This combination of death penalty and ransoms will only work effectively in a Christian society. The reason that we can exercise the death penalty is that we are made in the image of God.
Whoever sheds the blood of man, by man shall his blood be shed;The ability to make wise judgements is something that we inherit from God. When a society turns away from God, the image of God is lost, and with that goes the wisdom to make wise judgement. Without the presence of God in their lives the jury may lack the mercy that many situations require. Without the love of God in our hearts, the desire for revenge might overcome us. Justice functions best when the image of God is restored in man through the work of the cross.
for in the image of God has God made man (Gen 9:6).