Genesis 9

Genesis 9:5-7:
"And from each man, too, I will demand an accounting for the life of his fellow man. Whoever sheds the blood of a man, by man shall his blood be shed; for in the image of God has God made man

The Bible makes it clear what is justly required of those who shed man's (innocent) blood--death. The Bible is pro-capital punishment. Nobody who takes human life seriously could support anything less for premeditated murder. If human life is precious, it is worth protecting; and if it is worth protecting, it is worth executing justice against those who violate it