In God's sight the lives of the unborn are to be more valued as they have not yet had an opportunity to develop a direction of relationship with Him. Punishment following conviction for a crime is in the hands of legitimate authorities. Do not think that I have come to bring peace upon the earth. Jesus' admonishment of Simon bar Jonah was due to his failure to distinguish between proper and improper usages of the sword. Simon had both failed to understand the prophesy of Jesus regarding His death and failed to recognize the long term spiritual value of the arrest and ultimate death of Jesus.
Murder is the willful taking of innocent human life .
It seems apparent that the translators of the NRSV recognized the proper meaning of the commandment and relegated the literal translation of the word to a footnote. Killing has the broader concept of taking the life of any human being whether innocent or guilty. A person who kills in defense of himself or another innocent human being acts righteously. A person who is about to take the life of an innocent human being is to be defended against in whatever way is deemed necessary for surety of protection. The impetus for defensive action is even greater when a known, practicing, publicly unrepentant murderer of innocent people is at hand.