A:

I suppose the first thing I should admit is that the Bible does not directly define ‘murder’.  Everything I say from here on out about the Bible’s view on it that doesn’t reference a specific verse is inferred, but I’ll be sure to explain how I came to it.

Those who translate the Bible do so very carefully.  I don’t actually know enough Hebrew to know whether or not the command specifically uses a word that means one kind of killing over another, but I trust that the translators do.  And murder, specifically, is defined as “the killing of another human being under conditions specifically covered in law”.  While it isn’t terribly helpful, the definition does highlight that murder requires specific circumstances, ordained by law.  So we start with these statements and build from there:

1.) The Law (capital ‘l’) exists to highlight sin and teach us about the nature of God.
2.) God cannot sin and will not command us to sin.
3.) God takes human lives in specific circumstances, includes the death penalty in the Law, and sends Israel to war or supports their warring on multiple occasions.
4.) War and the death penalty must be outside the scope of sin, at least in specific circumstances.

Now, we know that God does not abide injustice.  Which means that, in order for the death penalty or war to be supportable by Him, they must be just.  The governing body declaring war must be doing so with just cause and when methods of addressing the situation without loss of life have been exhausted.  The death penalty must be limited to crimes which warrant it and delivered in a manner which ensures, as best as possible, that the executed are actually guilty of those crimes.

All told, the realm of ‘killing that isn’t murder’ is incredibly narrow.  Now, you may not believe that our government has just cause for a given war, or that it doesn’t address the death penalty right, or even that no human government is capable of being just enough to carry out either.  That’s fine.  These things can be done without.  But if we’re going to use the Bible, we must admit that there is a window of permitted killing, however slim.  The argument “thou shalt not murder, therefore I oppose war” doesn’t actually stand up to scrutiny.  The argument “this war is unjust, therefore I cannot support it” or “this government is unjust, therefore I cannot support its wars” is entirely different and a rather good topic worth discussing.