Thus murder shows contempt for God as well as for one's fellow man. Obviously, as suggested by the principles of justice as seen in the Old Testament, capital punishment should only be carried out after clear evidence and by a just court. This is an excellent biblical web site, which deals with a lot of social issues. The following is taken from an article in the book, The Bible Has the Answer , by Henry Morris and Martin Clark, Creation Life Publishers. I'm sure it will help.
Capital punishment is such a duty.
The Christian's final authority in all matters of faith and practice is not public opinion, but the Bible, God's Holy Word. Moses governed Israel with a set of God-given laws, the most familiar of which are the Ten Commandments. Certain laws, such as dietary, civil and ceremonial prescriptions were meant for the Hebrew nation during a particular part of its history. The Bible, however, shows that capital punishment for murder is of a different order than that prescribed under the civil law that governed Old Testament Israel. Following the worldwide Flood, God gave a covenant to Noah, graciously promising never again to send His judgment as a mammoth flood.