I believe your original question dealt with the death penalty under the NT dispensation of grace. In this scripture;
1 Timothy 1:9 Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers, The Apostle Paul indicates that the law is for the lawless. IMHO those that commit crimes punishable by death are under the law and therefore are candidates for any punishment rendered under the law.