The Sixth Commandment, Pt. 1

What does the commandment 'You Shall Not Murder' really mean? Is all killing absolutely forbidden? What about the death penalty, war, or self-defense? Is the commandment solely concerned about killing or are sins of the mind and other forms of violence also involved? How should we apply this commandment to our lives?

NB: There are 4 sermons on the sixth commandment in this series, but the audio for the second sermon on the sixth commandment (pt.2), concerning our duties to others, is currently missing. A link is available to the text however.