The significant point is that the moral basis for capital punishment in Genesis is the sanctity of life. The biblical ethic is that because man is endowed with the image of God, his life is so sacred that any malicious destruction of it must be punished by execution. Note that this verse implies that an assault against human life is considered by God an assault against Himself. To murder a person is to attack one who is the image-bearer of God. God regards homicide as an implicit attempt to murder God.
The death penalty mandated in scripture actually affirms the sanctity of life.
