Is capital punishment scriptural?
Yes. From the earliest scriptures, to those found in the last book, God gives his commandment for capital punishment, when justified. He says in Genesis:
"Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man" (Genesis 9: 6).
Since God is the same yesterday, today and, forever, His opinion of capital punishment for those who take the life of another through the act of murder, has not changed. The thing called "murder" doesn't equate to taking life in the case of defending oneself, or in the act of military war engagements that defend the God-given rights of man. Killing in such instances are even commended throughout the Bible.
The last book in the New Testament maintains God's same attitude about murder. In the following two instances, God sees the followers of Antichrist as murdering God's righteous saints. He prescribes capital punishment for these vile acts.
"And if any man will hurt them, fire proceedeth out of their mouth, and devoureth their enemies: and if any man will hurt them, he must in this manner be killed" (Revelation 11:5).
"He that leadeth into captivity shall go into captivity: he that killeth with the sword must be killed with the sword. Here is the patience and the faith of the saints" (Revelation 13:10).