Penalty of Death

After a rather....interesting conversation with my family at dinner, I have to ask a very important question:  are there any Christians who can provide me with a solid, biblically-based argument in support of the death penalty?  Now, again, let me clarify--I want this to be a Christian perspective and one that is biblically, not personally, founded.  This is a major topic of discussion that I have yet to hear a sound rebuttal for.  I know many of us feel strongly about the atrocities that people commit, and many others believe that death is the only penalty suitable for someone who is willing to take a life themselves, but as Christians we are called to a higher standard than just living by what we want to happen.  We are called to live by what God wants to happen.  

My opinion, for a while, has been greatly against the death penalty, and I have yet to hear a strong argument in favor of it.  Though you will most likely not change my stance in this topic (hey, at least I let you know beforehand...), you will provide a strong asset to my understanding of both sides of the topic.  One of my strongest opinions on the topic is that judgement is to be left for God, and so I am seeking to do the same in my understanding of the topic:  to not pass judgment on supporters of the death penalty, but rather to understand where they are coming from to see if the Bible has anything to say in favor of their position.

P.S.  I know the Old Testament has a lot to say about the use of death as a punishment.  I'm looking for what Jesus or the New Testament might say in favor of it.  Remember the New Covenant in your defense please!

P.P.S.  If you are not Christian and still want to weigh in, I'd enjoy hearing your words as well; I'm just really trying to hear a sound biblical presentation for the death penalty.  Thanks!