By the law is knowledge of sin (Romans 3:19).
I would not have known sin except through the law (Romans 7:7).
It is the law that reveals what is sin leading to death? (see listed below)
These were the judgements of God given to Moses by which Israel was to be judged. These accusations had to be established before three witnesses for it to stand. And the earthly government was to execute the wrath of God on earth (Rom. 13:4) against those who practice evil.
So if God's judgement is that those guilty of such be put to death,
John may well be saying to not pray or expect for God to deliver those who have committed such sins punishable by death, to be delivered from the righteous judgement of the judicial system on earth. This would not be inconsistent with Paul's instruction regarding the one in sexual immorality "deliver such a one to Satan for the destruction of the flesh, that his spirit may be saved in the day of the Lord Jesus." (1 Cor. 5:5).
Christians would not pray nor expect God to deliver such a one from death row. But such an one could be saved in the day of the Lord.
HERE IS A LIST OF SINS THAT ACCORDING TO THE LAW LEAD TO DEATH:
(Segments in blue are exceptions)
Leviticus 20:2--whoever gives his descendants to Molech shall be put to death
Leviticus 20:9--Whoever curses his father or his mother shall surely be put to death.
Leviticus 20:10--The man who commits adultery with a man's wife he who commits adultery with his neighbor's wife, the adulterer and the adulteress, shall surely be put to death.
Leviticus 20:11--The man who lies with his father's wife has uncovered his father's nakedness; both of them shall surely be put to death.
Leviticus 20:12--If a man lies with his daughter-in-law, both of them shall surely be put to death.
Leviticus 20:13--If a man lies with a male as he lies with a woman, both of them have committed an abomination. They shall surely be put to death.
Leviticus 20:14--If a man marries a woman and her mother, it is wickedness. They shall be burned with fire
Leviticus 20:15--If a man mates with an animal, he shall surely be put to death.
Leviticus 20:16--If a woman approaches any animal and mates with it, you shall kill the woman and the animal. They shall surely be put to death
Leviticus 20:27--A man or a woman who is a medium, or has familiar spirit, shall surely be put to death
Leviticus 24:16--And whoever blasphemes the name of the LORD shall surely be put to death. All the congregation shall certainly stone him, the stranger as well as him who is born in the land. When he blasphemes the name of the LORD, he shall be put to death.
Leviticus 24:17--Whoever kills an man shall surely be put to death.
Leviticus 24:21--whoever kills a man shall be put to death
Leviticus 27:29--No person under the ban, who may become doomed to destruction among men, shall be redeemed, but shall surely be put to death.
Numbers 1:51, 3:10, 3:38, 18;7 The outsider who comes near the tabernacle shall be put to death
Cities of Refuge The manslayer who kills any person accidentally may flee there.
Numbers 35:16 'But if he strikes him with an iron implement, so that he dies, he is a murderer; the murderer shall surely be put to death.
17 And if he strikes him with a stone in the hand, by which one could die, and he does die, he is a murderer; the murderer shall surely be put to death.
18 Or if he strikes him with a wooden hand weapon, by which one could die, and he does die, he is a murderer; the murderer shall surely be put to death.
19 The avenger of blood himself shall put the murderer to death; when he meets him, he shall put him to death.
20 If he pushes him out of hatred or, while lying in wait, hurls something at him so that he dies,21 or in enmity he strikes him with his hand so that he dies, the one who struck him shall surely be put to death.
25 So the congregation shall deliver the manslayer from the hand of the avenger of blood, and the congregation shall return him to the city of refuge where he had fled, and he shall remain there until the death of the high priest who was anointed with the holy oil.26 But if the manslayer at any time goes outside the limits of the city of refuge where he fled,27 and the avenger of blood finds him outside the limits of his city of refuge, and the avenger of blood kills the manslayer, he shall not be guilty of blood,28 because he should have remained in his city of refuge until the death of the high priest. But after the death of the high priest the manslayer may return to the land of his possession.
29 'And these things shall be a statute of judgment to you throughout your generations in all your dwellings.
30 Whoever kills a person, the murderer shall be put to death on the testimony of witnesses; but one witness is not sufficient testimony against a person for the death penalty.
31 Moreover you shall take no ransom for the life of a murderer who is guilty of death, but he shall surely be put to death.
32 And you shall take no ransom for him who has fled to his city of refuge, that he may return to dwell in the land before the death of the priest.
33 So you shall not pollute the land where you are; for blood defiles the land, and no atonement can be made for the land, for the blood that is shed on it, except by the blood of him who shed it.
34 Therefore do not defile the land which you inhabit, in the midst of which I dwell; for I the LORD dwell among the children of Israel.' "
Deuteronomy13:5 But that prophet or that dreamer of dreams shall be put to death, because he has spoken in order to turn you away from the LORD your God, who brought you out of the land of Egypt and redeemed you from the house of bondage, to entice you from the way in which the LORD your God commanded you to walk. So you shall put away the evil from your midst.
Deuteronomy 13:6 "If your brother, the son of your mother, your son or your daughter, the wife of your bosom, or your friend who is as your own soul, secretly entices you, saying, 'Let us go and serve other gods,' which you have not known, neither you nor your fathers,7 of the gods of the people which are all around you, near to you or far off from you, from one end of the earth to the other end of the earth,8 you shall not consent to him or listen to him, nor shall your eye pity him, nor shall you spare him or conceal him;9 but you shall surely kill him; your hand shall be first against him to put him to death . . .