Hopefully I can hop into the conversation soon, but right now I just wanted to put some information up that might be useful to the "Thou shalt not kill" topic at hand.
The hebrew word used for "kill" in the 10 commandments is "rawtsakh." This specific word is used only 3 other times in the OT and 1 of those 3 times is in the second rendering of the 10 commandments. The word's definition literally means "especially to murder(a human being)." Now, the very definition of murder itself means unlawfully killing someone with malice and aforethought. Therefore, I think it's important to understand that killing someone in self defense or to save children from a savage beating does not fall into this category. I think God knew very well what He meant when giving us the 10 commandments because of our fallen nature and foreknowledge to our circumstances therein.