted his way upon the earth. [13] And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth.
See All...). We can safely assume then that murder was probably prevalent at that time which would have met an abundance of blood shed with the land becoming increasingly polluted. This unavenged blood and resulting pollution may have been why the Lord chose to destroy the entire planet and not just all of mankind. This seems even more feasible in light of the fact that capitol punishment was instituted by the Lord to Noah and his sons directly following the flood (Genesis 9:1-6 [1] And God blessed Noah and his sons, and said unto them, Be fruitful, and multiply, and replenish the earth. [2] And the fear of you and the dread of you shall be upon every beast of the earth, and upon every fowl of the air, upon all that moveth upon the earth, and upon all the fishes of the sea; into your hand are they delivered. [3] Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things. [4] But flesh with the life thereof, which is the blood thereof, shall ye not eat. [5] And surely your blood of your lives will I require; at the hand of every beast will I require it, and at the hand of man; at the hand of every man's brother will I require the life of man. [6] Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.
See All...).